Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quasi-Dynamic Traffic Assignment using High Performance Computing   Traffic assignment methods are some of the key approaches used to model flow
patterns that arise in transportation networks. Since static traffic assignment
does not have a notion of time, it is not designed to represent temporal
dynamics that arise as vehicles flow through the network and demand varies
through the day. Dynamic traffic assignment methods attempt to resolve these
issues, but require significant computational resources if modeling urban-scale
regions (on the order of millions of links and vehicles) and often take days of
compute time to complete. The focus of this work is two-fold: 1) to introduce a
new traffic assignment approach - a quasi-dynamic traffic assignment (QDTA)
model and 2) to describe how we parallelized the QDTA algorithms to leverage
High-Performance Computing (HPC) and scale to large metropolitan areas while
dramatically reducing compute time. We examine and compare different scenarios,
including a baseline static traffic assignment (STA) and a quasi-dynamic
scenario inspired by the user-equilibrium (UET). Results are presented for the
San Francisco Bay Area which accounts for 19M trips/day and an urban road
network of 1M links. We utilize an iterative gradient descent method, where the
step size is selected using a Quasi-Newton method with parallelized cost
function evaluations and compare it to using pre-defined step sizes (MSA).
Using the parallelized line search provides a 16 percent reduction in total
execution time due to a reduction in the number of gradient descent iterations
required for convergence. The full day QDTA comprising 96 optimization steps
over 15 minute intervals runs in about 4 minutes on 1,024 cores of the NERSC
Cori computer, which represents a speedup of over 36x versus serial execution.
To our knowledge, this compute time is significantly lower than other traffic
assignment solutions for a problem of this scale.

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The categories of this paper are: cond-mat
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
16
The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ex