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AgenticHypothesis: A Survey on Hypothesis Generation Using LLM Systems
Hypothesis Generation Large Language Models (LLMs) Retrieval Augmented Generation (RAG) Multi-agent Frameworks Iterative Refinement Techniques Scientific-domain Applications Evaluation Metrics
Hypothesis generation is a cornerstone of scientific discovery, enabling researchers to formulate testable ideas that drive innovation and progress. Although traditional methods have proven effective, they are often constrained by cognitive biases, information overload, and time limitations. Recently, the emergence of Large Language Models (LLMs) has introduced a promising approach to automate and enhance hypothesis generation. Trained on extensive datasets, these models have demonstrated the potential to generate novel, testable hypotheses across various domains. This review critically examines state-of-the-art methodologies for LLM-based hypothesis generation, including Retrieval Augmented Generation (RAG), multi-agent frameworks, and iterative refinement techniques. Applications in biomedical research, materials science, product innovation, and interdisciplinary studies are discussed, highlighting both the versatility and the impact of these systems. Despite their promise, LLMs also present challenges such as hallucinations, data biases, and ethical concerns, which necessitate careful implementation and oversight. Future research directions include refining model architectures, integrating multimodal capabilities, and establishing robust ethical frameworks to optimize the use of LLMs in scientific research. Overall, this review provides a balanced overview of how LLMs may enhance hypothesis generation while also addressing the associated challenges. The GitHub repository containing open-source LLM-empowered hypothesis generation systems is available at https://github.com/adibgpt/AgenticHypothesis.
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Evaluating AI Safety in Polish: An Automated Red-Teaming Approach
rainbow teaming safety llms red teaming
The development of multilingual large language models (LLMs) presents challenges in evaluating their safety across all supported languages. Enhancing safety in one language (e.g., English) may inadvertently introduce vulnerabilities in others. To address this issue, we propose a methodology for the automatic creation of red-teaming datasets for safety evaluation, categorizing them by risk type and attack style. We apply our methodology to the Polish language, highlighting the disparity between focusing on English and on Polish when generating safe outputs.
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Modeling Emergent Lexicon Formation with a Self-Reinforcing Stochastic Process
emergent language model entropy stochastic process
We introduce FiLex, a self-reinforcing stochastic process which models finite lexicons in emergent language experiments. The central property of FiLex is that it is a self-reinforcing process, parallel to the intuition that the more a word is used in a language, the more its use will continue. As a theoretical model, FiLex serves as a way to both explain and predict the behavior of the emergent language system. We empirically test FiLex's ability to capture the relationship between the emergent language's hyperparameters and the lexicon's Shannon entropy.
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Secure Byzantine-Robust Machine Learning
Byzantine robustness distributed learning secure aggregation
Increasingly machine learning systems are being deployed to edge servers and devices (e.g. mobile phones) and trained in a collaborative manner. Such distributed/federated/decentralized training raises a number of concerns about the robustness, privacy, and security of the procedure. While extensive work has been done in tackling with robustness, privacy, or security individually, their combination has rarely been studied. In this paper, we propose a secure multi-server protocol that offers both input privacy and Byzantine-robustness. In addition, this protocol is communication-efficient, fault-tolerant, and enjoys local differential privacy.
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Constructing Multiple High-Quality Deep Neural Networks: A TRUST-TECH Based Approach
Nonlinear Dynamical Systems Global Optimization Deep Neural Networks Ensemble.
The success of deep neural networks relied heavily on efficient stochastic gradient descent-like training methods. However, these methods are sensitive to initialization and hyper-parameters.
In this paper, a systematical method for finding multiple high-quality local optimal deep neural networks from a single training session, using the TRUST-TECH (TRansformation Under Stability-reTaining Equilibria Characterization) method, is introduced.
To realize effective TRUST-TECH searches to train deep neural networks on large datasets, a dynamic search paths (DSP) method is proposed to provide an improved search guidance in TRUST-TECH method.
The proposed DSP-TT method is implemented such that the computation graph remains constant during the search process, with only minor GPU memory overhead and requires just one training session to obtain multiple local optimal solutions (LOS). To take advantage of these LOSs, we also propose an improved ensemble method. Experiments on image classification datasets show that our method improves the testing performance by a substantial margin. Specifically, our fully-trained DSP-TT ResNet ensmeble improves the SGD baseline by 20\% (CIFAR10) and 15\%(CIFAR100). Furthermore, our method shows several advantages over other ensembling methods.
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CMAT: A Multi-Agent Collaboration Tuning Framework for Enhancing Small Language Models
Multi-Agent Collaboration Language Model Tuning Memory Adaptation
Open large language models (LLMs) have significantly advanced the field of natural language processing, showcasing impressive performance across various tasks.
Despite the significant advancements in LLMs, their effective operation still relies heavily on human input to accurately guide the dialogue flow, with agent tuning being a crucial optimization technique that involves human adjustments to the model for better response to such guidance.
Addressing this dependency, our work introduces the TinyAgent model, trained on a meticulously curated high-quality dataset.
We also present the Collaborative Multi-Agent Tuning (CMAT) framework, an innovative system designed to augment language agent capabilities through adaptive weight updates based on environmental feedback. This framework fosters collaborative learning and real-time adaptation among multiple intelligent agents, enhancing their context-awareness and long-term memory. In this research, we propose a new communication agent framework that integrates multi-agent systems with environmental feedback mechanisms, offering a scalable method to explore cooperative behaviors. Notably, our TinyAgent-7B model exhibits performance on par with GPT-3.5, despite having fewer parameters, signifying a substantial improvement in the efficiency and effectiveness of LLMs.
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Expressive yet Tractable Bayesian Deep Learning via Subnetwork Inference
expressive posterior approximations expressive subnetwork inference expressive subnetwork inference bayesian paradigm potential core issues modern deep learning poor calibration
The Bayesian paradigm has the potential to solve some of the core issues in modern deep learning, such as poor calibration, data inefficiency, and catastrophic forgetting. However, scaling Bayesian inference to the high-dimensional parameter spaces of deep neural networks requires restrictive approximations. In this paper, we propose performing inference over only a small subset of the model parameters while keeping all others as point estimates. This enables us to use expressive posterior approximations that would otherwise be intractable for the full model. In particular, we develop a practical and scalable Bayesian deep learning method that first trains a point estimate, and then infers a full covariance Gaussian posterior approximation over a subnetwork. We propose a subnetwork selection procedure which aims to maximally preserve posterior uncertainty. We empirically demonstrate the effectiveness of our approach compared to point-estimated networks and methods that use less expressive posterior approximations over the full network.
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Q-Value Weighted Regression: Reinforcement Learning with Limited Data
reinforcement learning rl offline rl continuous control atari sample efficiency
Sample efficiency and performance in the offline setting have emerged as among the main
challenges of deep reinforcement learning. We introduce Q-Value Weighted Regression (QWR),
a simple RL algorithm that excels in these aspects.
QWR is an extension of Advantage Weighted Regression (AWR), an off-policy actor-critic algorithm
that performs very well on continuous control tasks, also in the offline setting, but struggles
on tasks with discrete actions and in sample efficiency. We perform a theoretical analysis
of AWR that explains its shortcomings and use the insights to motivate QWR theoretically.
We show experimentally that QWR matches state-of-the-art algorithms both on tasks with
continuous and discrete actions. We study the main hyperparameters of QWR
and find that it is stable in a wide range of their choices and on different tasks.
In particular, QWR yields results on par with SAC on the MuJoCo suite and - with
the same set of hyperparameters -- yields results on par with a highly tuned Rainbow
implementation on a set of Atari games. We also verify that QWR performs well in the
offline RL setting, making it a compelling choice for reinforcement learning in domains
with limited data.
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WaNet - Imperceptible Warping-based Backdoor Attack
backdoor attack image warping wanet
With the thriving of deep learning and the widespread practice of using pre-trained networks, backdoor attacks have become an increasing security threat drawing many research interests in recent years. A third-party model can be poisoned in training to work well in normal conditions but behave maliciously when a trigger pattern appears. However, the existing backdoor attacks are all built on noise perturbation triggers, making them noticeable to humans. In this paper, we instead propose using warping-based triggers. The proposed backdoor outperforms the previous methods in a human inspection test by a wide margin, proving its stealthiness. To make such models undetectable by machine defenders, we propose a novel training mode, called the ``noise mode. The trained networks successfully attack and bypass the state-ofthe art defense methods on standard classification datasets, including MNIST, CIFAR-10, GTSRB, and CelebA. Behavior analyses show that our backdoors are transparent to network inspection, further proving this novel attack mechanism's efficiency.
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Redesigning the Classification Layer by Randomizing the Class Representation Vectors
classification layer representative vector target class vectors training visual similarities class vectors class representation vectors components first
Neural image classification models typically consist of two components. The first is an image encoder, which is responsible for encoding a given raw image into a representative vector. The second is the classification component, which is often implemented by projecting the representative vector onto target class vectors. The target class vectors, along with the rest of the model parameters, are estimated so as to minimize the loss function.
In this paper, we analyze how simple design choices for the classification layer affect the learning dynamics. We show that the standard cross-entropy training implicitly captures visual similarities between different classes, which might deteriorate accuracy or even prevents some models from converging. We propose to draw the class vectors randomly and set them as fixed during training, thus invalidating the visual similarities encoded in these vectors. We analyze the effects of keeping the class vectors fixed and show that it can increase the inter-class separability, intra-class compactness, and the overall model accuracy, while maintaining the robustness to image corruptions and the generalization of the learned concepts.
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Winning the L2RPN Challenge: Power Grid Management via Semi-Markov Afterstate Actor-Critic
power grid management deep reinforcement learning graph neural network
Safe and reliable electricity transmission in power grids is crucial for modern society. It is thus quite natural that there has been a growing interest in the automatic management of power grids, exemplified by the Learning to Run a Power Network Challenge (L2RPN), modeling the problem as a reinforcement learning (RL) task. However, it is highly challenging to manage a real-world scale power grid, mostly due to the massive scale of its state and action space. In this paper, we present an off-policy actor-critic approach that effectively tackles the unique challenges in power grid management by RL, adopting the hierarchical policy together with the afterstate representation. Our agent ranked first in the latest challenge (L2RPN WCCI 2020), being able to avoid disastrous situations while maintaining the highest level of operational efficiency in every test scenarios. This paper provides a formal description of the algorithmic aspect of our approach, as well as further experimental studies on diverse power grids.
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Maybe I Should Not Answer That, but... Do LLMs Understand The Safety of Their Inputs?
Large Language Models Unsafe Detection Inner Representations Safety
Ensuring the safety of the Large Language Model (LLM) is critical, but currently used methods in most cases sacrifice the model performance to obtain increased safety or perform poorly on data outside of their adaptation distribution. We investigate existing methods for such generalization and find them insufficient. Surprisingly, while even plain LLMs recognize unsafe prompts, they may still generate unsafe responses. To avoid performance degradation and preserve safe performance, we advocate for a two-step framework, where we first identify unsafe prompts via a lightweight classifier, and apply a "safe" model only to such prompts. In particular, we explore the design of the safety detector in more detail, investigating the use of different classifier architectures and prompting techniques. Interestingly, we find that the final hidden state for the last token is enough to provide robust performance, minimizing false positives on benign data while performing well on malicious prompt detection. Additionally, we show that classifiers trained on the representations from different model layers perform comparably on the latest model layers, indicating that safety representation is present in the LLMs' hidden states at most model stages. Our work is a step towards efficient, representation-based safety mechanisms for LLMs.
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Supervised Contrastive Learning for Pre-trained Language Model Fine-tuning
pre-trained language model fine-tuning supervised contrastive learning natural language understanding few-shot learning robustness generalization
State-of-the-art natural language understanding classification models follow two-stages: pre-training a large language model on an auxiliary task, and then fine-tuning the model on a task-specific labeled dataset using cross-entropy loss. However, the cross-entropy loss has several shortcomings that can lead to sub-optimal generalization and instability. Driven by the intuition that good generalization requires capturing the similarity between examples in one class and contrasting them with examples in other classes, we propose a supervised contrastive learning (SCL) objective for the fine-tuning stage. Combined with cross-entropy, our proposed SCL loss obtains significant improvements over a strong RoBERTa-Large baseline on multiple datasets of the GLUE benchmark in few-shot learning settings, without requiring specialized architecture, data augmentations, memory banks, or additional unsupervised data. Our proposed fine-tuning objective leads to models that are more robust to different levels of noise in the fine-tuning training data, and can generalize better to related tasks with limited labeled data.
