From MPI to MPI+OpenACC: Conversion of a legacy FORTRAN PCG solver for the spherical Laplace equation
Predictive Science Inc., 9990 Mesa Rim Road Suite 170, San Diego, CA 92121
arXiv:1709.01126 [cs.MS], (4 Sep 2017)
@article{caplan2017from,
title={From MPI to MPI+OpenACC: Conversion of a legacy FORTRAN PCG solver for the spherical Laplace equation},
author={Caplan, Ronald M. and Mikic, Zoran and Linker, Jon A.},
year={2017},
month={sep},
archivePrefix={"arXiv"},
primaryClass={cs.MS}
}
A real-world example of adding OpenACC to a legacy MPI FORTRAN Preconditioned Conjugate Gradient code is described, and timing results for multi-node multi-GPU runs are shown. The code is used to obtain three-dimensional spherical solutions to the Laplace equation. Its application is finding potential field solutions of the solar corona, a useful tool in space weather modeling. We highlight key tips, strategies, and challenges faced when adding OpenACC, including linking FORTRAN code to the cuSparse library, using CUDA-aware MPI, maintaining portability, and dealing with multi-node, multi-GPU run-time environments. Timing results are shown for the code running with MPI-only (up to 1728 CPU cores) and with MPI+OpenACC (up to 64 NVIDIA P100 GPUs). Performance portability is also addressed, including results using MPI+OpenACC for multi-core x86 CPUs.
September 7, 2017 by hgpu
