Using MPI_Irecv and MPI_Test


#include "mpi.h"
#include <stdio.h>

int main(int argc, char *argv[])
{
    int rank, numprocs, i, flag=0,working=0;
    int buffer[2]={1,2}, buffer2[2]={3,4}, buffer3[2]={5,6};
    MPI_Request request;
    MPI_Status status;
    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    if (rank==0) {
        MPI_Irecv(buffer, 2, MPI_INT, 1, 123, MPI_COMM_WORLD, &request);
        printf("0 buffer[0]=%i\n",buffer[0]);
        MPI_Send(buffer3, 2, MPI_INT, 1, 1234, MPI_COMM_WORLD);
        MPI_Test(&request, &flag, &status);
        while (!flag) {
            working=0;
            for (i=0;i<100000;i++)working++;
            printf("still testing\n");
            MPI_Test(&request, &flag, &status);
        }
        printf("0 buffer[0]=%i\n",buffer[0]);
    } else {
        printf("1 buffer[0]=%i\n",buffer[0]);
        MPI_Recv(buffer, 2, MPI_INT, 0, 1234, MPI_COMM_WORLD,MPI_STATUS_IGNORE);
        printf("1 buffer[0]=%i\n",buffer[0]);
        MPI_Send(buffer2, 2, MPI_INT, 0, 123, MPI_COMM_WORLD);
    }

    MPI_Finalize();
    return 0;
}