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"""
# Let's assume that if one batch start with `bos`, all batched also do
if input_ids[0, 0] == self.bos_token_id:
input_ids = input_ids[:, 1:]
if input_ids.shape[-1] - self.processor.context_width < 1:
raise ValueError(
f"Must have at least `1` token to score after the first "
f"min_prefix_len={self.processor.context_width} tokens required by the seeding scheme."
)
num_tokens_scored, green_token_count = self._score_ngrams_in_passage(input_ids)
z_score = self._compute_z_score(green_token_count, num_tokens_scored)
prediction = z_score > z_threshold
if return_dict:
p_value = self._compute_pval(z_score)
confidence = 1 - p_value
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return WatermarkDetectorOutput(
num_tokens_scored=num_tokens_scored,
num_green_tokens=green_token_count,
green_fraction=green_token_count / num_tokens_scored,
z_score=z_score,
p_value=p_value,
prediction=prediction,
confidence=confidence,
)
return prediction
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class BayesianDetectorConfig(PretrainedConfig):
"""
This is the configuration class to store the configuration of a [`BayesianDetectorModel`]. It is used to
instantiate a Bayesian Detector model according to the specified arguments.
Configuration objects inherit from [`PretrainedConfig`] and can be used to control the model outputs. Read the
documentation from [`PretrainedConfig`] for more information.
Args:
watermarking_depth (`int`, *optional*):
The number of tournament layers.
base_rate (`float1`, *optional*, defaults to 0.5):
Prior probability P(w) that a text is watermarked.
"""
def __init__(self, watermarking_depth: int = None, base_rate: float = 0.5, **kwargs):
self.watermarking_depth = watermarking_depth
self.base_rate = base_rate
# These can be set later to store information about this detector.
self.model_name = None
self.watermarking_config = None
super().__init__(**kwargs)
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def set_detector_information(self, model_name, watermarking_config):
self.model_name = model_name
self.watermarking_config = watermarking_config
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class BayesianWatermarkDetectorModelOutput(ModelOutput):
"""
Base class for outputs of models predicting if the text is watermarked.
Args:
loss (`torch.FloatTensor` of shape `(1,)`, *optional*, returned when `labels` is provided):
Language modeling loss.
posterior_probabilities (`torch.FloatTensor` of shape `(1,)`):
Multiple choice classification loss.
"""
loss: Optional[torch.FloatTensor] = None
posterior_probabilities: Optional[torch.FloatTensor] = None
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class BayesianDetectorWatermarkedLikelihood(nn.Module):
"""Watermarked likelihood model for binary-valued g-values.
This takes in g-values and returns p(g_values|watermarked).
"""
def __init__(self, watermarking_depth: int):
"""Initializes the model parameters."""
super().__init__()
self.watermarking_depth = watermarking_depth
self.beta = torch.nn.Parameter(-2.5 + 0.001 * torch.randn(1, 1, watermarking_depth))
self.delta = torch.nn.Parameter(0.001 * torch.randn(1, 1, self.watermarking_depth, watermarking_depth))
def _compute_latents(self, g_values: torch.Tensor) -> Tuple[torch.Tensor, torch.Tensor]:
"""Computes the unique token probability distribution given g-values.
Args:
g_values (`torch.Tensor` of shape `(batch_size, seq_len, watermarking_depth)`):
PRF values.
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Returns:
p_one_unique_token and p_two_unique_tokens, both of shape
[batch_size, seq_len, watermarking_depth]. p_one_unique_token[i,t,l]
gives the probability of there being one unique token in a tournament
match on layer l, on timestep t, for batch item i.
p_one_unique_token[i,t,l] + p_two_unique_token[i,t,l] = 1.
"""
# Tile g-values to produce feature vectors for predicting the latents
# for each layer in the tournament; our model for the latents psi is a
# logistic regression model psi = sigmoid(delta * x + beta).
# [batch_size, seq_len, watermarking_depth, watermarking_depth]
x = torch.repeat_interleave(torch.unsqueeze(g_values, dim=-2), self.watermarking_depth, axis=-2)
# mask all elements above -1 diagonal for autoregressive factorization
x = torch.tril(x, diagonal=-1)
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# [batch_size, seq_len, watermarking_depth]
# (i, j, k, l) x (i, j, k, l) -> (i, j, k) einsum equivalent
logits = (self.delta[..., None, :] @ x.type(self.delta.dtype)[..., None]).squeeze() + self.beta
p_two_unique_tokens = torch.sigmoid(logits)
p_one_unique_token = 1 - p_two_unique_tokens
return p_one_unique_token, p_two_unique_tokens
def forward(self, g_values: torch.Tensor) -> torch.Tensor:
"""Computes the likelihoods P(g_values|watermarked).
Args:
g_values (`torch.Tensor` of shape `(batch_size, seq_len, watermarking_depth)`):
g-values (values 0 or 1)
Returns:
p(g_values|watermarked) of shape [batch_size, seq_len, watermarking_depth].
"""
p_one_unique_token, p_two_unique_tokens = self._compute_latents(g_values)
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# P(g_tl | watermarked) is equal to
# 0.5 * [ (g_tl+0.5) * p_two_unique_tokens + p_one_unique_token].
return 0.5 * ((g_values + 0.5) * p_two_unique_tokens + p_one_unique_token)
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class BayesianDetectorModel(PreTrainedModel):
r"""
Bayesian classifier for watermark detection.
This detector uses Bayes' rule to compute a watermarking score, which is the sigmoid of the log of ratio of the
posterior probabilities P(watermarked|g_values) and P(unwatermarked|g_values). Please see the section on
BayesianScore in the paper for further details.
Paper URL: https://www.nature.com/articles/s41586-024-08025-4
Note that this detector only works with non-distortionary Tournament-based watermarking using the Bernoulli(0.5)
g-value distribution.
This model inherits from [`PreTrainedModel`]. Check the superclass documentation for the generic methods the
library implements for all its model (such as downloading or saving, resizing the input embeddings, pruning heads
etc.)
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This model is also a PyTorch [torch.nn.Module](https://pytorch.org/docs/stable/nn.html#torch.nn.Module) subclass.
Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage
and behavior.
Parameters:
config ([`BayesianDetectorConfig`]): Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the
configuration. Check out the [`~PreTrainedModel.from_pretrained`] method to load the model weights.
"""
config_class = BayesianDetectorConfig
base_model_prefix = "model"
def __init__(self, config):
super().__init__(config)
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self.watermarking_depth = config.watermarking_depth
self.base_rate = config.base_rate
self.likelihood_model_watermarked = BayesianDetectorWatermarkedLikelihood(
watermarking_depth=self.watermarking_depth
)
self.prior = torch.nn.Parameter(torch.tensor([self.base_rate]))
def _init_weights(self, module):
"""Initialize the weights."""
if isinstance(module, nn.Parameter):
module.weight.data.normal_(mean=0.0, std=0.02)
def _compute_posterior(
self,
likelihoods_watermarked: torch.Tensor,
likelihoods_unwatermarked: torch.Tensor,
mask: torch.Tensor,
prior: float,
) -> torch.Tensor:
"""
Compute posterior P(w|g) given likelihoods, mask and prior.
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Args:
likelihoods_watermarked (`torch.Tensor` of shape `(batch, length, depth)`):
Likelihoods P(g_values|watermarked) of g-values under watermarked model.
likelihoods_unwatermarked (`torch.Tensor` of shape `(batch, length, depth)`):
Likelihoods P(g_values|unwatermarked) of g-values under unwatermarked model.
mask (`torch.Tensor` of shape `(batch, length)`):
A binary array indicating which g-values should be used. g-values with mask value 0 are discarded.
prior (`float`):
the prior probability P(w) that the text is watermarked.
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Returns:
Posterior probability P(watermarked|g_values), shape [batch].
