Creation of a contiguous type in MPI

mpi_contiguous.cpp

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

int main(int argc, char* argv[])
{
    MPI_Init(&argc, &argv);

    int size;
    MPI_Comm_size(MPI_COMM_WORLD, &size);

    int my_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);

    MPI_Datatype MPI_MEGABYTE_TYPE;
    int mega = 1 << 20;
    MPI_Type_contiguous(mega, MPI_BYTE, &MPI_MEGABYTE_TYPE);
    MPI_Type_commit(&MPI_MEGABYTE_TYPE);

    int count = 4;
    size_t length = mega * count;
    char buffer[mega * count];
    if(my_rank == 0) {
        for(size_t i = 0; i < length; i++) {
            buffer[i] = 'l';
        }
        MPI_Send(&buffer, count, MPI_MEGABYTE_TYPE, 1, 0, MPI_COMM_WORLD);
    } else {
        MPI_Recv(&buffer, count, MPI_MEGABYTE_TYPE, 0, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
        printf("%c\n", buffer[length-1]);
    }

    MPI_Finalize();

    return 0;
}