PGIコンパイラを用いてOpenACCを利用

PGIコンパイラを用いてOpenACCを利用してみる (#pragma acc kernels)。以下の例では、ライプニッツの公式を用いて円周率を求め、GCCとPGIコンパイラのそれぞれでかかった時間を書き添えた。

Leibniz_formula_for_pi.c

#include <time.h>
#include <stdio.h>
#include <stdlib.h>

#define N 1600000000L

int main(int argc, char *argv[])
{
  double pi, piq = 1.0;
  long int li, upto = N;
  clock_t begin, end;

  if (argc > 1) upto = atol(argv[1]);

  begin = clock();

#pragma acc kernels
  for (li = 1; li < upto; li++) 
  {
    if (li % 2 == 0) piq += 1.0 / (2.0 * li + 1.0);
    else             piq -= 1.0 / (2.0 * li + 1.0);
  }

  pi = 4.0 * piq;

  end = clock();

  fprintf(stdout, "pi = %.12f (%.2f s)\n",
          pi, (double)(end - begin) / CLOCKS_PER_SEC);
  return EXIT_SUCCESS;
}

$ gcc -v 2>&1 | grep ^gcc
gcc version 5.4.0 20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.5) 
$ gcc -o pi Leibniz_formula_for_pi.c
$ file pi
pi: ELF 64-bit LSB executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked, interpreter /lib64/ld64.so.2, for GNU/Linux 3.2.0, BuildID[sha1]=0133a85d075fb58a5c98988dffd16e3ec6b83a2a, not stripped
$ ./pi 3200000000
pi = 3.141592653276 (27.54 s)
$ which pgcc
/opt/pgi/linuxpower/17.10/bin/pgcc
$ pgcc --version | grep -v ^$
pgcc 17.10-0 linuxpower target on Linuxpower 
PGI Compilers and Tools
Copyright (c) 2017, NVIDIA CORPORATION.  All rights reserved.
$ pgcc -acc -o pi_acc Leibniz_formula_for_pi.c
$ file pi_acc
pi_acc: ELF 64-bit LSB executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked, interpreter /lib64/ld64.so.2, for GNU/Linux 3.2.0, not stripped
$ ./pi_acc 3200000000
pi = 3.141592653276 (14.05 s)