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Modeling the Second Player in Distributionally Robust Optimization
distributionally robust optimization deep learning robustness adversarial learning
Distributionally robust optimization (DRO) provides a framework for training machine learning models that are able to perform well on a collection of related data distributions (the "uncertainty set"). This is done by solving a min-max game: the model is trained to minimize its maximum expected loss among all distributions in the uncertainty set. While careful design of the uncertainty set is critical to the success of the DRO procedure, previous work has been limited to relatively simple alternatives that keep the min-max optimization problem exactly tractable, such as $f$-divergence balls. In this paper, we argue instead for the use of neural generative models to characterize the worst-case distribution, allowing for more flexible and problem-specific selection of the uncertainty set. However, while simple conceptually, this approach poses a number of implementation and optimization challenges. To circumvent these issues, we propose a relaxation of the KL-constrained inner maximization objective that makes the DRO problem more amenable to gradient-based optimization of large scale generative models, and develop model selection heuristics to guide hyper-parameter search. On both toy settings and realistic NLP tasks, we find that the proposed approach yields models that are more robust than comparable baselines.
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Automatic Labeling of Data for Transfer Learning
transfer learning fine-tuning divergence pseudo labeling automated labeling experiments
Transfer learning uses trained weights from a source model as the initial weightsfor the training of a target dataset. A well chosen source with a large numberof labeled data leads to significant improvement in accuracy. We demonstrate atechnique that automatically labels large unlabeled datasets so that they can trainsource models for transfer learning. We experimentally evaluate this method, usinga baseline dataset of human-annotated ImageNet1K labels, against five variationsof this technique. We show that the performance of these automatically trainedmodels come within 17% of baseline on average.
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Self-supervised and Supervised Joint Training for Resource-rich Machine Translation
resource-rich machine translation neural machine translation pre-training self-supervised learning joint training
Self-supervised pre-training of text representations has been successfully applied to low-resource Neural Machine Translation (NMT). However, it usually fails to achieve notable gains on resource-rich NMT. In this paper, we propose a joint training approach, $F_2$-XEnDec, to combine self-supervised and supervised learning to optimize NMT models. To exploit complementary self-supervised signals for supervised learning, NMT models are trained on examples that are interbred from monolingual and parallel sentences through a new process called crossover encoder-decoder. Experiments on two resource-rich translation bench-marks, WMT’14 English-German and WMT’14 English-French, demonstrate that our approach achieves substantial improvements over a vanilla Transformer and obtains a new state of the art of 46 BLEU on English-French. Results also show that our approach is capable of improving model robustness against input perturbations which is known as a key weakness in contemporary NMT systems.
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Justified Trust in AI Fairness Assessment using Existing Metadata Entities
justified trust fairness transparency artefacts machine learning metadata fairness assessment
AI is becoming increasingly complex, opaque and connected to systems without human oversight. As such, ensuring trust in these systems has become challenging, yet vital. Trust is a multifaceted concept which varies over time and context, and to support users in making decisions on what to trust, work has been recently developed in the trustworthiness of systems. This includes examination of the security, privacy, safety and fairness of a system. In this work, we explore the fairness of AI systems. While mechanisms, such as formal verification, aim to guarantee properties such as fairness, their application in large-scale applications is rare due to cost and complexity issues. A major approach that is deployed in place of formal methods involves providing claims regarding the fairness of a system, with supporting evidence, to elicit justified trust in the system. Through continuous monitoring and transparent reporting of existing metadata with model experiment logs, organisations can provide reliable evidence for claims. This paper provides details of a new approach for evidence-based trust. We share our findings from a workshop with industry professionals and provide a practical example of how these concepts can be applied in a credit risk analysis system.
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Understanding Posterior Collapse in Generative Latent Variable Models
vae posterior collapse generative generative model latent variable probabilistic model pca ppca probabilistic pca
Posterior collapse in Variational Autoencoders (VAEs) arises when the variational distribution closely matches the uninformative prior for a subset of latent variables. This paper presents a simple and intuitive explanation for posterior collapse through the analysis of linear VAEs and their direct correspondence with Probabilistic PCA (pPCA). We identify how local maxima can emerge from the marginal log-likelihood of pPCA, which yields similar local maxima for the evidence lower bound (ELBO). We show that training a linear VAE with variational inference recovers a uniquely identifiable global maximum corresponding to the principal component directions. We provide empirical evidence that the presence of local maxima causes posterior collapse in deep non-linear VAEs. Our findings help to explain a wide range of heuristic approaches in the literature that attempt to diminish the effect of the KL term in the ELBO to reduce posterior collapse.
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LEAF: A Learnable Frontend for Audio Classification
audio understanding frontend learnable mel-filterbanks time-frequency representations sound classification
Mel-filterbanks are fixed, engineered audio features which emulate human perception and have been used through the history of audio understanding up to today. However, their undeniable qualities are counterbalanced by the fundamental limitations of handmade representations. In this work we show that we can train a single learnable frontend that outperforms mel-filterbanks on a wide range of audio signals, including speech, music, audio events and animal sounds, providing a general-purpose learned frontend for audio classification. To do so, we introduce a new principled, lightweight, fully learnable architecture that can be used as a drop-in replacement of mel-filterbanks. Our system learns all operations of audio features extraction, from filtering to pooling, compression and normalization, and can be integrated into any neural network at a negligible parameter cost. We perform multi-task training on eight diverse audio classification tasks, and show consistent improvements of our model over mel-filterbanks and previous learnable alternatives. Moreover, our system outperforms the current state-of-the-art learnable frontend on Audioset, with orders of magnitude fewer parameters.
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Privacy Auditing for Large Language Models with Natural Identifiers
LLMs canaries data inference
The privacy auditing for large language models (LLMs) faces significant challenges. Membership inference attacks, once considered a practical privacy auditing tool, are unreliable for pretrained LLMs due to the lack of non-member data from the same distribution as the member data. Exacerbating the situation further, the dataset inference cannot be performed without such a non-member set. Finally, we lack a formal post hoc auditing of training privacy guarantees. Previous differential privacy auditing methods are impractical since they rely on inserting specially crafted canary data *during training*, making audits on already pre-trained LLMs impossible without expensive retraining. This work introduces **natural identifiers (NIDs)** as a novel solution to these challenges. NIDs are structured random strings, such as SSH keys, cryptographic hashes, and shortened URLs, which naturally occur in common LLM training datasets. Their format enables the generation of unlimited additional random strings from the same distribution, which can act as non-members or alternative canaries for audit. Leveraging this property, we show how NIDs support robust evaluation of membership inference attacks, enable dataset inference for any suspect set containing NIDs, and facilitate post hoc privacy auditing without retraining.
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Neural Context Flows for Learning Generalizable Dynamical Systems
Neural ODE Meta-Learning Dynamical Systems Scientific Machine Learning
Neural Ordinary Differential Equations typically struggle to generalize to new dynamical behaviors created by parameter changes in the underlying system, even when the dynamics are close to previously seen behaviors. The issue gets worse when the changing parameters are unobserved, i.e., their value or influence is not directly measurable when collecting data. We introduce Neural Context Flow (NCF), a framework that encodes said unobserved parameters in a latent context vector as input to a vector field. NCFs leverage differentiability of the vector field with respect to the parameters, along with first-order Taylor expansion to allow any context vector to influence trajectories from other parameters. We validate our method and compare it to established Multi-Task and Meta-Learning alternatives, showing competitive performance in mean squared error for in-domain and out-of-distribution evaluation on the Lotka-Volterra, Glycolytic Oscillator, and Gray-Scott problems. This study holds practical implications for foundational models in science and related areas that benefit from conditional neural ODEs. Our code is openly available at \url{https://github.com/ddrous/ncflow}.
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Detecting Unreliable Responses in Generative Vision-Language Models via Visual Uncertainty
Visual Uncertainty
Building trust in vision-language models (VLMs) requires reliable uncertainty estimation (UE) to detect unreliable generations. Existing UE approaches often require access to internal model representations to train an uncertainty estimator, which may not always be feasible. Black-box methods primarily rely on language-based augmentations, such as question rephrasings or sub-question modules, to detect unreliable generations. However, the role of visual information in UE remains largely underexplored. To study this aspect of the UE research problem, we investigate a visual contrast approach that perturbs input images by removing visual evidence relevant to the question and measures changes in the output distribution. We hypothesize that for unreliable generations, the output token distributions from an augmented and unaugmented image remain similar despite the removal of key visual information in the augmented image. We evaluate this method on the A-OKVQA dataset using four popular pre-trained VLMs. Our results demonstrate that visual contrast, even when applied only at the first token, can be as effective as—if not always superior to—existing state-of-the-art probability-based black-box methods.
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A statistical theory of cold posteriors in deep neural networks
Bayesian inference cold posteriors sgld
To get Bayesian neural networks to perform comparably to standard neural networks it is usually necessary to artificially reduce uncertainty using a tempered or cold posterior. This is extremely concerning: if the prior is accurate, Bayes inference/decision theory is optimal, and any artificial changes to the posterior should harm performance. While this suggests that the prior may be at fault, here we argue that in fact, BNNs for image classification use the wrong likelihood. In particular, standard image benchmark datasets such as CIFAR-10 are carefully curated. We develop a generative model describing curation which gives a principled Bayesian account of cold posteriors, because the likelihood under this new generative model closely matches the tempered likelihoods used in past work.
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Mapping the Timescale Organization of Neural Language Models
natural language processing LSTM timescale hierarchy temporal context
In the human brain, sequences of language input are processed within a distributed and hierarchical architecture, in which higher stages of processing encode contextual information over longer timescales. In contrast, in recurrent neural networks which perform natural language processing, we know little about how the multiple timescales of contextual information are functionally organized. Therefore, we applied tools developed in neuroscience to map the “processing timescales” of individual units within a word-level LSTM language model. This timescale-mapping method assigned long timescales to units previously found to track long-range syntactic dependencies. Additionally, the mapping revealed a small subset of the network (less than 15% of units) with long timescales and whose function had not previously been explored. We next probed the functional organization of the network by examining the relationship between the processing timescale of units and their network connectivity. We identified two classes of long-timescale units: “controller” units composed a densely interconnected subnetwork and strongly projected to the rest of the network, while “integrator” units showed the longest timescales in the network, and expressed projection profiles closer to the mean projection profile. Ablating integrator and controller units affected model performance at different positions within a sentence, suggesting distinctive functions of these two sets of units. Finally, we tested the generalization of these results to a character-level LSTM model and models with different architectures. In summary, we demonstrated a model-free technique for mapping the timescale organization in recurrent neural networks, and we applied this method to reveal the timescale and functional organization of neural language models
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Random Network Distillation as a Diversity Metric for Both Image and Text Generation
GAN NLP ImageNet generative diversity VAE CelebA language model
Generative models are increasingly able to produce remarkably high quality images and text. The community has developed numerous evaluation metrics for comparing generative models. However, these metrics do not effectively quantify data diversity. We develop a new diversity metric that can readily be applied to data, both synthetic and natural, of any type. Our method employs random network distillation, a technique introduced in reinforcement learning. We validate and deploy this metric on both images and text. We further explore diversity in few-shot image generation, a setting which was previously difficult to evaluate.
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Ground-Truth Adversarial Examples
adversarial examples neural networks formal verification ground truths
The ability to deploy neural networks in real-world, safety-critical systems is severely limited by the presence of adversarial examples: slightly perturbed inputs that are misclassified by the network. In recent years, several techniques have been proposed for training networks that are robust to such examples; and each time stronger attacks have been devised, demonstrating the shortcomings of existing defenses. This highlights a key difficulty in designing an effective defense: the inability to assess a network's robustness against future attacks. We propose to address this difficulty through formal verification techniques. We construct ground truths: adversarial examples with a provably-minimal distance from a given input point. We demonstrate how ground truths can serve to assess the effectiveness of attack techniques, by comparing the adversarial examples produced by those attacks to the ground truths; and also of defense techniques, by computing the distance to the ground truths before and after the defense is applied, and measuring the improvement. We use this technique to assess recently suggested attack and defense techniques.
