int number;
MPI_Status status;
MPI_Request in_request = MPI_REQUEST_NULL;
if (world_rank == 0) {
    number = -1;
    MPI_IBcast(&number, 1, MPI_INT, 0, MPI_COMM_WORLD);
} else {
    MPI_IRecv(&number, 1, MPI_INT, 0, 0, MPI_COMM_WORLD,MPI_STATUS_IGNORE);
}
MPI_Wait(&request, &status);