Computing p with Shared Memory

• Notes:

  • essentially sequential form
  • automatic work sharing
  • all variables shared by default
  • directives to request parallel work distribution
  • number of processors specified outside of the code

#define n 1000000

main() {

double pi, l, ls = 0.0, w = 1.0/n;

int i;

#pragma omp parallel private(i,l) reduction(+:ls)

{

#pragma omp for

for(i=0; i<n; i++) {

l = (i+0.5)*w;

ls += 4.0/(1.0+l*l);

}

#pragma omp master

printf(“pi is %f\n”,ls*w);

#pragma omp end master

}

}

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