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Model-based Asynchronous Hyperparameter and Neural Architecture Search
Bayesian Optimization AutoML Hyperparameter Optimization Neural Architecture Search
We introduce a model-based asynchronous multi-fidelity method for hyperparameter and neural architecture search that combines the strengths of asynchronous Successive Halving and Gaussian process-based Bayesian optimization. At the heart of our method is a probabilistic model that can simultaneously reason across hyperparameters and resource levels, and supports decision-making in the presence of pending evaluations. We demonstrate the effectiveness of our method on a wide range of challenging benchmarks, for tabular data, image classification and language modelling, and report substantial speed-ups over current state-of-the-art methods. Our new methods, along with asynchronous baselines, are implemented in a distributed framework which will be open sourced along with this publication.
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Single Layers of Attention Suffice to Predict Protein Contacts
Protein Structure Proteins Contact Prediction Representation Learning Language Modeling Attention Transformer BERT Markov Random Fields Potts Models Self-supervised learning
The established approach to unsupervised protein contact prediction estimates coevolving positions using undirected graphical models. This approach trains a Potts model on a Multiple Sequence Alignment, then predicts that the edges with highest weight correspond to contacts in the 3D structure. On the other hand, increasingly large Transformers are being pretrained on protein sequence databases but have demonstrated mixed results for downstream tasks, including contact prediction. This has sparked discussion about the role of scale and attention-based models in unsupervised protein representation learning. We argue that attention is a principled model of protein interactions, grounded in real properties of protein family data. We introduce a simplified attention layer, factored attention, and show that it achieves comparable performance to Potts models, while sharing parameters both within and across families. Further, we extract contacts from the attention maps of a pretrained Transformer and show they perform competitively with the other two approaches. This provides evidence that large-scale pretraining can learn meaningful protein features when presented with unlabeled and unaligned data. We contrast factored attention with the Transformer to indicate that the Transformer leverages hierarchical signal in protein family databases not captured by our single-layer models. This raises the exciting possibility for the development of powerful structured models of protein family databases.
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A Seed-Augment-Train Framework for Universal Digit Classification
Transfer learning Generative models digit classification domain transfer
In this paper, we propose a Seed-Augment-Train/Transfer (SAT) framework that contains a synthetic seed image dataset generation procedure for languages with different numeral systems using freely available open font file datasets. This seed dataset of images is then augmented to create a purely synthetic training dataset, which is in turn used to train a deep neural network and test on held-out real world handwritten digits dataset spanning five Indic scripts, Kannada, Tamil, Gujarati, Malayalam, and Devanagari. We showcase the efficacy of this approach both qualitatively, by training a Boundary-seeking GAN (BGAN) that generates realistic digit images in the five languages, and also qualitatively by testing a CNN trained on the synthetic data on the real-world datasets. This establishes not only an interesting nexus between the font-datasets-world and transfer learning but also provides a recipe for universal-digit classification in any script.
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Weak Supervision for Time Series: Wearable Sensor Classification with Limited Labeled Data
wearable sensors weak supervision time series Parkinsons
Using modern deep learning models to make predictions on time series data from wearable sensors generally requires large amounts of labeled data. However, labeling these large datasets can be both cumbersome and costly. In this paper, we apply weak supervision to time series data, and programmatically label a dataset from sensors worn by patients with Parkinson's. We then built a LSTM model that predicts when these patients exhibit clinically relevant freezing behavior (inability to make effective forward stepping). We show that (1) when our model is trained using patient-specific data (prior sensor sessions), we come within 9% AUROC of a model trained using hand-labeled data and (2) when we assume no prior observations of subjects, our weakly supervised model matched performance with hand-labeled data. These results demonstrate that weak supervision may help reduce the need to painstakingly hand label time series training data.
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Systematic Analysis of Cluster Similarity Indices: How to Validate Validation Measures
cluster similarity indices cluster validation clustering community detection constant baseline
There are many cluster similarity indices used to evaluate clustering algorithms, and choosing the best one for a particular task remains an open problem. We demonstrate that this problem is crucial: there are many disagreements among the indices, these disagreements do affect which algorithms are chosen in applications, and this can lead to degraded performance in real-world systems. We propose a theoretical solution to this problem: we develop a list of desirable properties and theoretically verify which indices satisfy them. This allows for making an informed choice: given a particular application, one can first make a selection of properties that are desirable for a given application and then identify indices satisfying these. We observe that many popular indices have significant drawbacks. Instead, we advocate using other ones that are not so widely adopted but have beneficial properties.
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Improved Image Generation via Sparsity
Sparse Coding Image Generation
The interest of the deep learning community in image synthesis has grown massively in recent years. Nowadays, deep generative methods, and specifically Generative Adversarial Networks (GANs),
are leading to state-of-the-art performance, capable of synthesizing images that appear realistic.
While the efforts for improving the quality of the generated images are extensive, most attempts still consider the generator part as an uncorroborated "black-box".
In this paper, we aim to provide a better understanding of the image generation process. We interpret existing generators as implicitly relying on sparsity-inspired models.
More specifically, we show that generators can be viewed as manifestations of the Convolutional Sparse Coding (CSC) and its Multi-Layered version (ML-CSC) synthesis processes.
We leverage this observation by explicitly enforcing a sparsifying regularization on appropriately chosen activation layers in the generator and demonstrate that this leads to improved image synthesis. Furthermore, we show that the same rationale and benefits apply to generators serving inverse problems, demonstrated on the Deep Image Prior (DIP) method.
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No, Of Course I Can! Refusal Mechanisms Can Be Exploited Using Harmless Data
red-teaming fine-tuning attacks data poisoning
Leading language model (LM) providers like OpenAI and Google offer fine-tuning APIs that allow customers to adapt LMs for specific use cases. To prevent misuse, these LM providers implement filtering mechanisms to block harmful fine-tuning data. Consequently, adversaries seeking to produce unsafe LMs via these APIs must craft adversarial training data that are not identifiably harmful. We make three contributions in this context: 1. We show that many existing attacks that use harmless data to create unsafe LMs rely on eliminating model refusals in the first few tokens of their responses. 2. We show that such prior attacks can be blocked by a simple defense that pre-fills the first few tokens from an aligned model before letting the fine-tuned model fill in the rest. 3. We describe a new data-poisoning attack, ``No, Of course I Can Execute'' (NOICE), which exploits an LM's formulaic refusal mechanism to elicit harmful responses. By training an LM to refuse benign requests on the basis of safety before fulfilling those requests regardless, we are able to jailbreak several open-source models and a closed-source model (GPT-4o). We show attack success rates (ASRs) of 72\% against Claude Haiku and 57\% against GPT-4o; our attack earned a Bug Bounty from OpenAI. Against open-source models protected by simple defenses, we improve ASRs by a factor of $3.5$ times compared to other attacks that use only harmless data. NOICE demonstrates the exploitability of repetitive refusal mechanisms and broadens understanding of the threats closed-source models face from harmless data.
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Fine-Tuning Offline Reinforcement Learning with Model-Based Policy Optimization
Offline Reinforcement Learning Model-Based Reinforcement Learning Off-policy Reinforcement Learning uncertainty estimation
In offline reinforcement learning (RL), we attempt to learn a control policy from a fixed dataset of environment interactions. This setting has the potential benefit of allowing us to learn effective policies without needing to collect additional interactive data, which can be expensive or dangerous in real-world systems. However, traditional off-policy RL methods tend to perform poorly in this setting due to the distributional shift between the fixed data set and the learned policy. In particular, they tend to extrapolate optimistically and overestimate the action-values outside of the dataset distribution. Recently, two major avenues have been explored to address this issue. First, behavior-regularized methods that penalize actions that deviate from the demonstrated action distribution. Second, uncertainty-aware model-based (MB) methods that discourage state-actions where the dynamics are uncertain. In this work, we propose an algorithmic framework that consists of two stages. In the first stage, we train a policy using behavior-regularized model-free RL on the offline dataset. Then, a second stage where we fine-tune the policy using our novel Model-Based Behavior-Regularized Policy Optimization (MB2PO) algorithm. We demonstrate that for certain tasks and dataset distributions our conservative model-based fine-tuning can greatly increase performance and allow the agent to generalize and outperform the demonstrated behavior. We evaluate our method on a variety of the Gym-MuJoCo tasks in the D4RL benchmark and demonstrate that our method is competitive and in some cases superior to the state of the art for most of the evaluated tasks.
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Weights Having Stable Signs Are Important: Finding Primary Subnetworks and Kernels to Compress Binary Weight Networks
bwns weight signs training stable signs important finding primary subnetworks kernels binary weight networks ste factors
Binary Weight Networks (BWNs) have significantly lower computational and memory costs compared to their full-precision counterparts. To address the non-differentiable issue of BWNs, existing methods usually use the Straight-Through-Estimator (STE). In the optimization, they learn optimal binary weight outputs represented as a combination of scaling factors and weight signs to approximate 32-bit floating-point weight values, usually with a layer-wise quantization scheme. In this paper, we begin with an empirical study of training BWNs with STE under the settings of using common techniques and tricks. We show that in the context of using batch normalization after convolutional layers, adapting scaling factors with either hand-crafted or learnable methods brings marginal or no accuracy gain to final model, while the change of weight signs is crucial in the training of BWNs. Furthermore, we observe two astonishing training phenomena. Firstly, the training of BWNs demonstrates the process of seeking primary binary sub-networks whose weight signs are determined and fixed at the early training stage, which is akin to recent findings on the lottery ticket hypothesis for efficient learning of sparse neural networks. Secondly, we find binary kernels in the convolutional layers of final models tend to be centered on a limited number of the most frequent binary kernels, showing binary weight networks may has the potential to be further compressed, which breaks the common wisdom that representing each weight with a single bit puts the quantization to the extreme compression. To testify this hypothesis, we additionally propose a binary kernel quantization method, and we call resulting models Quantized Binary-Kernel Networks (QBNs). We hope these new experimental observations would shed new design insights to improve the training and broaden the usages of BWNs.
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Learning Value Functions in Deep Policy Gradients using Residual Variance
critic value functions deep policy gradients algorithms resp residual variance successful diverse decision making control tasks
Policy gradient algorithms have proven to be successful in diverse decision making and control tasks. However, these methods suffer from high sample complexity and instability issues. In this paper, we address these challenges by providing a different approach for training the critic in the actor-critic framework. Our work builds on recent studies indicating that traditional actor-critic algorithms do not succeed in fitting the true value function, calling for the need to identify a better objective for the critic. In our method, the critic uses a new state-value (resp. state-action-value) function approximation that learns the value of the states (resp. state-action pairs) relative to their mean value rather than the absolute value as in conventional actor-critic. We prove the theoretical consistency of the new gradient estimator and observe dramatic empirical improvement across a variety of continuous control tasks and algorithms. Furthermore, we validate our method in tasks with sparse rewards, where we provide experimental evidence and theoretical insights.
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On the geometry of generalization and memorization in deep neural networks
deep learning theory representation learning statistical physics methods double descent
Understanding how large neural networks avoid memorizing training data is key to explaining their high generalization performance. To examine the structure of when and where memorization occurs in a deep network, we use a recently developed replica-based mean field theoretic geometric analysis method. We find that all layers preferentially learn from examples which share features, and link this behavior to generalization performance. Memorization predominately occurs in the deeper layers, due to decreasing object manifolds’ radius and dimension, whereas early layers are minimally affected. This predicts that generalization can be restored by reverting the final few layer weights to earlier epochs before significant memorization occurred, which is confirmed by the experiments. Additionally, by studying generalization under different model sizes, we reveal the connection between the double descent phenomenon and the underlying model geometry. Finally, analytical analysis shows that networks avoid memorization early in training because close to initialization, the gradient contribution from permuted examples are small. These findings provide quantitative evidence for the structure of memorization across layers of a deep neural network, the drivers for such structure, and its connection to manifold geometric properties.
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Collaborative Filtering with Smooth Reconstruction of the Preference Function
collaborative filtering recommender system sampling theory
The problem of predicting the rating of a set of users to a set of items in a recommender system based on partial knowledge of the ratings is widely known as collaborative filtering. In this paper, we consider a mapping of the items into a vector space and study the prediction problem by assuming an underlying smooth preference function for each user, the quantization at each given vector yields the associated rating. To estimate the preference functions, we implicitly cluster the users with similar ratings to form dominant types. Next, we associate each dominant type with a smooth preference function; i.e., the function values for items with nearby vectors shall be close to each other.
The latter is accomplished by a rich representation learning in a so-called frequency domain. In this framework, we propose two approaches for learning user and item representations. First, we use an alternating optimization method in the spirit of $k$-means to cluster users and map items. We further make this approach less prone to overfitting by a boosting technique.
