PI open MP : approche SPMD
#include <omp.h>
static long etapes = 100000; double pas;
#define NB_THREADS 2
void main ()
{ int i; double x, pi, sum[NB_THREADS];
pas = 1.0/(double) etapes;
omp_set_num_threads(NB_THREADS)
#pragma omp parallel
{ double x; int id;
id = omp_get_thread_num();
for (i=id, sum[id]=0.0;i< etapes; i=i+NB_THREADS){
x = ((double)i+0.5)*pas;
sum[id] += 4.0/(1.0+x*x);
}
}
for(i=0, pi=0.0;i<NB_THREADS;i++)
pi += sum[i] * pas;
}

Program PI OpenMP: Work sharing construct
#include <omp.h>
static long etapes = 100000; double pas;
#define NB_THREADS 2
void main ()
{ int i; double x, pi, sum[NB_THREADS];
pas = 1.0/(double) etapes;
omp_set_num_threads(NB_THREADS)
#pragma omp parallel
{ double x; int id;
id = omp_get_thread_num(); sum[id] = 0;
#pragma omp for
for (i=0;i< etapes; i++){
x = ((double)i+0.5)*pas;
sum[id] += 4.0/(1.0+x*x);
}
} for(i=0, pi=0.0;i<NB_THREADS;i++)
pi += sum[i] * pas;
}

Programme PI OpenMP: clause privée et section critique
#include <omp.h>
static long etapes = 100000; double pas;
#define NB_THREADS 2
void main ()
{ int i; double x, sum, pi=0.0;
pas = 1.0/(double) etapes;
omp_set_num_threads(NB_THREADS)
#pragma omp parallel private (x, sum)
{
id = omp_get_thread_num();
for (i=id,sum=0.0;i< etapes;i=i+NB_THREADS){
x = ((double)i+0.5)*pas;
sum += 4.0/(1.0+x*x);
}
#pragma omp critical
pi += sum
}

Programme PI OpenMP : For parallèle + réduction
#include <omp.h>
static long etapes = 100000; double pas;
#define NB_THREADS 2
void main ()
{ int i; double x, pi, sum = 0.0;
pas = 1.0/(double) etapes;
omp_set_num_threads(NB_THREADS)
#pragma omp parallel for reduction(+:sum) private(x)
for (i=1;i<= etapes; i++){
x = ((double)i-0.5)*pas;
sum = sum + 4.0/(1.0+x*x);
}
pi = pas * sum;
}