err = MPI_Pack_size(type_size/sizeof(int), MPI_INT, MPI_COMM_SELF, &pack_size);
check_err(MPI_Pack_size);
pack_buf = malloc(pack_size);
err = MPI_Pack_size(type_size/sizeof(int), MPI_INT, MPI_COMM_SELF, &pack_size);
check_err(MPI_Pack_size);
pack_buf = malloc(pack_size);