Second, we present a feedforward neural network architecture consisting of interpretable layers which implicitely clusters the users. The performance of the method is evaluated on two benchmark datasets (ML-100k and ML-1M). Albeit the method benefits from simplicity, it shows a remarkable performance and opens a venue for future research. All codes are publicly available on the GitLab.
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Graphical Residual Flows
Normalizing flow Bayesian network density estimation inference
Graphical flows add further structure to normalizing flows by encoding non-trivial variable dependencies. Previous graphical flow models have focused primarily on a single flow direction: the normalizing direction for density estimation, or the generative direction for inference. However, to use a single flow to perform tasks in both directions, the model must exhibit stable and efficient flow inversion. This work introduces graphical residual flows, a graphical flow based on invertible residual networks. Our approach to incorporating dependency information in the flow, means that we are able to calculate the Jacobian determinant of these flows exactly. Our experiments confirm that graphical residual flows provide stable and accurate inversion that is also more time-efficient than alternative flows with similar task performance. Furthermore, our model provides performance competitive with other graphical flows for both density estimation and inference tasks.
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Learning a Max-Margin Classifier for Cross-Domain Sentiment Analysis
natural language processing sentiment analysis cross-domain data representation distribution alignment
Sentiment analysis is a costly yet necessary task for enterprises to study the opinions of their costumers to improve their products and services and to determine optimal marketing strategies. Due to existence of a wide range of domains across different products and services, cross-domain sentiment analysis methods have received significant attention in recent years. These methods mitigate the domain gap between different applications by training cross-domain generalizable classifiers which help to relax the need for individual data annotation per each domain. Most existing methods focus on learning domain-agnostic representations that are invariant with respect to both the source and the target domains. As a result, a classifier that is trained using annotated data in a source domain, would generalize well in a related target domain. In this work, we introduce a new domain adaptation method which induces large margins between different classes in an embedding space based on the notion of prototypical distribution. This embedding space is trained to be domain-agnostic by matching the data distributions across the domains. Large margins in the source domain help to reduce the effect of ``domain shift'' on the performance of a trained classifier in the target domain. Theoreticaland empirical analysis are provided to demonstrate that the method is effective.
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Monotonic neural network: combining deep learning with domain knowledge for chiller plants energy optimization
domain knowledge combining deep learning monotonic neural network interested deep learning framework hotspot applications deep learning
In this paper, we are interested in building a domain knowledge based deep learning framework to solve the chiller plants energy optimization problems. Compared to the hotspot applications of deep learning (e.g. image classification and NLP), it is difficult to collect enormous data for deep network training in real-world physical systems. Most existing methods reduce the complex systems into linear model to facilitate the training on small samples. To tackle the small sample size problem, this paper considers domain knowledge in the structure and loss design of deep network to build a nonlinear model with lower redundancy function space. Specifically, the energy consumption estimation of most chillers can be physically viewed as an input-output monotonic problem. Thus, we can design a Neural Network with monotonic constraints to mimic the physical behavior of the system. We verify the proposed method in a cooling system of a data center, experimental results show the superiority of our framework in energy optimization compared to the existing ones.
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A RAD approach to deep mixture models
discrete variables generative models flow based models
Flow based models such as Real NVP are an extremely powerful approach to density estimation. However, existing flow based models are restricted to transforming continuous densities over a continuous input space into similarly continuous distributions over continuous latent variables. This makes them poorly suited for modeling and representing discrete structures in data distributions, for example class membership or discrete symmetries. To address this difficulty, we present a normalizing flow architecture which relies on domain partitioning using locally invertible functions, and possesses both real and discrete valued latent variables. This Real and Discrete (RAD) approach retains the desirable normalizing flow properties of exact sampling, exact inference, and analytically computable probabilities, while at the same time allowing simultaneous modeling of both continuous and discrete structure in a data distribution.
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Neural Architecture Search without Training
NAS efficiency search fast cheap convnets
The time and effort involved in hand-designing deep neural networks is immense. This has prompted the development of Neural Architecture Search (NAS) techniques to automate this design. However, NAS algorithms tend to be slow and expensive; they need to train vast numbers of candidate networks to inform the search process. This could be remedied if we could infer a network's trained accuracy from its initial state. In this work, we examine the correlation of linear maps induced by augmented versions of a single image in untrained networks and motivate how this can be used to give a measure which is highly indicative of a network’s trained performance. We incorporate this measure into a simple algorithm that allows us to search for powerful networks without any training in a matter of seconds on a single GPU, and verify its effectiveness on NAS-Bench-101 and NAS-Bench-201. Finally, we show that our approach can be readily combined with more expensive search methods for added value: we modify regularised evolutionary search to produce a novel algorithm that outperforms its predecessor.
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Emergent communication in human-machine games
Emergent Communication Multi Agent Systems Reinforcement Learning
In this paper, we present how Emergent Communication (EmeCom) literature can be used to characterize a subset of human communication ability using recurrent features.
EmeCom does not directly require human involvement; however, we advocate that the entire field spawned from a desire to achieve human-machine interaction and that explicitly considering human-AI interaction is an important research direction. Our goal is to bring emergent communication researchers together by demonstrating that different approaches can be regarded as subsets of the same problem. Also, we recognize the importance of incorporating other aspects of human interaction into this field.
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Revisiting Locally Supervised Learning: an Alternative to End-to-end Training
Locally supervised training Deep learning
Due to the need to store the intermediate activations for back-propagation, end-to-end (E2E) training of deep networks usually suffers from high GPUs memory footprint. This paper aims to address this problem by revisiting the locally supervised learning, where a network is split into gradient-isolated modules and trained with local supervision. We experimentally show that simply training local modules with E2E loss tends to collapse task-relevant information at early layers, and hence hurts the performance of the full model. To avoid this issue, we propose an information propagation (InfoPro) loss, which encourages local modules to preserve as much useful information as possible, while progressively discard task-irrelevant information. As InfoPro loss is difficult to compute in its original form, we derive a feasible upper bound as a surrogate optimization objective, yielding a simple but effective algorithm. In fact, we show that the proposed method boils down to minimizing the combination of a reconstruction loss and a normal cross-entropy/contrastive term. Extensive empirical results on five datasets (i.e., CIFAR, SVHN, STL-10, ImageNet and Cityscapes) validate that InfoPro is capable of achieving competitive performance with less than 40% memory footprint compared to E2E training, while allowing using training data with higher-resolution or larger batch sizes under the same GPU memory constraint. Our method also enables training local modules asynchronously for potential training acceleration.
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Max-sliced Bures Distance for Interpreting Discrepancies
covariance covariate shift distance metrics divergence generative adversarial networks interpretable approaches kernel methods probability metric RKHS
We propose the max-sliced Bures distance, a lower bound on the max-sliced Wasserstein-2 distance, to identify the instances associated with the maximum discrepancy between two samples. The max-slicing can be decomposed into two asymmetric divergences each expressed in terms of an optimal slice or equivalently a witness function that has large magnitude evaluations on a localized subset of instances in one distribution versus the other. We show how witness functions can be used to detect and correct for covariate shift through reweighting and to evaluate generative adversarial networks. Unlike heuristic algorithms for the max-sliced Wasserstein-2 distance that may fail to find the optimal slice, we detail a tractable algorithm that finds the global optimal slice and scales to large sample sizes. As the Bures distance quantifies differences in covariance, we generalize the max-sliced Bures distance by using non-linear mappings, enabling it to capture changes in higher-order statistics. We explore two types of non-linear mappings: positive semidefinite kernels where the witness functions belong to a reproducing kernel Hilbert space, and task-relevant mappings corresponding to a neural network. In the context of samples of natural images, our approach provides an interpretation of the Fréchet Inception distance by identifying the synthetic and natural instances that are either over-represented or under-represented with respect to the other sample. We apply the proposed measure to detect imbalances in class distributions in various data sets and to critique generative models.
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Searching for Activation Functions
meta learning activation functions
The choice of activation functions in deep networks has a significant effect on the training dynamics and task performance. Currently, the most successful and widely-used activation function is the Rectified Linear Unit (ReLU). Although various hand-designed alternatives to ReLU have been proposed, none have managed to replace it due to inconsistent gains. In this work, we propose to leverage automatic search techniques to discover new activation functions. Using a combination of exhaustive and reinforcement learning-based search, we discover multiple novel activation functions. We verify the effectiveness of the searches by conducting an empirical evaluation with the best discovered activation function. Our experiments show that the best discovered activation function, f(x) = x * sigmoid(beta * x), which we name Swish, tends to work better than ReLU on deeper models across a number of challenging datasets. For example, simply replacing ReLUs with Swish units improves top-1 classification accuracy on ImageNet by 0.9% for Mobile NASNet-A and 0.6% for Inception-ResNet-v2. The simplicity of Swish and its similarity to ReLU make it easy for practitioners to replace ReLUs with Swish units in any neural network.
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Domain Adaptation with Asymmetrically-Relaxed Distribution Alignment
domain adaptation distribution alignment adversarial training theory
Domain adaptation addresses the common problem when the target distribution generating our test data drifts from the source (training) distribution. While absent assumptions, domain adaptation is impossible, strict conditions, e.g. covariate or label shift, enable principled algorithms. Recently-proposed domain-adversarial approaches consist of aligning source and target encodings, often motivating this approach as minimizing two (of three) terms in a theoretical bound on target error. Unfortunately, this minimization can cause arbitrary increases in the third term, e.g. they can break down under shifting label distributions. We propose asymmetrically-relaxed distribution alignment, a new approach that overcomes some limitations of standard domain-adversarial algorithms. Moreover, we characterize precise assumptions under which our algorithm is theoretically principled and demonstrate empirical benefits on both synthetic and real datasets.
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Non-Markovian Predictive Coding For Planning In Latent Space
representation learning reinforcement learning information theory
High-dimensional observations are a major challenge in the application of model-based reinforcement learning (MBRL) to real-world environments. In order to handle high-dimensional sensory inputs, existing MBRL approaches use representation learning to map high-dimensional observations into a lower-dimensional latent space that is more amenable to dynamics estimation and planning. Crucially, the task-relevance and predictability of the learned representations play critical roles in the success of planning in latent space. In this work, we present Non-Markovian Predictive Coding (NMPC), an information-theoretic approach for planning from high-dimensional observations with two key properties: 1) it formulates a mutual information objective that prioritizes the encoding of task-relevant components of the environment; and 2) it employs a recurrent neural network capable of modeling non-Markovian latent dynamics. To demonstrate NMPC’s ability to prioritize task-relevant information, we evaluate our new model on a challenging modification of standard DMControl tasks where the DMControl background is replaced with natural videos, containing complex but irrelevant information to the planning task. Our experiments show that NMPC is superior to existing methods in the challenging complex-background setting while remaining competitive with current state-of-the-art MBRL models in the standard setting.
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Privacy-preserving Learning via Deep Net Pruning
Neural Network Pruning Differential Privacy
Neural network pruning has demonstrated its success in significantly improving the computational efficiency of deep models while only introducing a small reduction on final accuracy. In this paper, we explore an extra bonus of neural network pruning in terms of enhancing privacy. Specifically, we show a novel connection between magnitude-based pruning and adding differentially private noise to intermediate layers under the over-parameterized regime. To the best of our knowledge, this is the first work that bridges pruning with the theory of differential privacy. The paper also presents experimental results by running the model inversion attack on two benchmark datasets, which supports the theoretical finding.
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An Efficient Protocol for Distributed Column Subset Selection in the Entrywise $\ell_p$ Norm
Column Subset Selection Distributed Learning
We give a distributed protocol with nearly-optimal communication and number of rounds for Column Subset Selection with respect to the entrywise {$\ell_1$} norm ($k$-CSS$_1$), and more generally, for the $\ell_p$-norm with $1 \leq p < 2$. We study matrix factorization in $\ell_1$-norm loss, rather than the more standard Frobenius norm loss, because the $\ell_1$ norm is more robust to noise, which is observed to lead to improved performance in a wide range of computer vision and robotics problems.
