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Source repo: sdsc-summer-institute-2025 | Branch: main | Last synced: 2026-04-24 10:27:17.425 UTC

OpenACC examples

SDSC Summer Institute 2025

Material by Andreas Goetz (agoetz@sdsc.edu) partly based on work by Mark Harris - NVIDIA corporation.

Directory content as explained below.

Vector addition (saxpy)

See subdirectory ./saxpy.

saxpy.c C program that performs single precision vector addition (y = a*x + y).
Can be compiled with standard C compiler or PGI pgcc compiler with accelerator directives.

pgcc saxpy.c -o saxpy-cpu.x pgcc saxpy.c -acc -Minfo=accel -o saxpy-gpu.x

Jacobi solver of 2D Laplace equation

See subdirectory ./laplace-2d.

C and Fortran versions of a Jacobi solver for 2D Laplace equation including OpenMP and OpenACC versions. See below how to compile and benchmarks on SDSC Comet and a pre-Expanse testbed system.

Benchmarks on SDSC Comet node, using K80 GPU​

module load pgi

pgf90 jacobi.f90 -fast -o jacobi-pgf90.x ./jacobi-pgf90.x # completes in 50 seconds

pgcc jacobi.c -fast -o jacobi-pgcc.x ./jacobi-pgcc.x # completes in 71 seconds

pgf90 jacobi-omp.f90 -fast -mp -Minfo=mp -o jacobi-pgf90-omp.x export OMP_NUM_THREADS=2 ./jacobi-pgf90-omp.x # completes in 33 seconds export OMP_NUM_THREADS=4 ./jacobi-pgf90-omp.x # completes in 25 seconds export OMP_NUM_THREADS=6 ./jacobi-pgf90-omp.x # completes in 24 seconds export OMP_NUM_THREADS=12 ./jacobi-pgf90-omp.x # completes in 23 seconds export OMP_NUM_THREADS=24 ./jacobi-pgf90-omp.x # completes in 22 seconds

pgcc jacobi-omp.c -fast -mp -Minfo=mp -o jacobi-pgfcc-omp.x export OMP_NUM_THREADS=2 ./jacobi-pgcc-omp.x # completes in 41 seconds export OMP_NUM_THREADS=4 ./jacobi-pgcc-omp.x # completes in 26 seconds export OMP_NUM_THREADS=6 ./jacobi-pgcc-omp.x # completes in 24 seconds export OMP_NUM_THREADS=12 ./jacobi-pgcc-omp.x # completes in 23 seconds export OMP_NUM_THREADS=24 ./jacobi-pgcc-omp.x # completes in 23 seconds

pgf90 jacobi-acc.f90 -acc -Minfo=accel -o jacobi-pgf90-acc.x ./jacobi-pgf90-acc.x # completes in 5 seconds

pgcc jacobi-acc.c -acc -Minfo=accel -o jacobi-pgcc-acc.x ./jacobi-pgcc-acc.x # completes in 6 seconds

Benchmarks on SDSC V100 test node​

Hardware:

  • 2 x 16-core Intel Xeon Gold 6130 CPU @ 2.10 GHz
  • Nvidia V100-SXM2 GPU

Compile and benchmark:

pgicc --version pgcc 18.10-1 64-bit target on x86-64 Linux -tp skylake

pgf90 jacobi.f90 -fast -o jacobi-pgf90.x ./jacobi-pgf90.x # completes in 44.3 seconds

pgcc jacobi.c -fast -o jacobi-pgcc.x ./jacobi-pgcc.x # completes in 48.2 seconds

pgf90 jacobi-omp.f90 -fast -mp -Minfo=mp -o jacobi-pgf90-omp.x export OMP_NUM_THREADS=2 ./jacobi-pgf90-omp.x # completes in 24 seconds export OMP_NUM_THREADS=4 ./jacobi-pgf90-omp.x # completes in 13 seconds export OMP_NUM_THREADS=8 ./jacobi-pgf90-omp.x # completes in 8 seconds export OMP_NUM_THREADS=16 ./jacobi-pgf90-omp.x # completes in 6 seconds export OMP_NUM_THREADS=32 ./jacobi-pgf90-omp.x # completes in 6 seconds

pgcc jacobi-omp.c -fast -mp -Minfo=mp -o jacobi-pgfcc-omp.x export OMP_NUM_THREADS=2 ./jacobi-pgcc-omp.x # completes in 25 seconds export OMP_NUM_THREADS=4 ./jacobi-pgcc-omp.x # completes in 13 seconds export OMP_NUM_THREADS=6 ./jacobi-pgcc-omp.x # completes in 8 seconds export OMP_NUM_THREADS=12 ./jacobi-pgcc-omp.x # completes in 6 seconds export OMP_NUM_THREADS=24 ./jacobi-pgcc-omp.x # completes in 6 seconds

pgf90 jacobi-acc.f90 -acc -Minfo=accel -o jacobi-pgf90-acc.x ./jacobi-pgf90-acc.x # completes in 1.3 seconds

pgcc jacobi-acc.c -acc -Minfo=accel -o jacobi-pgcc-acc.x ./jacobi-pgcc-acc.x # completes in 1.3 seconds