My solution to: http://www.hpc.cineca.it/content/exercise-2-0

ex2.c

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

#define SIZE 10000

int main (int argc, char** argv) {
    int i, rank;
    int A[SIZE], B[SIZE];

    MPI_Status s1, s2;

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);

    for (i = 0; i < SIZE; i++) {
        A[i] = rank;
    }

    if (rank == 0) {
        MPI_Send(A, SIZE, MPI_INT, 1, 0, MPI_COMM_WORLD);
        MPI_Recv(B, SIZE, MPI_INT, 1, 1, MPI_COMM_WORLD, &s1);
    } else if (rank == 1) {
        MPI_Recv(B, SIZE, MPI_INT, 0, 0, MPI_COMM_WORLD, &s2);
        MPI_Send(A, SIZE, MPI_INT, 0, 1, MPI_COMM_WORLD);
    }

    // For some reason, the expected output appends ".00" to integers.
    printf("I am task %d and I have received B[0] = %d.00\n", rank, B[0]);

    MPI_Finalize();

    return 0;
}