In the distributed setting, we consider $s$ servers in the standard coordinator model of communication, where the columns of the input matrix $A \in \mathbb{R}^{d \times n}$ ($n \gg d$) are distributed across the $s$ servers. We give a protocol in this model with $\widetilde{O}(sdk)$ communication, $1$ round, and polynomial running time, and which achieves a multiplicative $k^{\frac{1}{p} - \frac{1}{2}}\poly(\log nd)$-approximation to the best possible column subset. A key ingredient in our proof is the reduction to the $\ell_{p,2}$-norm, which corresponds to the $p$-norm of the vector of Euclidean norms of each of the columns of $A$. This enables us to use strong coreset constructions for Euclidean norms, which previously had not been used in this context. This naturally also allows us to implement our algorithm in the popular streaming model of computation. We further propose a greedy algorithm for selecting columns, which can be used by the coordinator, and show the first provable guarantees for a greedy algorithm for the $\ell_{1,2}$ norm. Finally, we implement our protocol and give significant practical advantages on real-world data analysis tasks.
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Global Node Attentions via Adaptive Spectral Filters
Graph Representation learning Graph Convolutional Network Graph Fourier transform
Graph neural networks (GNNs) have been extensively studied for prediction tasks on graphs. Most GNNs assume local homophily, i.e., strong similarities in local neighborhoods. This assumption limits the generalizability of GNNs, which has been demonstrated by recent work on disassortative graphs with weak local homophily. In this paper, we argue that GNN's feature aggregation scheme can be made flexible and adaptive to data without the assumption of local homophily. To demonstrate, we propose a GNN model with a global self-attention mechanism defined using learnable spectral filters, which can attend to any nodes, regardless of distance. We evaluated the proposed model on node classification tasks over six benchmark datasets. The proposed model has been shown to generalize well to both assortative and disassortative graphs. Further, it outperforms all state-of-the-art baselines on disassortative graphs and performs comparably with them on assortative graphs.
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Critical Points of Linear Neural Networks: Analytical Forms and Landscape Properties
neural networks critical points analytical form landscape
Due to the success of deep learning to solving a variety of challenging machine learning tasks, there is a rising interest in understanding loss functions for training neural networks from a theoretical aspect. Particularly, the properties of critical points and the landscape around them are of importance to determine the convergence performance of optimization algorithms. In this paper, we provide a necessary and sufficient characterization of the analytical forms for the critical points (as well as global minimizers) of the square loss functions for linear neural networks. We show that the analytical forms of the critical points characterize the values of the corresponding loss functions as well as the necessary and sufficient conditions to achieve global minimum. Furthermore, we exploit the analytical forms of the critical points to characterize the landscape properties for the loss functions of linear neural networks and shallow ReLU networks. One particular conclusion is that: While the loss function of linear networks has no spurious local minimum, the loss function of one-hidden-layer nonlinear networks with ReLU activation function does have local minimum that is not global minimum.
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An Empirical Study of the Expressiveness of Graph Kernels and Graph Neural Networks
graph kernels graph neural networks graphs empirical study expressiveness expressive power studies algorithms neural networks great success
Graph neural networks and graph kernels have achieved great success in solving machine learning problems on graphs. Recently, there has been considerable interest in determining the expressive power mainly of graph neural networks and of graph kernels, to a lesser extent. Most studies have focused on the ability of these approaches to distinguish non-isomorphic graphs or to identify specific graph properties. However, there is often a need for algorithms whose produced graph representations can accurately capture similarity/distance of graphs. This paper studies the expressive power of graph neural networks and graph kernels from an empirical perspective. Specifically, we compare the graph representations and similarities produced by these algorithms against those generated by a well-accepted, but intractable graph similarity function. We also investigate the impact of node attributes on the performance of the different models and kernels. Our results reveal interesting findings. For instance, we find that theoretically more powerful models do not necessarily yield higher-quality representations, while graph kernels are shown to be very competitive with graph neural networks.
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AstroAgents: A Multi-Agent AI for Hypothesis Generation from Mass Spectrometry Data
Multi-Agent Systems Mass Spectrometry Data Hypothesis Generation Scientific Discovery Collaborative AI Astrobiology
With upcoming sample return missions across the solar system and the increasing availability of mass spectrometry data, there is an urgent need for methods that analyze such data within the context of existing astrobiology literature and generate plausible hypotheses regarding the emergence of life on Earth. Hypothesis generation from mass spectrometry data is challenging due to factors such as environmental contaminants, the complexity of spectral peaks, and difficulties in cross-matching these peaks with prior studies. To address these challenges, we introduce AstroAgents, a large language model-based, multi-agent AI system for hypothesis generation from mass spectrometry data. AstroAgents is structured around eight collaborative agents: a data analyst, a planner, three domain scientists, an accumulator, a literature reviewer, and a critic. The system processes mass spectrometry data alongside user-provided research papers. The data analyst interprets the data, and the planner delegates specific segments to the scientist agents for in-depth exploration. The accumulator then collects and deduplicates the generated hypotheses, and the literature reviewer identifies relevant literature using Semantic Scholar. Finally, the critic evaluates the hypotheses, offering rigorous suggestions for improvement. To assess AstroAgents, an astrobiology expert evaluated the novelty and validity of more than a hundred hypotheses generated from data obtained from eight meteorites and ten soil samples. Of these hypotheses, surprisingly, 36% were identified as plausible, and among those, 66% were novel.
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Integrating Kernel Methods and Deep Neural Networks for Solving PDEs
Partial Differential Equations Physics-informed Machine Learning Neural Networks Kernel Methods Gaussian Processes
Physics-informed machine learning (PIML) has emerged as a promising alternative to conventional numerical methods for solving partial differential equations (PDEs).
PIML models are increasingly built via deep neural networks (NNs) whose performance is very sensitive to the NN's architecture, training settings, and loss function.
Motivated by this limitation, we introduce kernel-weighted Corrective Residuals (CoRes) to integrate the strengths of kernel methods and deep NNs for solving nonlinear PDE systems. To achieve this integration, we design a modular and robust framework which consistently outperforms competing methods in a broad range of benchmark problems. This performance improvement has a theoretical justification and is particularly attractive since we simplify the training process while negligibly increasing the inference costs.
Our studies also indicate that the proposed approach considerably decreases the sensitivity of NNs to factors such as random initialization, architecture type, and choice of optimizer.
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Learning Automata from Demonstrations, Examples, and Natural Language
Neurosymbolic Artificial Intelligence Multimodal Learning Learning Automata Learning from Demonstrations Deterministic Finite Automata (DFA) Large Language Models (LLMs) Formal Task Specification
Expert demonstrations have proven an easy way to indirectly specify complex tasks. Recent algorithms even support extracting unambiguous formal specifications, e.g. deterministic finite automata (DFA), from demonstrations. Unfortunately, these techniques are generally not sample-efficient. In this work, we introduce $L^\star LM$, an algorithm for learning DFAs from both demonstrations \emph{and} natural language. Due to the expressivity of natural language, we observe a significant improvement in the data efficiency of learning DFAs from expert demonstrations. Technically, $L^\star LM$ leverages large language models to answer membership queries about the underlying task. This is then combined with recent techniques for transforming learning from demonstrations into a sequence of labeled example learning problems. In our experiments, we observe the two modalities complement each other, yielding a powerful few-shot learner.
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Neural Langevin-type Stochastic Differential Equations for Astronomical time series Classification under Irregular Observations
Astronomical time series classification Neural Stochastic Differential Equations Langevin SDE
Addressing the classification challenges of irregular time series data in astronomical studies like Large Synoptic Survey Telescope (LSST), this research leverages Neural Stochastic Differential Equations (Neural SDEs) to tackle data irregularity and incompleteness. We analyze a comprehensive analysis to the Neural Langevin-type SDEs' optimal initial condition, which is pivotal role in modelling continuous latent state. Three different strategies for selecting initial condition are compared under regular and irregular scenario using LSST dataset. Our empirical evaluation using Langevin-type SDEs highlights the superiority of static approach over dynamic approaches for initial condition. This discovery highlights the effectiveness of well-chosen initial values of Neural SDEs to enhance the performance of astronomical time series classification under irregular observations.
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On the Effect of Consensus in Decentralized Deep Learning
decentralized deep learning performance effect consensus training models generalization gap consensus distance deep learning models learning
Decentralized training of deep learning models enables on-device learning over networks, as well as efficient scaling to large compute clusters. Experiments in earlier works revealed that decentralized training often suffers from generalization issues: the performance of models trained in a decentralized fashion is in general worse than the performance of models trained in a centralized fashion, and this generalization gap is impacted by parameters such as network size, communication topology, and data partitioning.
We identify the changing consensus distance between devices as a key parameter to explain the gap between centralized and decentralized training. We show that when the consensus distance does not grow too large, the performance of centralized training can be reached and sometimes surpassed. We highlight the intimate interplay between network topology and learning rate at the different training phases and discuss the implications for communication efficient training schemes. Our insights into the generalization gap in decentralized deep learning allow the principled design of better training schemes that mitigate these effects.
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Meta-Learning for Semi-Supervised Few-Shot Classification
Few-shot learning semi-supervised learning meta-learning
In few-shot classification, we are interested in learning algorithms that train a classifier from only a handful of labeled examples. Recent progress in few-shot classification has featured meta-learning, in which a parameterized model for a learning algorithm is defined and trained on episodes representing different classification problems, each with a small labeled training set and its corresponding test set. In this work, we advance this few-shot classification paradigm towards a scenario where unlabeled examples are also available within each episode. We consider two situations: one where all unlabeled examples are assumed to belong to the same set of classes as the labeled examples of the episode, as well as the more challenging situation where examples from other distractor classes are also provided. To address this paradigm, we propose novel extensions of Prototypical Networks (Snell et al., 2017) that are augmented with the ability to use unlabeled examples when producing prototypes. These models are trained in an end-to-end way on episodes, to learn to leverage the unlabeled examples successfully. We evaluate these methods on versions of the Omniglot and miniImageNet benchmarks, adapted to this new framework augmented with unlabeled examples. We also propose a new split of ImageNet, consisting of a large set of classes, with a hierarchical structure. Our experiments confirm that our Prototypical Networks can learn to improve their predictions due to unlabeled examples, much like a semi-supervised algorithm would.
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Unsupervised Active Pre-Training for Reinforcement Learning
Reinforcement Learning Unsupervised Learning Entropy Maximization Contrastive Learning Self-supervised Learning Exploration
We introduce a new unsupervised pre-training method for reinforcement learning called $\textbf{APT}$, which stands for $\textbf{A}\text{ctive}\textbf{P}\text{re-}\textbf{T}\text{raining}$. APT learns a representation and a policy initialization by actively searching for novel states in reward-free environments. We use the contrastive learning framework for learning the representation from collected transitions. The key novel idea is to collect data during pre-training by maximizing a particle based entropy computed in the learned latent representation space. By doing particle based entropy maximization, we alleviate the need for challenging density modeling and are thus able to scale our approach to image observations. APT successfully learns meaningful representations as well as policy initializations without using any reward. We empirically evaluate APT on the Atari game suite and DMControl suite by exposing task-specific reward to agent after a long unsupervised pre-training phase. On Atari games, APT achieves human-level performance on $12$ games and obtains highly competitive performance compared to canonical fully supervised RL algorithms. On DMControl suite, APT beats all baselines in terms of asymptotic performance and data efficiency and dramatically improves performance on tasks that are extremely difficult for training from scratch. Importantly, the pre-trained models can be fine-tuned to solve different tasks as long as the environment does not change. Finally, we also pre-train multi-environment encoders on data from multiple environments and show generalization to a broad set of RL tasks.
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Smooth Activations and Reproducibility in Deep Networks
Deep networks activation functions reproducibility
Deep networks are gradually penetrating almost every domain in our lives due to their amazing success. However, with substantive performance accuracy improvements comes the price of irreproducibility. Two identical models, trained on the exact same training dataset may exhibit large differences in predictions on individual examples even when average accuracy is similar, especially when trained on highly distributed parallel systems. The popular Rectified Linear Unit (ReLU) activation has been key to recent success of deep networks. We demonstrate, however, that ReLU is also a catalyzer to irreproducibility in deep networks. We show that not only can activations smoother than ReLU provide better accuracy, but they can also provide better accuracy-reproducibility tradeoffs. We propose a new family of activations; Smooth ReLU (SmeLU), designed to give such better tradeoffs, while also keeping the mathematical expression simple, and thus implementation cheap. SmeLU is monotonic, mimics ReLU, while providing continuous gradients, yielding better reproducibility. We generalize SmeLU to give even more flexibility and then demonstrate that SmeLU and its generalized form are special cases of a more general methodology of REctified Smooth Continuous Unit (RESCU) activations.
Empirical results demonstrate the superior accuracy-reproducibility tradeoffs with smooth activations, SmeLU in particular.