"""
mask = torch.unsqueeze(mask, dim=-1)
prior = torch.clamp(prior, min=1e-5, max=1 - 1e-5)
log_likelihoods_watermarked = torch.log(torch.clamp(likelihoods_watermarked, min=1e-30, max=float("inf")))
log_likelihoods_unwatermarked = torch.log(torch.clamp(likelihoods_unwatermarked, min=1e-30, max=float("inf")))
log_odds = log_likelihoods_watermarked - log_likelihoods_unwatermarked
# Sum relative surprisals (log odds) across all token positions and layers.
relative_surprisal_likelihood = torch.einsum("i...->i", log_odds * mask)
# Compute the relative surprisal prior
relative_surprisal_prior = torch.log(prior) - torch.log(1 - prior)
# Combine prior and likelihood.
# [batch_size]
relative_surprisal = relative_surprisal_prior + relative_surprisal_likelihood
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# Compute the posterior probability P(w|g) = sigmoid(relative_surprisal).
return torch.sigmoid(relative_surprisal)
def forward(
self,
g_values: torch.Tensor,
mask: torch.Tensor,
labels: Optional[torch.Tensor] = None,
loss_batch_weight=1,
return_dict=False,
) -> BayesianWatermarkDetectorModelOutput:
"""
Computes the watermarked posterior P(watermarked|g_values).
Args:
g_values (`torch.Tensor` of shape `(batch_size, seq_len, watermarking_depth, ...)`):
g-values (with values 0 or 1)
mask:
A binary array shape [batch_size, seq_len] indicating which g-values should be used. g-values with mask
value 0 are discarded.
Returns:
p(watermarked | g_values), of shape [batch_size].
"""
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likelihoods_watermarked = self.likelihood_model_watermarked(g_values)
likelihoods_unwatermarked = 0.5 * torch.ones_like(g_values)
out = self._compute_posterior(
likelihoods_watermarked=likelihoods_watermarked,
likelihoods_unwatermarked=likelihoods_unwatermarked,
mask=mask,
prior=self.prior,
)
loss = None
if labels is not None:
loss_fct = BCELoss()
loss_unwweight = torch.sum(self.likelihood_model_watermarked.delta**2)
loss_weight = loss_unwweight * loss_batch_weight
loss = loss_fct(torch.clamp(out, 1e-5, 1 - 1e-5), labels) + loss_weight
if not return_dict:
return (out,) if loss is None else (out, loss)
return BayesianWatermarkDetectorModelOutput(loss=loss, posterior_probabilities=out)
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class SynthIDTextWatermarkDetector:
r"""
SynthID text watermark detector class.
This class has to be initialized with the trained bayesian detector module check script
in examples/synthid_text/detector_training.py for example in training/saving/loading this
detector module. The folder also showcases example use case of this detector.
Parameters:
detector_module ([`BayesianDetectorModel`]):
Bayesian detector module object initialized with parameters.
Check examples/research_projects/synthid_text/detector_training.py for usage.
logits_processor (`SynthIDTextWatermarkLogitsProcessor`):
The logits processor used for watermarking.
tokenizer (`Any`):
The tokenizer used for the model.
Examples:
```python
>>> from transformers import (
... AutoTokenizer, BayesianDetectorModel, SynthIDTextWatermarkLogitsProcessor, SynthIDTextWatermarkDetector
... )
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>>> # Load the detector. See examples/research_projects/synthid_text for training a detector.
>>> detector_model = BayesianDetectorModel.from_pretrained("joaogante/dummy_synthid_detector")
>>> logits_processor = SynthIDTextWatermarkLogitsProcessor(
... **detector_model.config.watermarking_config, device="cpu"
... )
>>> tokenizer = AutoTokenizer.from_pretrained(detector_model.config.model_name)
>>> detector = SynthIDTextWatermarkDetector(detector_model, logits_processor, tokenizer)
>>> # Test whether a certain string is watermarked
>>> test_input = tokenizer(["This is a test input"], return_tensors="pt")
>>> is_watermarked = detector(test_input.input_ids)
```
"""
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def __init__(
self,
detector_module: BayesianDetectorModel,
logits_processor: SynthIDTextWatermarkLogitsProcessor,
tokenizer: Any,
):
self.detector_module = detector_module
self.logits_processor = logits_processor
self.tokenizer = tokenizer
def __call__(self, tokenized_outputs: torch.Tensor):
# eos mask is computed, skip first ngram_len - 1 tokens
# eos_mask will be of shape [batch_size, output_len]
eos_token_mask = self.logits_processor.compute_eos_token_mask(
input_ids=tokenized_outputs,
eos_token_id=self.tokenizer.eos_token_id,
)[:, self.logits_processor.ngram_len - 1 :]
# context repetition mask is computed
context_repetition_mask = self.logits_processor.compute_context_repetition_mask(
input_ids=tokenized_outputs,
)
# context repitition mask shape [batch_size, output_len - (ngram_len - 1)]
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combined_mask = context_repetition_mask * eos_token_mask
g_values = self.logits_processor.compute_g_values(
input_ids=tokenized_outputs,
)
# g values shape [batch_size, output_len - (ngram_len - 1), depth]
return self.detector_module(g_values, combined_mask)
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class BeamScorer(ABC):
"""
Abstract base class for all beam scorers that are used for [`~PreTrainedModel.beam_search`] and
[`~PreTrainedModel.beam_sample`].
"""
@abstractmethod
@add_start_docstrings(PROCESS_INPUTS_DOCSTRING)
def process(
self,
input_ids: torch.LongTensor,
next_scores: torch.FloatTensor,
next_tokens: torch.LongTensor,
next_indices: torch.LongTensor,
**kwargs,
) -> Tuple[torch.Tensor]:
raise NotImplementedError("This is an abstract method.")
@abstractmethod
@add_start_docstrings(FINALIZE_INPUTS_DOCSTRING)
def finalize(
self,
input_ids: torch.LongTensor,
next_scores: torch.FloatTensor,
next_tokens: torch.LongTensor,
next_indices: torch.LongTensor,
max_length: int,
**kwargs,
) -> torch.LongTensor:
raise NotImplementedError("This is an abstract method.")
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class BeamSearchScorer(BeamScorer):
r"""
[`BeamScorer`] implementing standard beam search decoding.
Adapted in part from [Facebook's XLM beam search
code](https://github.com/facebookresearch/XLM/blob/9e6f6814d17be4fe5b15f2e6c43eb2b2d76daeb4/src/model/transformer.py#L529).
Reference for the diverse beam search algorithm and implementation [Ashwin Kalyan's DBS
implementation](https://github.com/ashwinkalyan/dbs/blob/master/dbs/beam_utils.lua)
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Args:
batch_size (`int`):
Batch Size of `input_ids` for which standard beam search decoding is run in parallel.
num_beams (`int`):
Number of beams for beam search.
device (`torch.device`):
Defines the device type (*e.g.*, `"cpu"` or `"cuda"`) on which this instance of `BeamSearchScorer` will be
allocated.
length_penalty (`float`, *optional*, defaults to 1.0):
Exponential penalty to the length that is used with beam-based generation. It is applied as an exponent to
the sequence length, which in turn is used to divide the score of the sequence. Since the score is the log
likelihood of the sequence (i.e. negative), `length_penalty` > 0.0 promotes longer sequences, while
`length_penalty` < 0.0 encourages shorter sequences.
do_early_stopping (`bool` or `str`, *optional*, defaults to `False`):
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Controls the stopping condition for beam-based methods, like beam-search. It accepts the following values:
`True`, where the generation stops as soon as there are `num_beams` complete candidates; `False`, where an
heuristic is applied and the generation stops when is it very unlikely to find better candidates;
`"never"`, where the beam search procedure only stops when there cannot be better candidates (canonical
beam search algorithm).
num_beam_hyps_to_keep (`int`, *optional*, defaults to 1):
The number of beam hypotheses that shall be returned upon calling
[`~transformers.BeamSearchScorer.finalize`].
num_beam_groups (`int`, *optional*, defaults to 1):
Number of groups to divide `num_beams` into in order to ensure diversity among different groups of beams.
