2.1.2 prime_omp.c のソースコード

prime_omp.c のソースコードは次に示すとおりです。

  1  /*
  2   * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All Rights Reserved.
  3   * @(#)prime_omp.c 1.3 (Oracle) 10/03/26
  4   */
  5
  6  #include <stdio.h>
  7  #include <math.h>
  8  #include <omp.h>
  9
 10  #define THREADS 4
 11  #define N 10000
 12
 13  int primes[N];
 14  int pflag[N];
 15
 16  int is_prime(int v)
 17  {
 18   int i;
 19   int bound = floor(sqrt(v)) + 1;
 20
 21   for (i = 2; i < bound; i++) {
 22          /* no need to check against known composites */
 23          if (!pflag[i])
 24              continue;
 25          if (v % i == 0) {
 26              pflag[v] = 0;
 27              return 0;
 28          }
 29      }
 30      return (v > 1);
 31  }
 32
 33  int main(int argn, char **argv)
 34  {
 35      int i;
 36      int total = 0;
 37
 38  #ifdef _OPENMP
 39      omp_set_dynamic(0);
 40      omp_set_num_threads(THREADS);
 41  #endif
 42
 43      for (i = 0; i < N; i++) {
 44          pflag[i] = 1;
 45      }
 46
 47      #pragma omp parallel for
 48      for (i = 2; i < N; i++) {
 49          if ( is_prime(i) ) {
 50              primes[total] = i;
 51              total++;
 52          }
 53      }
 54
 55      printf("Number of prime numbers between 2 and %d: %d\n",
 56             N, total);
 57
 58      return 0;
 59  }