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Provable Memorization via Deep Neural Networks using Sub-linear Parameters
memorization
It is known that $\Theta(N)$ parameters are sufficient for neural networks to memorize arbitrary $N$ input-label pairs. By exploiting depth, we show that $\Theta(N^{2/3})$ parameters suffice to memorize $N$ pairs, under a mild condition on the separation of input points. In particular, deeper networks (even with width $3$) are shown to memorize more pairs than shallow networks, which also agrees with the recent line of works on the benefits of depth for function approximation. We also provide empirical results that support our theoretical findings.
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EpidemiOptim: A Toolbox for the Optimization of Control Policies in Epidemiological Models
epidemiology covid19 reinforcement learning evolutionary algorithms multi-objective optimization decision-making toolbox
Epidemiologists model the dynamics of epidemics in order to propose control strategies based on pharmaceutical and non-pharmaceutical interventions (contact limitation, lock down, vaccination, etc). Hand-designing such strategies is not trivial because of the number of possible interventions and the difficulty to predict long-term effects. This task can be cast as an optimization problem where state-of-the-art machine learning algorithms such as deep reinforcement learning might bring significant value. However, the specificity of each domain - epidemic modelling or solving optimization problems - requires strong collaborations between researchers from different fields of expertise.
This is why we introduce EpidemiOptim, a Python toolbox that facilitates collaborations between researchers in epidemiology and optimization. EpidemiOptim turns epidemiological models and cost functions into optimization problems via a standard interface commonly used by optimization practitioners (OpenAI Gym). Reinforcement learning algorithms based on Q-Learning with deep neural networks (DQN) and evolutionary algorithms (NSGA-II) are already implemented. We illustrate the use of EpidemiOptim to find optimal policies for dynamical on-off lock-down control under the optimization of death toll and economic recess using a Susceptible-Exposed-Infectious-Removed (SEIR) model for SARS-CoV-2/COVID-19.
Using EpidemiOptim and its interactive visualization platform in Jupyter notebooks, epidemiologists, optimization practitioners and others (e.g. economists) can easily compare epidemiological models, costs functions and optimization algorithms to address important choices to be made by health decision-makers.
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FMix: Enhancing Mixed Sample Data Augmentation
msda cutmix models fmix mixup attention recent years many successful variants
Mixed Sample Data Augmentation (MSDA) has received increasing attention in recent years, with many successful variants such as MixUp and CutMix. We analyse MSDA from an information theoretic perspective, characterising learned models in terms of how they impact the models’ perception of the data. Ultimately, our analyses allow us to decouple two complementary properties of augmentations that are useful for reasoning about MSDA. From insight on the efficacy of CutMix in particular, we subsequently propose FMix, an MSDA that uses binary masks obtained by applying a threshold to low frequency images sampled from Fourier space. FMix improves performance over MixUp and CutMix for a number of models across a range of data sets and problem settings, obtaining new state-of-the-art results on CIFAR-10 and Fashion-MNIST.
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Individually Fair Rankings
algorithmic fairness learning to rank optimal transport
We develop an algorithm to train individually fair learning-to-rank (LTR) models. The proposed approach ensures items from minority groups appear alongside similar items from majority groups. This notion of fair ranking is based on the definition of individual fairness from supervised learning and is more nuanced than prior fair LTR approaches that simply ensure the ranking model provides underrepresented items with a basic level of exposure. The crux of our method is an optimal transport-based regularizer that enforces individual fairness and an efficient algorithm for optimizing the regularizer. We show that our approach leads to certifiably individually fair LTR models and demonstrate the efficacy of our method on ranking tasks subject to demographic biases.
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Benchmarks for Deep Off-Policy Evaluation
reinforcement learning off-policy evaluation benchmarks
Off-policy evaluation (OPE) holds the promise of being able to leverage large, offline datasets for both evaluating and selecting complex policies for decision making. The ability to learn offline is particularly important in many real-world domains, such as in healthcare, recommender systems, or robotics, where online data collection is an expensive and potentially dangerous process. Being able to accurately evaluate and select high-performing policies without requiring online interaction could yield significant benefits in safety, time, and cost for these applications. While many OPE methods have been proposed in recent years, comparing results between papers is difficult because currently there is a lack of a comprehensive and unified benchmark, and measuring algorithmic progress has been challenging due to the lack of difficult evaluation tasks. In order to address this gap, we present a collection of policies that in conjunction with existing offline datasets can be used for benchmarking off-policy evaluation. Our tasks include a range of challenging high-dimensional continuous control problems, with wide selections of datasets and policies for performing policy selection. The goal of our benchmark is to provide a standardized measure of progress that is motivated from a set of principles designed to challenge and test the limits of existing OPE methods. We perform an evaluation of state-of-the-art algorithms and provide open-source access to our data and code to foster future research in this area.
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Spider 2.0: Evaluating Language Models on Real-World Enterprise Text-to-SQL Workflows
LLM Benchmark Data Science and Engineering Code Generation Text-to-SQL LLM Agent
Real-world enterprise text-to-SQL workflows often involve complex cloud or local data across various database systems, multiple SQL queries in various dialects, and diverse operations from data transformation to analytics.
We introduce Spider 2.0, an evaluation framework comprising $632$ real-world text-to-SQL workflow problems derived from enterprise-level database use cases.
The databases in Spider 2.0 are sourced from real data applications, often containing over 1,000 columns and stored in local or cloud database systems such as BigQuery and Snowflake.
We show that solving problems in Spider 2.0 frequently requires understanding and searching through database metadata, dialect documentation, and even project-level codebases.
This challenge calls for models to interact with complex SQL workflow environments, process extremely long contexts, perform intricate reasoning, and generate multiple SQL queries with diverse operations, often exceeding $100$ lines, which goes far beyond traditional text-to-SQL challenges.
Our evaluations indicate that based on o1-preview, our code agent framework successfully solves only 21.3\% of the tasks, compared with 91.2\% on Spider 1.0 and 73.0\% on BIRD.
Our results on Spider 2.0 show that while language models have demonstrated remarkable performance in code generation --- especially in prior text-to-SQL benchmarks --- they require significant improvement in order to achieve adequate performance for real-world enterprise usage.
Progress on Spider 2.0 represents crucial steps towards developing intelligent, autonomous, code agents for real-world enterprise settings.
Our code, baseline models, and data are available at [spider2-sql.github.io](spider2-sql.github.io) .
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Succinct Network Channel and Spatial Pruning via Discrete Variable QCQP
Network Pruning Channel pruning Spatial pruning Network Compression MIQCQP Specified target resource constraint
Reducing the heavy computational cost of large convolutional neural networks is crucial when deploying the networks to resource-constrained environments. In this context, recent works propose channel pruning via greedy channel selection to achieve practical acceleration and memory footprint reduction. We first show this channel-wise approach ignores the inherent quadratic coupling between channels in the neighboring layers and cannot safely remove inactive weights during the pruning procedure. Furthermore, we show that these pruning methods cannot guarantee the given resource constraints are satisfied and cause discrepancy with the true objective. To this end, we formulate a principled optimization framework with discrete variable QCQP, which provably prevents any inactive weights and enables the exact guarantee of meeting the resource constraints in terms of FLOPs and memory. Also, we extend the pruning granularity beyond channels and jointly prune individual 2D convolution filters spatially for greater efficiency. Our experiments show competitive pruning results under the target resource constraints on CIFAR-10 and ImageNet datasets on various network architectures.
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PixelNN: Example-based Image Synthesis
conditional image synthesis nearest neighbors
We present a simple nearest-neighbor (NN) approach that synthesizes high-frequency photorealistic images from an ``incomplete'' signal such as a low-resolution image, a surface normal map, or edges. Current state-of-the-art deep generative models designed for such conditional image synthesis lack two important things: (1) they are unable to generate a large set of diverse outputs, due to the mode collapse problem. (2) they are not interpretable, making it difficult to control the synthesized output. We demonstrate that NN approaches potentially address such limitations, but suffer in accuracy on small datasets. We design a simple pipeline that combines the best of both worlds: the first stage uses a convolutional neural network (CNN) to map the input to a (overly-smoothed) image, and the second stage uses a pixel-wise nearest neighbor method to map the smoothed output to multiple high-quality, high-frequency outputs in a controllable manner. Importantly, pixel-wise matching allows our method to compose novel high-frequency content by cutting-and-pasting pixels from different training exemplars. We demonstrate our approach for various input modalities, and for various domains ranging from human faces, pets, shoes, and handbags.
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SOSELETO: A Unified Approach to Transfer Learning and Training with Noisy Labels
transfer learning
We present SOSELETO (SOurce SELEction for Target Optimization), a new method for exploiting a source dataset to solve a classification problem on a target dataset. SOSELETO is based on the following simple intuition: some source examples are more informative than others for the target problem. To capture this intuition, source samples are each given weights; these weights are solved for jointly with the source and target classification problems via a bilevel optimization scheme. The target therefore gets to choose the source samples which are most informative for its own classification task. Furthermore, the bilevel nature of the optimization acts as a kind of regularization on the target, mitigating overfitting. SOSELETO may be applied to both classic transfer learning, as well as the problem of training on datasets with noisy labels; we show state of the art results on both of these problems.
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Learned Belief Search: Efficiently Improving Policies in Partially Observable Settings
Search partially observable games multi-agent learning Hanabi
Search is an important tool for computing effective policies in single- and multi-agent environments, and has been crucial for achieving superhuman performance in several benchmark fully and partially observable games. However, one major limitation of prior search approaches for partially observable environments is that the computational cost scales poorly with the amount of hidden information. In this paper we present Learned Belief Search (LBS), a computationally efficient search procedure for partially observable environments. Rather than maintaining an exact belief distribution, LBS uses an approximate auto-regressive counterfactual belief that is learned as a supervised task. In multi-agent settings, LBS uses a novel public-private model architecture for underlying policies in order to efficiently evaluate these policies during rollouts. In the benchmark domain of Hanabi, LBS obtains more than 60% of the benefit of exact search while reducing compute requirements by 35×, allowing it to scale to larger settings that were inaccessible to previous search methods.
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Diffusion Models Using a Single Equation
generative modeling denoising diffusion DDIM DDPM
In this work I present a novel viewpoint and a simplistic implementation and explanation of denoising diffusion models, and also the intuition that we force these models to sample from the data distribution by misleading them. The aim of this blogpost is to lower the barrier of entry to the field of diffusion models, by providing an explanation of their inner workings that is mathematically very light (only uses a single equation, with carefully meaningfully named variables), and try to understand them from a different point of view compared to previous work. I also discuss new intuitions about these models, and provide an end-to-end, simple to use implementation for diffusion models, that is easy to customize and is intended be a good starting point for future projects on this subject.
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Learning Binary Trees via Sparse Relaxation
optimization binary trees
One of the most classical problems in machine learning is how to learn binary trees that split data into meaningful partitions. From classification/regression via decision trees to hierarchical clustering, binary trees are useful because they (a) are often easy to visualize; (b) make computationally-efficient predictions; and (c) allow for flexible partitioning. Because of this there has been extensive research on how to learn such trees. Optimization generally falls into one of three categories: 1. greedy node-by-node optimization; 2. probabilistic relaxations for differentiability; 3. mixed-integer programming (MIP). Each of these have downsides: greedy can myopically choose poor splits, probabilistic relaxations do not have principled ways to prune trees, MIP methods can be slow on large problems and may not generalize. In this work we derive a novel sparse relaxation for binary tree learning. By sparsely relaxing a new MIP, our approach is able to learn tree splits and tree pruning using state-of-the-art gradient-based approaches. We demonstrate how our approach is easily visualizable, is efficient, and is competitive with current work in classification/regression and hierarchical clustering.
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Zero-Shot Recommender Systems
Zero Shot Learning Bayesian Recommender Systems Deep Generative Models Neural Networks
Performance of recommender systems (RecSys) relies heavily on the amount of training data available. This poses a chicken-and-egg problem for early-stage products, whose amount of data, in turn, relies on the performance of their RecSys. In this paper, we explore the possibility of zero-shot learning in RecSys, to enable generalization from an old dataset to an entirely new dataset. We develop, to the best of our knowledge, the first deep generative model, dubbed ZEro-Shot Recommenders (ZESRec), that is trained on an old dataset and generalize to a new one where there areneither overlapping users nor overlapping items, a setting that contrasts typical cross-domain RecSys that has either overlapping users or items. We study three pairs of real-world datasets and demonstrate that ZESRec can successfully enable such zero-shot recommendations, opening up new opportunities for resolving the chicken-and-egg problem for data-scarce startups or early-stage products.