See [this paper](https://arxiv.org/pdf/1610.02424.pdf) for more details.
max_length (`int`, *optional*):
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The maximum length of the sequence to be generated.
"""
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def __init__(
self,
batch_size: int,
num_beams: int,
device: torch.device,
length_penalty: Optional[float] = 1.0,
do_early_stopping: Optional[Union[bool, str]] = False,
num_beam_hyps_to_keep: Optional[int] = 1,
num_beam_groups: Optional[int] = 1,
max_length: Optional[int] = None,
):
self.num_beams = num_beams
self.device = device
self.length_penalty = length_penalty
self.do_early_stopping = do_early_stopping
self.num_beam_hyps_to_keep = num_beam_hyps_to_keep
self.num_beam_groups = num_beam_groups
self.group_size = self.num_beams // self.num_beam_groups
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self._is_init = False
# self._beam_hyps[i*self.num_beam_groups+j] is the beam_hyps of the j-th group in the i-th mini-batch.
# If group_beam_search is not used, the list consists of `batch_size` beam_hyps.
self._beam_hyps = [
BeamHypotheses(
num_beams=self.group_size,
length_penalty=self.length_penalty,
early_stopping=self.do_early_stopping,
max_length=max_length,
)
for _ in range(batch_size * self.num_beam_groups)
]
# self._done[i*self.num_beam_groups+j] indicates whether the generation of the beam_hyps of the j-th group
# in the i-th mini-batch is complete.
self._done = torch.tensor(
[False for _ in range(batch_size * self.num_beam_groups)], dtype=torch.bool, device=self.device
)
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if not isinstance(num_beams, int) or num_beams <= 1:
raise ValueError(
f"`num_beams` has to be an integer strictly greater than 1, but is {num_beams}. For `num_beams` == 1,"
" one should make use of `greedy_search` instead."
)
if not isinstance(num_beam_groups, int) or (num_beam_groups > num_beams) or (num_beams % num_beam_groups != 0):
raise ValueError(
"`num_beam_groups` has to be an integer smaller or equal than `num_beams` and `num_beams` has to be"
f" divisible by `num_beam_groups`, but is {num_beam_groups} with `num_beams` being {num_beams}."
)
@property
def is_done(self) -> bool:
return self._done.all()
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def process(
self,
input_ids: torch.LongTensor,
next_scores: torch.FloatTensor,
next_tokens: torch.LongTensor,
next_indices: torch.LongTensor,
pad_token_id: Optional[Union[int, torch.Tensor]] = None,
eos_token_id: Optional[Union[int, List[int], torch.Tensor]] = None,
beam_indices: Optional[torch.LongTensor] = None,
group_index: Optional[int] = 0,
decoder_prompt_len: Optional[int] = 0,
) -> Dict[str, torch.Tensor]:
# add up to the length which the next_scores is calculated on (including decoder prompt)
cur_len = input_ids.shape[-1] + 1
batch_size = len(self._beam_hyps) // self.num_beam_groups
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if not (batch_size == (input_ids.shape[0] // self.group_size)):
if self.num_beam_groups > 1:
raise ValueError(
f"A group beam size of {input_ids.shape[0]} is used as the input, but a group beam "
f"size of {self.group_size} is expected by the beam scorer."
)
else:
raise ValueError(
f"A beam size of {input_ids.shape[0]} is used as the input, but a beam size of "
f"{self.group_size} is expected by the beam scorer."
)
device = input_ids.device
next_beam_scores = torch.zeros((batch_size, self.group_size), dtype=next_scores.dtype, device=device)
next_beam_tokens = torch.zeros((batch_size, self.group_size), dtype=next_tokens.dtype, device=device)
next_beam_indices = torch.zeros((batch_size, self.group_size), dtype=next_indices.dtype, device=device)
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if eos_token_id is not None and not isinstance(eos_token_id, torch.Tensor):
if isinstance(eos_token_id, int):
eos_token_id = [eos_token_id]
eos_token_id = torch.tensor(eos_token_id)
for batch_idx in range(batch_size):
batch_group_idx = batch_idx * self.num_beam_groups + group_index
if self._done[batch_group_idx]:
if self.num_beams < len(self._beam_hyps[batch_group_idx]):
raise ValueError(f"Batch can only be done if at least {self.num_beams} beams have been generated")
if eos_token_id is None or pad_token_id is None:
raise ValueError("Generated beams >= num_beams -> eos_token_id and pad_token have to be defined")
# pad the batch
next_beam_scores[batch_idx, :] = 0
next_beam_tokens[batch_idx, :] = pad_token_id
next_beam_indices[batch_idx, :] = 0
continue
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# next tokens for this sentence
beam_idx = 0
for beam_token_rank, (next_token, next_score, next_index) in enumerate(
zip(next_tokens[batch_idx], next_scores[batch_idx], next_indices[batch_idx])
):
batch_beam_idx = batch_idx * self.group_size + next_index
# add to generated hypotheses if end of sentence
if (eos_token_id is not None) and (next_token.item() in eos_token_id):
# if beam_token does not belong to top num_beams tokens, it should not be added
is_beam_token_worse_than_top_num_beams = beam_token_rank >= self.group_size
if is_beam_token_worse_than_top_num_beams:
continue
if beam_indices is not None:
beam_index = beam_indices[batch_beam_idx]
beam_index = beam_index + (batch_beam_idx,)
else:
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beam_index = None
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self._beam_hyps[batch_group_idx].add(
input_ids[batch_beam_idx].clone(),
next_score.item(),
beam_indices=beam_index,
generated_len=cur_len - decoder_prompt_len,
)
else:
# add next predicted token since it is not eos_token
next_beam_scores[batch_idx, beam_idx] = next_score
next_beam_tokens[batch_idx, beam_idx] = next_token
next_beam_indices[batch_idx, beam_idx] = batch_beam_idx
beam_idx += 1
# once the beam for next step is full, don't add more tokens to it.
if beam_idx == self.group_size:
break
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if beam_idx < self.group_size:
raise ValueError(
f"At most {self.group_size} tokens in {next_tokens[batch_idx]} can be equal to `eos_token_id:"
f" {eos_token_id}`. Make sure {next_tokens[batch_idx]} are corrected."
