drd/tests/omp_prime.c

   1 /** An OpenMP example.
   2  *  Based on the example listed on the following web page:
   3  *  http://developers.sun.com/sunstudio/downloads/ssx/tha/tha_using.html
   4  */
   5
   6
   7 #include <assert.h>
   8 #include <math.h>
   9 #include <omp.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <unistd.h>  // getopt()
  13 #include "../../drd/drd.h"
  14
  15
  16 static int is_prime(int* const pflag, int v)
  17 {
  18   int i;
  19   int bound = floor(sqrt ((double)v)) + 1;
  20
  21   for (i = 2; i < bound; i++)
  22   {
  23     /* No need to check against known composites */
  24     if (!pflag[i])
  25       continue;
  26     if (v % i == 0)
  27     {
  28       pflag[v] = 0;
  29       return 0;
  30     }
  31   }
  32   return (v > 1);
  33 }
  34
  35 int main(int argc, char **argv)
  36 {
  37   int i;
  38   int total = 0;
  39   int trace_total = 0;
  40   int silent = 0;
  41   int n;
  42   int num_threads = 2;
  43   int optchar;
  44   int* primes;
  45   int* pflag;
  46
  47   while ((optchar = getopt(argc, argv, "qt:v")) != EOF)
  48   {
  49     switch (optchar)
  50     {
  51     case 'q':
  52       silent = 1;
  53       break;
  54     case 't':
  55       num_threads = atoi(optarg);
  56       break;
  57     case 'v':
  58       trace_total = 1;
  59       break;
  60     default:
  61       fprintf(stderr, "Error: unknown option '%c'.\n", optchar);
  62       return 1;
  63     }
  64   }
  65
  66   if (optind + 1 != argc)
  67   {
  68     fprintf(stderr, "Error: wrong number of arguments.\n");
  69     return 1;
  70   }
  71   n = atoi(argv[optind]);
  72
  73   // Not the most user-friendly way to do error checking, but better than
  74   // nothing.
  75   assert(n > 2);
  76   assert(num_threads >= 1);
  77
  78   primes = malloc(n * sizeof(primes[0]));
  79   pflag  = malloc(n * sizeof(pflag[0]));
  80
  81   omp_set_num_threads(num_threads);
  82   omp_set_dynamic(0);
  83
  84   for (i = 0; i < n; i++) {
  85     pflag[i] = 1;
  86   }
  87
  88   if (trace_total)
  89     DRD_TRACE_VAR(total);
  90
  91 #pragma omp parallel for
  92   for (i = 2; i < n; i++)
  93   {
  94     if (is_prime(pflag, i))
  95     {
  96       primes[total] = i;
  97       total++;
  98     }
  99   }
 100   if (! silent)
 101   {
 102     printf("Number of prime numbers between 2 and %d: %d\n",
 103            n, total);
 104     for (i = 0; i < total; i++)
 105     {
 106       printf("%d\n", primes[i]);
 107     }
 108   }
 109
 110   free(pflag);
 111   free(primes);
 112
 113   return 0;
 114 }