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Adaptive Cross-Modal Few-Shot Learning
few-shot learning cross-modality
Metric-based meta-learning techniques have successfully been applied to few-shot classification problems. However, leveraging cross-modal information in a few-shot setting has yet to be explored. When the support from visual information is limited in few-shot image classification, semantic representations (learned from unsupervised text corpora) can provide strong prior knowledge and context to help learning. Based on this intuition, we design a model that is able to leverage visual and semantic features in the context of few-shot classification. We propose an adaptive mechanism that is able to effectively combine both modalities conditioned on categories. Through a series of experiments, we show that our method boosts the performance of metric-based approaches by effectively exploiting language structure. Using this extra modality, our model bypass current unimodal state-of-the-art methods by a large margin on miniImageNet. The improvement in performance is particularly large when the number of shots are small.
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The impacts of known and unknown demonstrator irrationality on reward inference
irrationality reward learning irl
Algorithms inferring rewards from human behavior typically assume that people are (approximately) rational. In reality, people exhibit a wide array of irrationalities. Motivated by understanding the benefits of modeling these irrationalities, we analyze the effects that demonstrator irrationality has on reward inference. We propose operationalizing several forms of irrationality in the language of MDPs, by altering the Bellman optimality equation, and use this framework to study how these alterations affect inference.
We find that incorrectly assuming noisy-rationality for an irrational demonstrator can lead to remarkably poor reward inference accuracy, even in situations where inference with the correct model leads to good inference. This suggests a need to either model irrationalities or find reward inference algorithms that are more robust to misspecification of the demonstrator model. Surprisingly, we find that if we give the learner access to the correct model of the demonstrator's irrationality, these irrationalities can actually help reward inference. In other words, if we could choose between a world where humans were perfectly rational and the current world where humans have systematic biases, the current world might counter-intuitively be preferable for reward inference. We reproduce this effect in several domains. While this finding is mainly conceptual, it is perhaps actionable as well: we might ask human demonstrators for myopic demonstrations instead of optimal ones, as they are more informative for the learner and might be easier for a human to generate.
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Fast 3D Acoustic Scattering via Discrete Laplacian Based Implicit Function Encoders
wave equation wave acoustics geometric deep learning sound simulation shape laplacian
Acoustic properties of objects corresponding to scattering characteristics are frequently used for 3D audio content creation, environmental acoustic effects, localization and acoustic scene analysis, etc. The numeric solvers used to compute these acoustic properties are too slow for interactive applications. We present a novel geometric deep learning algorithm based on discrete-laplacian and implicit encoders to compute these characteristics for rigid or deformable objects at interactive rates. We use a point cloud approximation of each object, and each point is encoded in a high-dimensional latent space. Our multi-layer network can accurately estimate these acoustic properties for arbitrary topologies and takes less than 1ms per object on a NVIDIA GeForce RTX 2080 Ti GPU. We also prove that our learning method is permutation and rotation invariant and demonstrate high accuracy on objects that are quite different from the training data. We highlight its application to generating environmental acoustic effects in dynamic environments.
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Predicting the impact of dataset composition on model performance
Experimental design generalization data collection
Real-world machine learning systems are often are trained using a mix of data sources with varying cost and quality. Understanding how the size and composition of a training dataset affect model performance is critical for advancing our understanding of generalization, as well as designing more effective data collection policies. We show that there is a simple, accurate way to predict the loss incurred by a model based on data size and composition. Our work expands recent observations of log-linear generalization error and uses this to cast model performance prediction as a learning problem. Using the theory of optimal experimental design, we derive a simple rational function approximation to generalization error that can be fitted using a few model training runs. Our approach achieves nearly exact ($r^2>.93$) predictions of model performance under substantial extrapolation in two different standard supervised learning tasks and is accurate ($r^2 > .83$) on more challenging machine translation and question answering tasks where baselines achieve worse-than-random performance.
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Three Dimensional Reconstruction of Botanical Trees with Simulatable Geometry
botanical trees dimensional reconstruction simulatable geometry step pipeline challenging problem full accurate dimensional reconstructions topological
We tackle the challenging problem of creating full and accurate three dimensional reconstructions of botanical trees with the topological and geometric accuracy required for subsequent physical simulation, e.g. in response to wind forces. Although certain aspects of our approach would benefit from various improvements, our results exceed the state of the art especially in geometric and topological complexity and accuracy. Starting with two dimensional RGB image data acquired from cameras attached to drones, we create point clouds, textured triangle meshes, and a simulatable and skinned cylindrical articulated rigid body model. We discuss the pros and cons of each step of our pipeline, and in order to stimulate future research we make the raw and processed data from every step of the pipeline as well as the final geometric reconstructions publicly available.
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Learning Two-Step Hybrid Policy for Graph-Based Interpretable Reinforcement Learning
Graph-based Reinforcement Learning Interpretable Reinforcement Learning Generalization Robustness
We present a two-step hybrid reinforcement learning (RL) policy that is designed to generate interpretable and robust hierarchical policies
on the RL problem with graph-based input. Unlike prior deep reinforcement learning policies parameterized by an end-to-end black-box graph neural network, our approach disentangles the decision-making process into two steps. The first step is a simplified classification problem that maps the graph input to an action group where all actions share a similar semantic meaning. The second step implements a sophisticated rule-miner that conducts explicit one-hop reasoning over the graph and identifies decisive edges in the graph input without the necessity of heavy domain knowledge. This two-step hybrid policy presents human-friendly interpretations and achieves better performance in terms of generalization and robustness. Extensive experimental studies on four levels of complex text-based games have demonstrated the superiority of the proposed method compared to the state-of-the-art.
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Stochastic Activation Pruning for Robust Adversarial Defense
adversarial examples mixed strategy sap stochastic activation vulnerable perturbations real images imperceptible
Neural networks are known to be vulnerable to adversarial examples. Carefully chosen perturbations to real images, while imperceptible to humans, induce misclassification and threaten the reliability of deep learning systems in the wild. To guard against adversarial examples, we take inspiration from game theory and cast the problem as a minimax zero-sum game between the adversary and the model. In general, for such games, the optimal strategy for both players requires a stochastic policy, also known as a mixed strategy. In this light, we propose Stochastic Activation Pruning (SAP), a mixed strategy for adversarial defense. SAP prunes a random subset of activations (preferentially pruning those with smaller magnitude) and scales up the survivors to compensate. We can apply SAP to pretrained networks, including adversarially trained models, without fine-tuning, providing robustness against adversarial examples. Experiments demonstrate that SAP confers robustness against attacks, increasing accuracy and preserving calibration.
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Anti-Distillation: Improving Reproducibility of Deep Networks
Deep networks ensembles reproducibility
Deep networks have been revolutionary in improving performance of machine learning and artificial intelligence systems.
Their high prediction accuracy, however, comes at a price of model irreproducibility in very high levels that do not occur with classical linear models. Two models, even if they are supposedly identical, with identical architecture and identical trained parameter sets, and that are trained on the same set of training examples, while possibly providing identical average prediction accuracies, may predict very differently on individual, previously unseen, examples. Prediction differences may be as large as the order of magnitude of the predictions themselves. Ensembles have been shown to somewhat mitigate this behavior, but without an extra push, may not be utilizing their full potential. In this work, a novel approach, Anti-Distillation, is proposed to address irreproducibility in deep networks, where ensemble models are used to generate predictions. Anti-Distillation forces ensemble components away from one another by techniques like de-correlating their outputs over mini-batches of examples, forcing them to become even more different and more diverse. Doing so enhances the benefit of ensembles, making the final predictions more reproducible. Empirical results demonstrate substantial prediction difference reductions achieved by Anti-Distillation on benchmark and real datasets.
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Evaluating Text Humanlikeness via Self-Similarity Exponent
humanlikeness self-similarity exponent fractal structure of language
Evaluating text generation quality in large language models (LLMs) is critical for their deployment. We investigate the self-similarity exponent S, a fractal-based metric, as a metric for quantifying "humanlikeness." Using texts from the public available dataset and Qwen models (with/without instruction tuning), we find human-written texts exhibit S = 0.57, while non-instruct models show higher values, and instruct-tuned models approach human-like patterns. Larger models improve quality but benefit more with instruction tuning. Our findings suggest S as an effective metric for assessing LLM performance.
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Shape or Texture: Understanding Discriminative Features in CNNs
Shape Texture Shape Bias Texture Bias Shape Encoding Mutual Information
Contrasting the previous evidence that neurons in the later layers of a Convolutional Neural Network (CNN) respond to complex object shapes, recent studies have shown that CNNs actually exhibit a 'texture bias': given an image with both texture and shape cues (e.g., a stylized image), a CNN is biased towards predicting the category corresponding to the texture. However, these previous studies conduct experiments on the final classification output of the network, and fail to robustly evaluate the bias contained (i) in the latent representations, and (ii) on a per-pixel level. In this paper, we design a series of experiments that overcome these issues. We do this with the goal of better understanding what type of shape information contained in the network is discriminative, where shape information is encoded, as well as when the network learns about object shape during training. We show that a network learns the majority of overall shape information at the first few epochs of training and that this information is largely encoded in the last few layers of a CNN. Finally, we show that the encoding of shape does not imply the encoding of localized per-pixel semantic information. The experimental results and findings provide a more accurate understanding of the behaviour of current CNNs, thus helping to inform future design choices.
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Distributionally Robust Learning for Unsupervised Domain Adaptation
Distributionally Robust Learning Domain Adaptation Self-training Density Ratio Estimation
We propose a distributionally robust learning (DRL) method for unsupervised domain adaptation (UDA) that scales to modern computer-vision benchmarks. DRL can be naturally formulated as a competitive two-player game between a predictor and an adversary that is allowed to corrupt the labels, subject to certain constraints, and reduces to incorporating a density ratio between the source and target domains (under the standard log loss). This formulation motivates the use of two neural networks that are jointly trained --- a discriminative network between the source and target domains for density-ratio estimation, in addition to the standard classification network. The use of a density ratio in DRL prevents the model from being overconfident on target inputs far away from the source domain. Thus, DRL provides conservative confidence estimation in the target domain, even when the target labels are not available. This conservatism motivates the use of DRL in self-training for sample selection, and we term the approach distributionally robust self-training (DRST). In our experiments, DRST generates more calibrated probabilities and achieves state-of-the-art self-training accuracy on benchmark datasets. We demonstrate that DRST captures shape features more effectively, and reduces the extent of distributional shift during self-training.
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Prior Knowledge Representation for Self-Attention Networks
Prior Knowledge Universal Representation Self-Attention Networks Neural Machine Translation
Self-attention networks (SANs) have shown promising empirical results in various natural language processing tasks. Typically, it gradually learning language knowledge on the whole training dataset in parallel and stacked ways, thereby modeling language representation. In this paper, we propose a simple and general representation method to consider prior knowledge related to language representation from the beginning of training. Also, the proposed method allows SANs to leverage prior knowledge in a universal way compatible with neural networks. Furthermore, we apply it to one prior word frequency knowledge for the monolingual data and other prior translation lexicon knowledge for the bilingual data, respectively, thereby enhancing the language representation. Experimental results on WMT14 English-to-German and WMT17 Chinese-to-English translation tasks demonstrate the effectiveness and universality of the proposed method over a strong Transformer-based baseline.
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Tailoring: encoding inductive biases by optimizing unsupervised objectives at prediction time
inductive biases meta-learning semi-supervised learning adversarial learning representation learning transductive learning
From CNNs to attention mechanisms, encoding inductive biases into neural networks has been a fruitful source of improvement in machine learning. Auxiliary losses are a general way of encoding biases in order to help networks learn better representations by adding extra terms to the loss function. However, since they are minimized on the training data, they suffer from the same generalization gap as regular task losses. Moreover, by changing the loss function, the network is optimizing a different objective than the one we care about. In this work we solve both problems: first, we take inspiration from transductive learning and note that, after receiving an input but before making a prediction, we can fine-tune our models on any unsupervised objective. We call this process tailoring, because we customize the model to each input. Second, we formulate a nested optimization (similar to those in meta-learning) and train our models to perform well on the task loss after adapting to the tailoring loss. The advantages of tailoring and meta-tailoring are discussed theoretically and demonstrated empirically on several diverse examples: encoding inductive conservation laws from physics to improve predictions, improving local smoothness to increase robustness to adversarial examples, and using contrastive losses on the query image to improve generalization.