)
# Check if we are done so that we can save a pad step if all(done)
self._done[batch_group_idx] = self._done[batch_group_idx] or self._beam_hyps[batch_group_idx].is_done(
next_scores[batch_idx].max().item(), cur_len, decoder_prompt_len
)
return UserDict(
{
"next_beam_scores": next_beam_scores.view(-1),
"next_beam_tokens": next_beam_tokens.view(-1),
"next_beam_indices": next_beam_indices.view(-1),
}
)
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def finalize(
self,
input_ids: torch.LongTensor,
final_beam_scores: torch.FloatTensor,
final_beam_tokens: torch.LongTensor,
final_beam_indices: torch.LongTensor,
max_length: int,
pad_token_id: Optional[Union[int, torch.Tensor]] = None,
eos_token_id: Optional[Union[int, List[int], torch.Tensor]] = None,
beam_indices: Optional[torch.LongTensor] = None,
decoder_prompt_len: Optional[int] = 0,
) -> Tuple[torch.LongTensor]:
batch_size = len(self._beam_hyps) // self.num_beam_groups
if eos_token_id is not None and not isinstance(eos_token_id, torch.Tensor):
if isinstance(eos_token_id, int):
eos_token_id = [eos_token_id]
eos_token_id = torch.tensor(eos_token_id)
# finalize all open beam hypotheses and add to generated hypotheses
for batch_group_idx, beam_hyp in enumerate(self._beam_hyps):
if self._done[batch_group_idx]:
continue
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# all open beam hypotheses are added to the beam hypothesis
# beam hypothesis class automatically keeps the best beams
for index_per_group in range(self.group_size):
batch_beam_idx = batch_group_idx * self.group_size + index_per_group
final_score = final_beam_scores[batch_beam_idx].item()
final_tokens = input_ids[batch_beam_idx]
beam_index = beam_indices[batch_beam_idx] if beam_indices is not None else None
generated_len = final_tokens.shape[-1] - decoder_prompt_len
beam_hyp.add(final_tokens, final_score, beam_indices=beam_index, generated_len=generated_len)
# select the best hypotheses
sent_lengths = input_ids.new(batch_size * self.num_beam_hyps_to_keep)
best = []
best_indices = []
best_scores = torch.zeros(batch_size * self.num_beam_hyps_to_keep, device=self.device, dtype=torch.float32)
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# retrieve best hypotheses
for i in range(batch_size):
beam_hyps_in_batch = self._beam_hyps[i * self.num_beam_groups : (i + 1) * self.num_beam_groups]
candidate_beams = [beam for beam_hyp in beam_hyps_in_batch for beam in beam_hyp.beams]
sorted_hyps = sorted(candidate_beams, key=lambda x: x[0])
for j in range(self.num_beam_hyps_to_keep):
best_hyp_tuple = sorted_hyps.pop()
best_score = best_hyp_tuple[0]
best_hyp = best_hyp_tuple[1]
best_index = best_hyp_tuple[2]
sent_lengths[self.num_beam_hyps_to_keep * i + j] = len(best_hyp)
# append hyp to lists
best.append(best_hyp)
# append indices to list
best_indices.append(best_index)
best_scores[i * self.num_beam_hyps_to_keep + j] = best_score
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# prepare for adding eos
sent_lengths_max = sent_lengths.max().item() + 1
sent_max_len = min(sent_lengths_max, max_length) if max_length is not None else sent_lengths_max
decoded: torch.LongTensor = input_ids.new(batch_size * self.num_beam_hyps_to_keep, sent_max_len)
if len(best_indices) > 0 and best_indices[0] is not None:
indices: torch.LongTensor = input_ids.new(batch_size * self.num_beam_hyps_to_keep, sent_max_len)
else:
indices = None
# shorter batches are padded if needed
if sent_lengths.min().item() != sent_lengths.max().item():
if pad_token_id is None:
raise ValueError("`pad_token_id` has to be defined")
decoded.fill_(pad_token_id)
if indices is not None:
indices.fill_(-1)
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# fill with hypotheses and eos_token_id if the latter fits in
for i, (hypo, best_idx) in enumerate(zip(best, best_indices)):
decoded[i, : sent_lengths[i]] = hypo
if indices is not None:
indices[i, : len(best_idx)] = torch.tensor(best_idx)
if sent_lengths[i] < sent_max_len:
# inserting only the first eos_token_id
decoded[i, sent_lengths[i]] = eos_token_id[0]
return UserDict(
{
"sequences": decoded,
"sequence_scores": best_scores,
"beam_indices": indices,
}
)
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class ConstrainedBeamSearchScorer(BeamScorer):
r"""
[`BeamScorer`] implementing constrained beam search decoding.
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Args:
batch_size (`int`):
Batch Size of `input_ids` for which standard beam search decoding is run in parallel.
num_beams (`int`):
Number of beams for beam search.
constraints (`List[Constraint]`):
A list of positive constraints represented as `Constraint` objects that must be fulfilled in the generation
output. For more information, the documentation of [`Constraint`] should be read.
device (`torch.device`):
Defines the device type (*e.g.*, `"cpu"` or `"cuda"`) on which this instance of `BeamSearchScorer` will be
allocated.
length_penalty (`float`, *optional*, defaults to 1.0):
Exponential penalty to the length that is used with beam-based generation. It is applied as an exponent to
the sequence length, which in turn is used to divide the score of the sequence. Since the score is the log
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likelihood of the sequence (i.e. negative), `length_penalty` > 0.0 promotes longer sequences, while
`length_penalty` < 0.0 encourages shorter sequences.
do_early_stopping (`bool` or `str`, *optional*, defaults to `False`):
Controls the stopping condition for beam-based methods, like beam-search. It accepts the following values:
`True`, where the generation stops as soon as there are `num_beams` complete candidates; `False`, where an
heuristic is applied and the generation stops when is it very unlikely to find better candidates;
`"never"`, where the beam search procedure only stops when there cannot be better candidates (canonical
beam search algorithm).
num_beam_hyps_to_keep (`int`, *optional*, defaults to 1):
The number of beam hypotheses that shall be returned upon calling
[`~transformers.BeamSearchScorer.finalize`].
num_beam_groups (`int`, *optional*, defaults to 1):
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Number of groups to divide `num_beams` into in order to ensure diversity among different groups of beams.
See [this paper](https://arxiv.org/pdf/1610.02424.pdf) for more details.
max_length (`int`, *optional*):
The maximum length of the sequence to be generated.
"""
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def __init__(
self,
batch_size: int,
num_beams: int,
constraints: List[Constraint],
device: torch.device,
length_penalty: Optional[float] = 1.0,
do_early_stopping: Optional[Union[bool, str]] = False,
num_beam_hyps_to_keep: Optional[int] = 1,
num_beam_groups: Optional[int] = 1,
max_length: Optional[int] = None,
):
self.num_beams = num_beams
self.device = device
self.length_penalty = length_penalty
self.do_early_stopping = do_early_stopping
self.num_beam_hyps_to_keep = num_beam_hyps_to_keep
self.num_beam_groups = num_beam_groups
self.group_size = self.num_beams // self.num_beam_groups
self.constraints = constraints
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self._is_init = False
self._beam_hyps = [
BeamHypotheses(
num_beams=self.num_beams,
length_penalty=self.length_penalty,
early_stopping=self.do_early_stopping,
max_length=max_length,
)
for _ in range(batch_size)
]
self._done = torch.tensor([False for _ in range(batch_size)], dtype=torch.bool, device=self.device)
if not isinstance(num_beams, int) or num_beams <= 1:
raise ValueError(
f"`num_beams` has to be an integer strictly greater than 1, but is {num_beams}. For `num_beams` == 1,"
" one should make use of `greedy_search` instead."
)
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if not isinstance(num_beam_groups, int) or (num_beam_groups > num_beams) or (num_beams % num_beam_groups != 0):
raise ValueError(
"`num_beam_groups` has to be an integer smaller or equal than `num_beams` and `num_beams` has to be"
f" divisible by `num_beam_groups`, but is {num_beam_groups} with `num_beams` being {num_beams}."
)
@property
def is_done(self) -> bool:
return self._done.all()
def make_constraint_states(self, n):
return [ConstraintListState([constraint.copy() for constraint in self.constraints]) for _ in range(n)]
def check_completes_constraints(self, sequence):
new_state = self.make_constraint_states(1)[0]
new_state.reset(sequence)
return new_state.completed
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def process(
self,
input_ids: torch.LongTensor,
next_scores: torch.FloatTensor,
next_tokens: torch.LongTensor,
next_indices: torch.LongTensor,
scores_for_all_vocab: torch.FloatTensor,
pad_token_id: Optional[Union[int, torch.Tensor]] = None,
eos_token_id: Optional[Union[int, List[int], torch.Tensor]] = None,
beam_indices: Optional[torch.LongTensor] = None,
decoder_prompt_len: Optional[int] = 0,
) -> Tuple[torch.Tensor]:
r"""
Args:
input_ids (`torch.LongTensor` of shape `(batch_size * num_beams, sequence_length)`):
Indices of input sequence tokens in the vocabulary.
Indices can be obtained using any class inheriting from [`PreTrainedTokenizer`]. See
[`PreTrainedTokenizer.encode`] and [`PreTrainedTokenizer.__call__`] for details.
