Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Multi-GPU Performance Optimization of a CFD Code using OpenACC on
  Different Platforms   This paper investigates the multi-GPU performance of a 3D buoyancy driven
cavity solver using MPI and OpenACC directives on different platforms. The
paper shows that decomposing the total problem in different dimensions affects
the strong scaling performance significantly for the GPU. Without proper
performance optimizations, it is shown that 1D domain decomposition scales
poorly on multiple GPUs due to the noncontiguous memory access. The performance
using whatever decompositions can be benefited from a series of performance
optimizations in the paper. Since the buoyancy driven cavity code is
latency-bounded on the clusters examined, a series of optimizations both
agnostic and tailored to the platforms are designed to reduce the latency cost
and improve memory throughput between hosts and devices efficiently. First, the
parallel message packing/unpacking strategy developed for noncontiguous data
movement between hosts and devices improves the overall performance by about a
factor of 2. Second, transferring different data based on the stencil sizes for
different variables further reduces the communication overhead. These two
optimizations are general enough to be beneficial to stencil computations
having ghost changes on all of the clusters tested. Third, GPUDirect is used to
improve the communication on clusters which have the hardware and software
support for direct communication between GPUs without staging CPU's memory.
Finally, overlapping the communication and computations is shown to be not
efficient on multi-GPUs if only using MPI or MPI+OpenACC. Although we believe
our implementation has revealed enough overlap, the actual running does not
utilize the overlap well due to a lack of asynchronous progression.

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The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
11
The categories of this paper are: hep-lat
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: ao-sci
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn