pithr.c

#include<stdio.h>
#include<omp.h>
static long num_pasos = 100000000;   //1 215 752 192
double paso;
#define NUM_THREADS 500
void main()
{
    int i, nthreads;
    double pi, sum[NUM_THREADS];
    double a = 1.0;
    double b = 2.0;
    paso = (b-a);
    paso = 1.0/num_pasos;
    omp_set_num_threads(NUM_THREADS);
    const double startTime = omp_get_wtime();
    #pragma omp parallel
    {
        int i, id, nthrds; double x;
        id = omp_get_thread_num();
        nthrds = omp_get_num_threads();
        if(id==0)
            nthreads=nthrds;
            for (i=id, sum[id]=0.0; i<num_pasos; i=i+nthrds)
            {
                x=(i+0.5)*paso+1;
                printf("%d\n",i);
                sum[id]+=1.0/(x);
                
            }
            
    }

    for (i=0,pi=0.0;i<nthreads;i++){
        pi+=sum[i]*paso;
    }
    const double endTime = omp_get_wtime();
    printf("threads = %d\n", NUM_THREADS);
    printf("pi = (%lf)\n", pi);
    printf("tomo (%lf) segundos\n", (endTime - startTime));
}