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[What are input IDs?](../glossary#input-ids)
next_scores (`torch.FloatTensor` of shape `(batch_size, 2 * num_beams)`):
Current scores of the top `2 * num_beams` non-finished beam hypotheses.
next_tokens (`torch.LongTensor` of shape `(batch_size, 2 * num_beams)`):
`input_ids` of the tokens corresponding to the top `2 * num_beams` non-finished beam hypotheses.
next_indices (`torch.LongTensor` of shape `(batch_size, 2 * num_beams)`):
Beam indices indicating to which beam hypothesis the `next_tokens` correspond.
scores_for_all_vocab (`torch.FloatTensor` of shape `(batch_size * num_beams, sequence_length)`):
The scores of all tokens in the vocabulary for each of the beam hypotheses.
pad_token_id (`int`, *optional*):
The id of the *padding* token.
eos_token_id (`Union[int, List[int]]`, *optional*):
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The id of the *end-of-sequence* token. Optionally, use a list to set multiple *end-of-sequence* tokens.
beam_indices (`torch.LongTensor`, *optional*):
Beam indices indicating to which beam hypothesis each token correspond.
decoder_prompt_len (`int`, *optional*):
The length of prompt that is included in the input to decoder.
Return:
`UserDict`: A dictionary composed of the fields as defined above:
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- **next_beam_scores** (`torch.FloatTensor` of shape `(batch_size * num_beams)`) -- Updated scores of
all
non-finished beams.
- **next_beam_tokens** (`torch.FloatTensor` of shape `(batch_size * num_beams)`) -- Next tokens to be
added
to the non-finished beam_hypotheses.
- **next_beam_indices** (`torch.FloatTensor` of shape `(batch_size * num_beams)`) -- Beam indices
indicating to which beam the next tokens shall be added.
"""
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# add up to the length which the next_scores is calculated on (including decoder prompt)
cur_len = input_ids.shape[-1] + 1
batch_size = len(self._beam_hyps)
if not (batch_size == (input_ids.shape[0] // self.group_size)):
if self.num_beam_groups > 1:
raise ValueError(
f"A group beam size of {input_ids.shape[0]} is used as the input, but a group beam "
f"size of {self.group_size} is expected by the beam scorer."
)
else:
raise ValueError(
f"A beam size of {input_ids.shape[0]} is used as the input, but a beam size of "
f"{self.group_size} is expected by the beam scorer."
)
device = input_ids.device
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next_beam_scores = torch.zeros((batch_size, self.group_size), dtype=next_scores.dtype, device=device)
next_beam_tokens = torch.zeros((batch_size, self.group_size), dtype=next_tokens.dtype, device=device)
next_beam_indices = torch.zeros((batch_size, self.group_size), dtype=next_indices.dtype, device=device)
if eos_token_id is not None and not isinstance(eos_token_id, torch.Tensor):
if isinstance(eos_token_id, int):
eos_token_id = [eos_token_id]
eos_token_id = torch.tensor(eos_token_id)
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for batch_idx, beam_hyp in enumerate(self._beam_hyps):
if self._done[batch_idx]:
if self.num_beams < len(beam_hyp):
raise ValueError(f"Batch can only be done if at least {self.num_beams} beams have been generated")
if eos_token_id is None or pad_token_id is None:
raise ValueError("Generated beams >= num_beams -> eos_token_id and pad_token have to be defined")
# pad the batch
next_beam_scores[batch_idx, :] = 0
next_beam_tokens[batch_idx, :] = pad_token_id
next_beam_indices[batch_idx, :] = 0
continue
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# next tokens for this sentence.
beam_idx = 0
for beam_token_rank, (next_token, next_score, next_index) in enumerate(
zip(next_tokens[batch_idx], next_scores[batch_idx], next_indices[batch_idx])
):
batch_beam_idx = batch_idx * self.group_size + next_index
# add to generated hypotheses if end of sentence
if (eos_token_id is not None) and (next_token.item() in eos_token_id):
# if beam_token does not belong to top num_beams tokens, it should not be added
is_beam_token_worse_than_top_num_beams = beam_token_rank >= self.group_size
if is_beam_token_worse_than_top_num_beams:
continue
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completes_constraint = self.check_completes_constraints(input_ids[batch_beam_idx].cpu().tolist())
if completes_constraint:
if beam_indices is not None:
beam_index = beam_indices[batch_beam_idx]
beam_index = beam_index + (batch_beam_idx,)
else:
beam_index = None
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beam_hyp.add(
input_ids[batch_beam_idx].clone(),
next_score.item(),
beam_indices=beam_index,
generated_len=cur_len - decoder_prompt_len,
)
else:
# add next predicted token since it is not eos_token
next_beam_scores[batch_idx, beam_idx] = next_score
next_beam_tokens[batch_idx, beam_idx] = next_token
next_beam_indices[batch_idx, beam_idx] = batch_beam_idx
beam_idx += 1
# once the beam for next step is full, don't add more tokens to it.
if beam_idx == self.group_size:
break
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new_scores, new_tokens, new_indices = self.step_sentence_constraint(
batch_idx,
input_ids,
scores_for_all_vocab,
next_beam_scores[batch_idx],
next_beam_tokens[batch_idx],
next_beam_indices[batch_idx],
)
next_beam_scores[batch_idx] = new_scores
next_beam_tokens[batch_idx] = new_tokens
next_beam_indices[batch_idx] = new_indices
if beam_idx < self.group_size:
raise ValueError(
f"At most {self.group_size} tokens in {next_tokens[batch_idx]} can be equal to `eos_token_id:"
f" {eos_token_id}`. Make sure {next_tokens[batch_idx]} are corrected."
)
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# Check if we are done so that we can save a pad step if all(done)
self._done[batch_idx] = self._done[batch_idx] or beam_hyp.is_done(
next_scores[batch_idx].max().item(), cur_len, decoder_prompt_len
)
return UserDict(
{
"next_beam_scores": next_beam_scores.view(-1),
"next_beam_tokens": next_beam_tokens.view(-1),
"next_beam_indices": next_beam_indices.view(-1),
}
)
def step_sentence_constraint(
self,
batch_idx: int,
input_ids: torch.LongTensor,
vocab_scores: torch.FloatTensor,
sent_beam_scores: torch.FloatTensor,
sent_beam_tokens: torch.LongTensor,
sent_beam_indices: torch.LongTensor,
push_progress: bool = False,
):
# sent_beam_tokens are the next {num_beams} number of tokens that are under consideration for this beam
# (candidate next tokens)
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# 1. Adding "advance_tokens"
# using ConstraintStateList.advance(), we propose new tokens to be added into this "candidate list" that will
# advance us in fulfilling the constraints.
# 2. Selecting best candidates such that we end up with highest probable candidates
# that fulfill our constraints.
orig_len = sent_beam_indices.size(0)
device = sent_beam_indices.device
# initialize states
topk_contraint_states = self.make_constraint_states(orig_len)
advance_constraint_states = self.make_constraint_states(orig_len)
sidx, eidx = batch_idx * orig_len, (batch_idx + 1) * orig_len
this_batch_input_ids = input_ids[sidx:eidx]
this_batch_token_scores = vocab_scores[sidx:eidx]
full_hypotheses = torch.cat((input_ids[sent_beam_indices], sent_beam_tokens.unsqueeze(-1)), dim=-1)
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# need to make new hypothesis that advance the constraints
track_new = {
"new_seqs": full_hypotheses.tolist(),
"new_states": [],
"new_indices": [],
"new_tokens": [],
"new_scores": [],
}
for seq_idx, pre_seq in enumerate(this_batch_input_ids):