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A Coach-Player Framework for Dynamic Team Composition
Multiagent reinforcement learning
In real-world multi-agent teams, agents with different capabilities may join or leave "on the fly" without altering the team's overarching goals. Coordinating teams with such dynamic composition remains a challenging problem: the optimal team strategy may vary with its composition. Inspired by real-world team sports, we propose a coach-player framework to tackle this problem. We assume that the players only have a partial view of the environment, while the coach has a complete view. The coach coordinates the players by distributing individual strategies. Specifically, we 1) propose an attention mechanism for both the players and the coach; 2) incorporate a variational objective to regularize learning; and 3) design an adaptive communication method to let the coach decide when to communicate with different players. Our attention mechanism on the players and the coach allows for a varying number of heterogeneous agents, and can thus tackle the dynamic team composition. We validate our methods on resource collection tasks in multi-agent particle environment. We demonstrate zero-shot generalization to new team compositions with varying numbers of heterogeneous agents. The performance of our method is comparable or even better than the setting where all players have a full view of the environment, but no coach. Moreover, we see that the performance stays nearly the same even when the coach communicates as little as 13% of the time using our adaptive communication strategy. These results demonstrate the significance of a coach to coordinate players in dynamic teams.
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Differentially Private Synthetic Data: Applied Evaluations and Enhancements
privacy differential privacy generative adversarial networks gan security synthetic data evaluation benchmarking ensemble
Machine learning practitioners frequently seek to leverage the most informative available data, without violating the data owner's privacy, when building predictive models. Differentially private data synthesis protects personal details from exposure, and allows for the training of differentially private machine learning models on privately generated datasets. But how can we effectively assess the efficacy of differentially private synthetic data? In this paper, we survey four differentially private generative adversarial networks for data synthesis. We evaluate each of them at scale on five standard tabular datasets, and in two applied industry scenarios. We benchmark with novel metrics from recent literature and other standard machine learning tools. Our results suggest some synthesizers are more applicable for different privacy budgets, and we further demonstrate complicating domain-based tradeoffs in selecting an approach. We offer experimental learning on applied machine learning scenarios with private internal data to researchers and practitioners alike. In addition, we propose QUAIL, a two model hybrid approach to generating synthetic data. We examine QUAIL's tradeoffs, and note circumstances in which it outperforms baseline differentially private supervised learning models under the same budget constraint.
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Unsupervised Representation Learning for Time Series with Temporal Neighborhood Coding
unsupervised representation time series framework distribution signals temporal neighborhood complex rich information
Time series are often complex and rich in information but sparsely labeled and therefore challenging to model. In this paper, we propose a self-supervised framework for learning robust and generalizable representations for time series. Our approach, called Temporal Neighborhood Coding (TNC), takes advantage of the local smoothness of a signal's generative process to define neighborhoods in time with stationary properties. Using a debiased contrastive objective, our framework learns time series representations by ensuring that in the encoding space, the distribution of signals from within a neighborhood is distinguishable from the distribution of non-neighboring signals. Our motivation stems from the medical field, where the ability to model the dynamic nature of time series data is especially valuable for identifying, tracking, and predicting the underlying patients' latent states in settings where labeling data is practically impossible. We compare our method to recently developed unsupervised representation learning approaches and demonstrate superior performance on clustering and classification tasks for multiple datasets.
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Client Selection in Federated Learning: Convergence Analysis and Power-of-Choice Selection Strategies
distributed optimization federated learning client selection
Federated learning is a distributed optimization paradigm that enables a large number of resource-limited client nodes to cooperatively train a model without data sharing. Several works have analyzed the convergence of federated learning by accounting of data heterogeneity, communication and computation limitations, and partial client participation. However, they assume unbiased client participation, where clients are selected at random or in proportion of their data sizes. In this paper, we present the first convergence analysis of federated optimization for biased client selection strategies, and quantify how the selection bias affects convergence speed. We reveal that biasing client selection towards clients with higher local loss achieves faster error convergence. Using this insight, we propose Power-of-Choice, a communication- and computation-efficient client selection framework that can flexibly span the trade-off between convergence speed and solution bias. We also propose an extension of Power-of-Choice that is able to maintain convergence speed improvement while diminishing the selection skew. Our experiments demonstrate that Power-of-Choice strategies converge up to 3 $\times$ faster and give $10$% higher test accuracy than the baseline random selection.
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Deep Ecological Inference
ecological inference representation learning multi-task learning bayesian deep learning
We introduce an efficient approximation to the loss function for the ecological inference problem, where individual labels are predicted from aggregates. This allows us to construct ecological versions of linear models, deep neural networks, and Bayesian neural networks. Using these models we infer probabilities of vote choice for candidates in the Maryland 2018 midterm elections for 2,322,277 voters in 2055 precincts. We show that increased network depth and joint learning of multiple races within an election improves the accuracy of ecological inference when compared to benchmark data from polling. Additionally we leverage data on the joint distribution of ballots (available from ballot images which are public for election administration purposes) to show that joint learning leads to significantly improved recovery of the covariance structure for multi-task ecological inference. Our approach also allows learning latent representations of voters, which we show outperform raw covariates for leave-one-out prediction.
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A Missing Testbed for LLM Pre-Training Membership Inference Attacks
Large Language Models Foundation Models Membership Inference Attacks Dataset Privacy Benchmark Trustworthy AI
We introduce a simple and rigorous testbed for membership inference attacks (MIA) against pre-training sequences for large language models (LLMs). Our testbed addresses the following gaps in existing evaluations, which lack: (1) \textit{uniform} sampling of member/non-member documents of varying lengths from pre-training shards; (2) large-scale \textit{deduplication} at varying strengths, both within and across the sampled members/non-members; and (3) rigorous \textit{statistical tests} to detect member/non-member distribution shifts that cause faulty evaluations and are otherwise imperceptible to the heuristic techniques used in prior work. We provide both global- and domain-level datasets (e.g., Reddit, Stack Exchange, Wikipedia), derived from fully-open pre-trained LLM/dataset pairs including Pythia/Pile, Olmo/Dolma, and our custom pre-trained GPT-2-Large on FineWeb-Edu. We additionally open source a modular and extensible codebase that facilitates the creation of custom, statistically validated, and deduplicated evaluation data using future open models and datasets. In sum, our work is a concrete step towards addressing the evaluation issues discussed by prior work.
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Monotonic Robust Policy Optimization with Model Discrepancy
Reinforcement Learning generalization
State-of-the-art deep reinforcement learning (DRL) algorithms tend to overfit in some specific environments due to the lack of data diversity in training. To mitigate the model discrepancy between training and target (testing) environments, domain randomization (DR) can generate plenty of environments with a sufficient diversity by randomly sampling environment parameters in simulator. Though standard DR using a uniform distribution improves the average performance on the whole range of environments, the worst-case environment is usually neglected without any performance guarantee. Since the average and worst-case performance are equally important for the generalization in RL, in this paper, we propose a policy optimization approach for concurrently improving the policy's performance in the average case (i.e., over all possible environments) and the worst-case environment. We theoretically derive a lower bound for the worst-case performance of a given policy over all environments. Guided by this lower bound, we formulate an optimization problem which aims to optimize the policy and sampling distribution together, such that the constrained expected performance of all environments is maximized. We prove that the worst-case performance is monotonically improved by iteratively solving this optimization problem. Based on the proposed lower bound, we develop a practical algorithm, named monotonic robust policy optimization (MRPO), and validate MRPO on several robot control tasks. By modifying the environment parameters in simulation, we obtain environments for the same task but with different transition dynamics for training and testing. We demonstrate that MRPO can improve both the average and worst-case performance in the training environments, and facilitate the learned policy with a better generalization capability in unseen testing environments.
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Entropy-SGD optimizes the prior of a PAC-Bayes bound: Data-dependent PAC-Bayes priors via differential privacy
generalization error neural networks statistical learning theory PAC-Bayes theory
We show that Entropy-SGD (Chaudhari et al., 2017), when viewed as a learning algorithm, optimizes a PAC-Bayes bound on the risk of a Gibbs (posterior) classifier, i.e., a randomized classifier obtained by a risk-sensitive perturbation of the weights of a learned classifier. Entropy-SGD works by optimizing the bound’s prior, violating the hypothesis of the PAC-Bayes theorem that the prior is chosen independently of the data. Indeed, available implementations of Entropy-SGD rapidly obtain zero training error on random labels and the same holds of the Gibbs posterior. In order to obtain a valid generalization bound, we show that an ε-differentially private prior yields a valid PAC-Bayes bound, a straightforward consequence of results connecting generalization with differential privacy. Using stochastic gradient Langevin dynamics (SGLD) to approximate the well-known exponential release mechanism, we observe that generalization error on MNIST (measured on held out data) falls within the (empirically nonvacuous) bounds computed under the assumption that SGLD produces perfect samples. In particular, Entropy-SGLD can be configured to yield relatively tight generalization bounds and still fit real labels, although these same settings do not obtain state-of-the-art performance.
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Graph Learning via Spectral Densification
Spectral Graph Theory Undirected Graphical models Gaussian Markov Random Fields
Graph learning plays important role in many data mining and machine learning tasks, such as manifold learning, data representation and analysis, dimensionality reduction, data clustering, and visualization, etc. For the first time, we present a highly-scalable spectral graph densification approach (GRASPEL) for graph learning from data. By limiting the precision matrix to be a graph-Laplacian-like matrix in graphical Lasso, our approach aims to learn ultra-sparse undirected graphs from potentially high-dimensional input data. A very unique property of the graphs learned by GRASPEL is that the spectral embedding (or approximate effective-resistance) distances on the graph will encode the similarities between the original input data points. By interleaving the latest high-performance nearly-linear
time spectral methods, ultrasparse yet spectrally-robust graphs can be learned by identifying and including the most spectrally-critical edges into the graph. Compared with prior state-of-the-art graph learning approaches, GRASPEL is more scalable and allows substantially improving computing efficiency and solution quality of a variety of data mining and
machine learning applications, such as manifold learning, spectral clustering (SC), and dimensionality reduction.
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Continuous-time neural networks for modeling linear dynamical systems
Continuous-time neural networks Neural Architecture Search (NAS) Ordinary Differential Equations (ODEs) error analysis
We propose to model Linear Time-Invariant (LTI) systems as a first step towards constructing sparse neural networks for modeling more complex dynamical systems. We use a variant of continuous-time neural networks in which the output of each neuron evolves continuously as a solution of a first or second-order Ordinary Differential Equation (ODE). Instead of computing the network parameters from data, we rely on system identification techniques to obtain a state-space model. Our algorithm is gradient-free, numerically stable, and computes a sparse architecture together with all network parameters from the given state-space matrices of the LTI system. We provide an upper bound on the numerical errors for our constructed neural networks and demonstrate their accuracy by simulating the transient convection-diffusion equation.
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Energy-based View of Retrosynthesis
Applications Retrosynthesis Energy-based Model
Retrosynthesis—the process of identifying a set of reactants to synthesize a target molecule—is of vital importance to material design and drug discovery. Existing machine learning approaches based on language models and graph neural networks have achieved encouraging results. However, the inner connections of these models are rarely discussed, and rigorous evaluations of these models are largely in need. In this paper, we propose a framework that unifies sequence- and graph-based methods as energy-based models (EBMs) with different energy functions. This unified point of view establishes connections between different models and identifies the differences between them, thereby promoting the understanding of model design. We also provide a comprehensive assessment of performance to the community. Moreover, we present a novel “dual” variant within the framework that performs consistent training over Bayesian forward- and backward-prediction by constraining the agreement between the two directions. This model improves the state of the art for template-free approaches where the reaction type is unknown and known.
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Structured Prediction using cGANs with Fusion Discriminator
Generative Adversarial Network GAN cGAN Structured Prediction Fusion.
We propose the fusion discriminator, a single unified framework for incorporating conditional information into a generative adversarial network (GAN) for a variety of distinct structured prediction tasks, including image synthesis, semantic segmentation, and depth estimation. Much like commonly used convolutional neural network - conditional Markov random field (CNN-CRF) models, the proposed method is able to enforce higher-order consistency in the model, but without being limited to a very specific class of potentials. The method is conceptually simple and flexible, and our experimental results demonstrate improvement on several diverse structured prediction tasks.
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