2.1.1 Complete Listing of omp_prime.c

1   #include <stdio.h>
2   #include <math.h>
3   #include <omp.h>
4
5   #define THREADS 4
6   #define N 3000
7
8   int primes[N];
9   int pflag[N];
10
11  int is_prime(int v)
12  {
13      int i;
14      int bound = floor(sqrt ((double)v)) + 1;
15      
16      for (i = 2; i < bound; i++) {
17          /* No need to check against known composites */ 
18          if (!pflag[i]) 
19              continue;
20          if (v % i == 0) { 
21              pflag[v] = 0;
22              return 0;
23          }
24      }
25      return (v > 1); 
26  }
27
28  int main(int argn, char **argv)
29  {
30      int i;
31      int total = 0;
32
33  #ifdef _OPENMP
34      omp_set_num_threads(THREADS);
35      omp_set_dynamic(0);
36  #endif
37
38      for (i = 0; i < N; i++) {
39          pflag[i] = 1; 
40      }
41      
42      #pragma omp parallel for
43      for (i = 2; i < N; i++) {
44          if ( is_prime(i) ) {
45              primes[total] = i;
46              total++;
47          }
48      }
49      printf("Number of prime numbers between 2 and %d: %d\n",
50             N, total);
51      for (i = 0; i < total; i++) {
52          printf("%d\n", primes[i]);
53      }
54
55  return 0;
56  }