# pre_seq = ith sequence generated before this step.
# input_ids -> (topk) generic beam search best model next tokens
# -> (advance) constraints forcing the next token
# either way, we need to sort them into "banks" later, so store a "ConstraintListState" for all types of
# hypotheses.
topk_state = topk_contraint_states[seq_idx]
topk_state.reset(full_hypotheses[seq_idx].cpu().tolist())
advance_state = advance_constraint_states[seq_idx]
advance_state.reset(pre_seq.cpu().tolist())
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if not advance_state.completed:
advance_tokens = torch.LongTensor(advance_state.advance()).to(device)
for advance_token in advance_tokens:
# since adding each `advance_token` leads to a different hypothesis, create new state instance.
new_state = advance_state.copy(stateful=True)
new_state.add(advance_token.cpu().tolist())
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advance_seq = torch.cat((pre_seq, advance_token.unsqueeze(0)), -1).cpu().tolist()
if advance_seq not in track_new["new_seqs"]:
# prevent duplicates, which are basically bound to happen in this process.
track_new["new_seqs"].append(advance_seq)
track_new["new_indices"].append(sidx + seq_idx) # idx -> global idx across all the batches
track_new["new_tokens"].append(advance_token)
track_new["new_scores"].append(this_batch_token_scores[seq_idx].take(advance_token))
track_new["new_states"].append(new_state)
elif push_progress:
# Basically, `sent_beam_indices` often chooses very little among `input_ids` the generated sequences that
# actually fulfill our constraints. For example, let constraints == ["loves pies"] and
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# pre_seq_1 = "The child loves pies and" pre_seq_2 = "The child plays in the playground and"
# Without this step, if `sent_beam_indices` is something like [1,1], then
# 1. `pre_seq_1` won't be added to the list of (topk) hypothesis since it's not in the indices and
# 2. it won't be added to the list of (advance) hypothesis since it's completed already. (this is
# the else part of `if constraints_completed[seq_idx]`)
# 3. it ends up simply getting removed from consideration.
# #3 might be fine and actually desired, since it's likely that it's a low-probability output anyways,
# especially if it's not in the list of `sent_beam_indices`. But this often leads to lengthened beam
# search times, since completed sequences keep getting removed after all this effort for constrained
# generation.
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# Here, we basically take `pre_seq_1` and to "push" it into the considered list of hypotheses, by simply
# appending the next likely token in the vocabulary and adding it to the list of hypotheses.
new_score, new_token = torch.max(this_batch_token_scores[seq_idx], 0) # some next probable token
advance_seq = torch.cat((pre_seq, new_token.unsqueeze(0)), -1)
advance_state = advance_constraint_states[seq_idx]
advance_seq = advance_seq.cpu().tolist()
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advance_state.reset(advance_seq)
if advance_seq not in track_new["new_seqs"]:
# but still don't want to have duplicates
track_new["new_seqs"].append(advance_seq)
track_new["new_indices"].append(seq_idx)
track_new["new_tokens"].append(new_token)
track_new["new_scores"].append(new_score)
track_new["new_states"].append(advance_state)
if len(track_new["new_indices"]) > 0:
new_indices = torch.tensor(track_new["new_indices"]).to(device)
new_tokens = torch.stack(track_new["new_tokens"]).to(device)
new_scores = torch.stack(track_new["new_scores"]).to(device)
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all_states = topk_contraint_states + track_new["new_states"]
all_tokens = torch.cat((sent_beam_tokens, new_tokens), -1)
all_scores = torch.cat((sent_beam_scores, new_scores), -1)
all_banks = torch.tensor([one.get_bank() for one in all_states]).to(device)
zipped = all_banks * 100 + all_scores
indices = zipped.sort(descending=True).indices
sorted_banks = all_banks[indices]
# Then we end up with {sorted among bank C}, {sorted among bank C-1}, ..., {sorted among bank 0}
counter = -1
cur_bank = sorted_banks[0]
increments = []
for bank in sorted_banks:
if bank == cur_bank:
counter += 1
else:
counter = 0
cur_bank = bank
increments.append(counter)
rearrangers = torch.tensor(np.argsort(increments, kind="mergesort"))
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indices = indices[rearrangers][:orig_len]
sent_beam_scores = all_scores[indices]
sent_beam_tokens = all_tokens[indices]
sent_beam_indices = torch.cat((sent_beam_indices, new_indices))[indices]
return sent_beam_scores, sent_beam_tokens, sent_beam_indices
def finalize(
self,
input_ids: torch.LongTensor,
final_beam_scores: torch.FloatTensor,
final_beam_tokens: torch.LongTensor,
final_beam_indices: torch.LongTensor,
max_length: int,
pad_token_id: Optional[Union[int, torch.Tensor]] = None,
eos_token_id: Optional[Union[int, List[int], torch.Tensor]] = None,
beam_indices: Optional[torch.LongTensor] = None,
decoder_prompt_len: Optional[int] = 0,
) -> Tuple[torch.LongTensor]:
batch_size = len(self._beam_hyps)
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if eos_token_id is not None and not isinstance(eos_token_id, torch.Tensor):
if isinstance(eos_token_id, int):
eos_token_id = [eos_token_id]
eos_token_id = torch.tensor(eos_token_id)
# finalize all open beam hypotheses and add to generated hypotheses
for batch_idx, beam_hyp in enumerate(self._beam_hyps):
if self._done[batch_idx]:
continue
# all open beam hypotheses are added to the beam hypothesis
# beam hypothesis class automatically keeps the best beams
ids_collect = []
for beam_id in range(self.num_beams):
batch_beam_idx = batch_idx * self.num_beams + beam_id
final_score = final_beam_scores[batch_beam_idx].item()
final_tokens = input_ids[batch_beam_idx]
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completes_constraint = self.check_completes_constraints(final_tokens.cpu().tolist())
if completes_constraint:
beam_index = beam_indices[batch_beam_idx] if beam_indices is not None else None
generated_len = final_tokens.shape[-1] - decoder_prompt_len
beam_hyp.add(final_tokens, final_score, beam_indices=beam_index, generated_len=generated_len)
ids_collect.append(beam_id)
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# due to overly complex constraints or other factors, sometimes we can't gaurantee a successful
# generation. In these cases we simply return the highest scoring outputs.
if len(ids_collect) < self.num_beam_hyps_to_keep:
for beam_id in range(self.num_beams):
if beam_id not in ids_collect:
batch_beam_idx = batch_idx * self.num_beams + beam_id
final_score = final_beam_scores[batch_beam_idx].item()
final_tokens = input_ids[batch_beam_idx]
generated_len = final_tokens.shape[-1] - decoder_prompt_len
beam_hyp.add(final_tokens, final_score, generated_len=generated_len)
if len(ids_collect) >= self.num_beam_hyps_to_keep:
break
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# select the best hypotheses
sent_lengths = input_ids.new(batch_size * self.num_beam_hyps_to_keep)
best = []
best_indices = []
best_scores = torch.zeros(batch_size * self.num_beam_hyps_to_keep, device=self.device, dtype=torch.float32)
# retrieve best hypotheses
for i, beam_hyp in enumerate(self._beam_hyps):
sorted_hyps = sorted(beam_hyp.beams, key=lambda x: x[0])
for j in range(self.num_beam_hyps_to_keep):
best_hyp_tuple = sorted_hyps.pop()
best_score = best_hyp_tuple[0]
best_hyp = best_hyp_tuple[1]
best_index = best_hyp_tuple[2]
sent_lengths[self.num_beam_hyps_to_keep * i + j] = len(best_hyp)
# append to lists
best.append(best_hyp)
# append indices to list
best_indices.append(best_index)
best_scores[i * self.num_beam_hyps_to_keep + j] = best_score
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# prepare for adding eos
sent_lengths_max = sent_lengths.max().item() + 1
sent_max_len = min(sent_lengths_max, max_length) if max_length is not None else sent_lengths_max
decoded: torch.LongTensor = input_ids.new(batch_size * self.num_beam_hyps_to_keep, sent_max_len)
if len(best_indices) > 0 and best_indices[0] is not None:
indices: torch.LongTensor = input_ids.new(batch_size * self.num_beam_hyps_to_keep, sent_max_len)
else:
indices = None
# shorter batches are padded if needed
if sent_lengths.min().item() != sent_lengths.max().item():
if pad_token_id is None:
raise ValueError("`pad_token_id` has to be defined")
decoded.fill_(pad_token_id)
if indices is not None:
indices.fill_(-1)
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# fill with hypotheses and eos_token_id if the latter fits in
for i, (hypo, best_idx) in enumerate(zip(best, best_indices)):
decoded[i, : sent_lengths[i]] = hypo
if indices is not None:
indices[i, : len(best_idx)] = torch.tensor(best_idx)
if sent_lengths[i] < sent_max_len:
# inserting only the first eos_token_id
decoded[i, sent_lengths[i]] = eos_token_id[0]
return UserDict(
{
"sequences": decoded,
"sequence_scores": best_scores,
"beam_indices": indices,
}
)
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class BeamHypotheses:
def __init__(self, num_beams: int, length_penalty: float, early_stopping: bool, max_length: Optional[int] = None):
"""
Initialize n-best list of hypotheses.
