C example

• #include "mpi.h"

• #include <stdio.h>

• #include <stdlib.h>

• int main(int argc,char *argv[])

• {

• int n=1000000, myid, np, i;

• double sum, pi, h;

• char host[MPI_MAX_PROCESSOR_NAME];

• MPI_Init(&argc,&argv);

• MPI_Comm_size(MPI_COMM_WORLD,&np);

• MPI_Comm_rank(MPI_COMM_WORLD,&myid);

• MPI_Get_processor_name(host,&n);

• fprintf(stderr,"Process %d on %s\n", myid, host);

• MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);

• h = 1.0 / n;

• sum = 0;

• for (i=myid+1; i<=n; i+=np)

• {

• double x = h*(i-0.5);

• sum += 4/(1+x*x);

• }

• sum *= h;

• MPI_Reduce(&sum , &pi , 1 , MPI_DOUBLE , MPI_SUM , 0 , MPI_COMM_WORLD);

• if (myid == 0) printf("pi =%.16f, error=%.16f\n", pi, pi -3.141592653589793238462643);

• MPI_Finalize();

• return 0;

• }

• See Appendix C for a more complete example

Notes: