if(status!=MPI_ERR_BUFFER)
printf("MPI_Allgatherv did not return MPI_ERR_BUFFER for empty recvbuf\n");
status = MPI_Allgatherv(sb, recv_counts[rank], MPI_INT, rb, NULL, recv_disps, MPI_INT, MPI_COMM_WORLD);
if(status!=MPI_ERR_BUFFER)
printf("MPI_Allgatherv did not return MPI_ERR_BUFFER for empty recvbuf\n");
status = MPI_Allgatherv(sb, recv_counts[rank], MPI_INT, rb, NULL, recv_disps, MPI_INT, MPI_COMM_WORLD);