"""
self.length_penalty = length_penalty
self.early_stopping = early_stopping
self.max_length = max_length
self.num_beams = num_beams
self.beams = []
self.worst_score = 1e9
if not isinstance(self.early_stopping, bool) and self.max_length is None:
raise ValueError(
"When `do_early_stopping` is set to a string, `max_length` must be defined. Ensure it is passed to the"
" BeamScorer class instance at initialization time."
)
def __len__(self):
"""
Number of hypotheses in the list.
"""
return len(self.beams)
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def add(
self,
hyp: torch.LongTensor,
sum_logprobs: float,
beam_indices: Optional[torch.LongTensor] = None,
generated_len: Optional[int] = None,
):
"""
Add a new hypothesis to the list.
"""
if generated_len is not None:
score = sum_logprobs / (generated_len**self.length_penalty)
# This 'else' case exists for retrocompatibility
else:
score = sum_logprobs / (hyp.shape[-1] ** self.length_penalty)
if len(self) < self.num_beams or score > self.worst_score:
self.beams.append((score, hyp, beam_indices))
if len(self) > self.num_beams:
sorted_next_scores = sorted([(s, idx) for idx, (s, _, _) in enumerate(self.beams)])
del self.beams[sorted_next_scores[0][1]]
self.worst_score = sorted_next_scores[1][0]
else:
self.worst_score = min(score, self.worst_score)
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def is_done(self, best_sum_logprobs: float, cur_len: int, decoder_prompt_len: Optional[int] = 0) -> bool:
"""
If there are enough hypotheses and that none of the hypotheses being generated can become better than the worst
one in the heap, then we are done with this sentence.
"""
if len(self) < self.num_beams:
return False
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# `True`: stop as soon as at least `num_beams` hypotheses are finished
if self.early_stopping is True:
return True
# `False`: heuristic -- compute best possible score from `cur_len`, even though it is not entirely accurate
# when `length_penalty` is positive. See the discussion below for more details.
# https://github.com/huggingface/transformers/pull/20901#issuecomment-1369845565
elif self.early_stopping is False:
highest_attainable_score = best_sum_logprobs / (cur_len - decoder_prompt_len) ** self.length_penalty
ret = self.worst_score >= highest_attainable_score
return ret
# `"never"`: compute the best possible score, depending on the signal of `length_penalty`
else:
# `length_penalty` > 0.0 -> max denominator is obtaned from `max_length`, not from `cur_len` -> min
# abs(`highest_attainable_score`) is obtained -> `highest_attainable_score` is negative, hence we obtain
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# its max this way
if self.length_penalty > 0.0:
if self.max_length <= decoder_prompt_len:
raise ValueError("max_length is not larger than decoder prompt length")
highest_attainable_score = (
best_sum_logprobs / (self.max_length - decoder_prompt_len) ** self.length_penalty
)
# the opposite logic applies here (max `highest_attainable_score` from `cur_len`)
else:
highest_attainable_score = best_sum_logprobs / (cur_len - decoder_prompt_len) ** self.length_penalty
ret = self.worst_score >= highest_attainable_score
return ret
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class BaseStreamer:
"""
Base class from which `.generate()` streamers should inherit.
"""
def put(self, value):
"""Function that is called by `.generate()` to push new tokens"""
raise NotImplementedError()
def end(self):
"""Function that is called by `.generate()` to signal the end of generation"""
raise NotImplementedError()
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class TextStreamer(BaseStreamer):
"""
Simple text streamer that prints the token(s) to stdout as soon as entire words are formed.
<Tip warning={true}>
The API for the streamer classes is still under development and may change in the future.
</Tip>
Parameters:
tokenizer (`AutoTokenizer`):
The tokenized used to decode the tokens.
skip_prompt (`bool`, *optional*, defaults to `False`):
Whether to skip the prompt to `.generate()` or not. Useful e.g. for chatbots.
decode_kwargs (`dict`, *optional*):
Additional keyword arguments to pass to the tokenizer's `decode` method.
Examples:
```python
>>> from transformers import AutoModelForCausalLM, AutoTokenizer, TextStreamer
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>>> tok = AutoTokenizer.from_pretrained("openai-community/gpt2")
>>> model = AutoModelForCausalLM.from_pretrained("openai-community/gpt2")
>>> inputs = tok(["An increasing sequence: one,"], return_tensors="pt")
>>> streamer = TextStreamer(tok)
>>> # Despite returning the usual output, the streamer will also print the generated text to stdout.
>>> _ = model.generate(**inputs, streamer=streamer, max_new_tokens=20)
An increasing sequence: one, two, three, four, five, six, seven, eight, nine, ten, eleven,
```
"""
def __init__(self, tokenizer: "AutoTokenizer", skip_prompt: bool = False, **decode_kwargs):
self.tokenizer = tokenizer
self.skip_prompt = skip_prompt
self.decode_kwargs = decode_kwargs
# variables used in the streaming process
self.token_cache = []
self.print_len = 0
self.next_tokens_are_prompt = True
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def put(self, value):
"""
Receives tokens, decodes them, and prints them to stdout as soon as they form entire words.
"""
if len(value.shape) > 1 and value.shape[0] > 1:
raise ValueError("TextStreamer only supports batch size 1")
elif len(value.shape) > 1:
value = value[0]
if self.skip_prompt and self.next_tokens_are_prompt:
self.next_tokens_are_prompt = False
return
# Add the new token to the cache and decodes the entire thing.
self.token_cache.extend(value.tolist())
text = self.tokenizer.decode(self.token_cache, **self.decode_kwargs)
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# After the symbol for a new line, we flush the cache.
if text.endswith("\n"):
printable_text = text[self.print_len :]
self.token_cache = []
self.print_len = 0
# If the last token is a CJK character, we print the characters.
elif len(text) > 0 and self._is_chinese_char(ord(text[-1])):
printable_text = text[self.print_len :]
self.print_len += len(printable_text)
# Otherwise, prints until the last space char (simple heuristic to avoid printing incomplete words,
# which may change with the subsequent token -- there are probably smarter ways to do this!)
else:
printable_text = text[self.print_len : text.rfind(" ") + 1]
self.print_len += len(printable_text)
self.on_finalized_text(printable_text)
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def end(self):
"""Flushes any remaining cache and prints a newline to stdout."""
# Flush the cache, if it exists
if len(self.token_cache) > 0:
text = self.tokenizer.decode(self.token_cache, **self.decode_kwargs)
printable_text = text[self.print_len :]
self.token_cache = []
self.print_len = 0
else:
printable_text = ""
self.next_tokens_are_prompt = True
self.on_finalized_text(printable_text, stream_end=True)
def on_finalized_text(self, text: str, stream_end: bool = False):
"""Prints the new text to stdout. If the stream is ending, also prints a newline."""
print(text, flush=True, end="" if not stream_end else None)
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def _is_chinese_char(self, cp):
"""Checks whether CP is the codepoint of a CJK character."""
