My solution to: http://www.hpc.cineca.it/content/exercise-3

ex3.c

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

#define SIZE 10000

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

    MPI_Request request;
    MPI_Status status;

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

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

    left = (rank == 0) ? size - 1 : rank - 1;
    right = (rank == size - 1) ? 0 : rank + 1;
    MPI_Isend(A, SIZE, MPI_INT, right, 0, MPI_COMM_WORLD, &request);
    MPI_Recv(B, SIZE, MPI_INT, left, 0, MPI_COMM_WORLD, &status);
    printf("I am task %d and I have received B[0] = %d.00\n", rank, B[0]);

    MPI_Finalize();
    return 0;
}