# This defines a "chinese character" as anything in the CJK Unicode block:
# https://en.wikipedia.org/wiki/CJK_Unified_Ideographs_(Unicode_block)
#
# Note that the CJK Unicode block is NOT all Japanese and Korean characters,
# despite its name. The modern Korean Hangul alphabet is a different block,
# as is Japanese Hiragana and Katakana. Those alphabets are used to write
# space-separated words, so they are not treated specially and handled
# like the all of the other languages.
if (
(cp >= 0x4E00 and cp <= 0x9FFF)
or (cp >= 0x3400 and cp <= 0x4DBF) #
or (cp >= 0x20000 and cp <= 0x2A6DF) #
or (cp >= 0x2A700 and cp <= 0x2B73F) #
or (cp >= 0x2B740 and cp <= 0x2B81F) #
or (cp >= 0x2B820 and cp <= 0x2CEAF) #
or (cp >= 0xF900 and cp <= 0xFAFF)
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or (cp >= 0x2F800 and cp <= 0x2FA1F) #
): #
return True
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return False
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class TextIteratorStreamer(TextStreamer):
"""
Streamer that stores print-ready text in a queue, to be used by a downstream application as an iterator. This is
useful for applications that benefit from acessing the generated text in a non-blocking way (e.g. in an interactive
Gradio demo).
<Tip warning={true}>
The API for the streamer classes is still under development and may change in the future.
</Tip>
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Parameters:
tokenizer (`AutoTokenizer`):
The tokenized used to decode the tokens.
skip_prompt (`bool`, *optional*, defaults to `False`):
Whether to skip the prompt to `.generate()` or not. Useful e.g. for chatbots.
timeout (`float`, *optional*):
The timeout for the text queue. If `None`, the queue will block indefinitely. Useful to handle exceptions
in `.generate()`, when it is called in a separate thread.
decode_kwargs (`dict`, *optional*):
Additional keyword arguments to pass to the tokenizer's `decode` method.
Examples:
```python
>>> from transformers import AutoModelForCausalLM, AutoTokenizer, TextIteratorStreamer
>>> from threading import Thread
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>>> tok = AutoTokenizer.from_pretrained("openai-community/gpt2")
>>> model = AutoModelForCausalLM.from_pretrained("openai-community/gpt2")
>>> inputs = tok(["An increasing sequence: one,"], return_tensors="pt")
>>> streamer = TextIteratorStreamer(tok)
>>> # Run the generation in a separate thread, so that we can fetch the generated text in a non-blocking way.
>>> generation_kwargs = dict(inputs, streamer=streamer, max_new_tokens=20)
>>> thread = Thread(target=model.generate, kwargs=generation_kwargs)
>>> thread.start()
>>> generated_text = ""
>>> for new_text in streamer:
... generated_text += new_text
>>> generated_text
'An increasing sequence: one, two, three, four, five, six, seven, eight, nine, ten, eleven,'
```
"""
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def __init__(
self, tokenizer: "AutoTokenizer", skip_prompt: bool = False, timeout: Optional[float] = None, **decode_kwargs
):
super().__init__(tokenizer, skip_prompt, **decode_kwargs)
self.text_queue = Queue()
self.stop_signal = None
self.timeout = timeout
def on_finalized_text(self, text: str, stream_end: bool = False):
"""Put the new text in the queue. If the stream is ending, also put a stop signal in the queue."""
self.text_queue.put(text, timeout=self.timeout)
if stream_end:
self.text_queue.put(self.stop_signal, timeout=self.timeout)
def __iter__(self):
return self
def __next__(self):
value = self.text_queue.get(timeout=self.timeout)
if value == self.stop_signal:
raise StopIteration()
else:
return value
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class AsyncTextIteratorStreamer(TextStreamer):
"""
Streamer that stores print-ready text in a queue, to be used by a downstream application as an async iterator.
This is useful for applications that benefit from acessing the generated text asynchronously (e.g. in an
interactive Gradio demo).
<Tip warning={true}>
The API for the streamer classes is still under development and may change in the future.
</Tip>
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Parameters:
tokenizer (`AutoTokenizer`):
The tokenized used to decode the tokens.
skip_prompt (`bool`, *optional*, defaults to `False`):
Whether to skip the prompt to `.generate()` or not. Useful e.g. for chatbots.
timeout (`float`, *optional*):
The timeout for the text queue. If `None`, the queue will block indefinitely. Useful to handle exceptions
in `.generate()`, when it is called in a separate thread.
decode_kwargs (`dict`, *optional*):
Additional keyword arguments to pass to the tokenizer's `decode` method.
Raises:
TimeoutError: If token generation time exceeds timeout value.
Examples:
```python
>>> from transformers import AutoModelForCausalLM, AutoTokenizer, AsyncTextIteratorStreamer
>>> from threading import Thread
>>> import asyncio
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>>> tok = AutoTokenizer.from_pretrained("openai-community/gpt2")
>>> model = AutoModelForCausalLM.from_pretrained("openai-community/gpt2")
>>> inputs = tok(["An increasing sequence: one,"], return_tensors="pt")
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>>> # Run the generation in a separate thread, so that we can fetch the generated text in a non-blocking way.
>>> async def main():
... # Important: AsyncTextIteratorStreamer must be initialized inside a coroutine!
... streamer = AsyncTextIteratorStreamer(tok)
... generation_kwargs = dict(inputs, streamer=streamer, max_new_tokens=20)
... thread = Thread(target=model.generate, kwargs=generation_kwargs)
... thread.start()
... generated_text = ""
... async for new_text in streamer:
... generated_text += new_text
>>> print(generated_text)
>>> asyncio.run(main())
An increasing sequence: one, two, three, four, five, six, seven, eight, nine, ten, eleven,
```
"""
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def __init__(
self, tokenizer: "AutoTokenizer", skip_prompt: bool = False, timeout: Optional[float] = None, **decode_kwargs
):
super().__init__(tokenizer, skip_prompt, **decode_kwargs)
self.text_queue = asyncio.Queue()
self.stop_signal = None
self.timeout = timeout
self.loop = asyncio.get_running_loop()
self.has_asyncio_timeout = hasattr(asyncio, "timeout")
def on_finalized_text(self, text: str, stream_end: bool = False):
"""Put the new text in the queue. If the stream is ending, also put a stop signal in the queue."""
self.loop.call_soon_threadsafe(self.text_queue.put_nowait, text)
if stream_end:
self.loop.call_soon_threadsafe(self.text_queue.put_nowait, self.stop_signal)
def __aiter__(self):
return self
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async def __anext__(self):
try:
if self.has_asyncio_timeout:
async with asyncio.timeout(self.timeout):
value = await self.text_queue.get()
else:
value = await asyncio.wait_for(self.text_queue.get(), timeout=self.timeout)
except asyncio.TimeoutError:
raise TimeoutError()
else:
if value == self.stop_signal:
raise StopAsyncIteration()
else:
return value
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class GenerateDecoderOnlyOutput(ModelOutput):
"""
Outputs of decoder-only generation models, when using non-beam methods.
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Args:
sequences (`torch.LongTensor` of shape `(batch_size, sequence_length)`):
The generated sequences. The second dimension (sequence_length) is either equal to `max_length` or shorter
if all batches finished early due to the `eos_token_id`.
scores (`tuple(torch.FloatTensor)` *optional*, returned when `output_scores=True`):
Processed prediction scores of the language modeling head (scores for each vocabulary token before SoftMax)
at each generation step. Tuple of `torch.FloatTensor` with up to `max_new_tokens` elements (one element for
each generated token), with each tensor of shape `(batch_size, config.vocab_size)`.
logits (`tuple(torch.FloatTensor)` *optional*, returned when `output_logits=True`):
Unprocessed prediction scores of the language modeling head (scores for each vocabulary token before SoftMax)
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