memcpy(tmp_buf, (char *) rbuff + recv_idx * extent, recv_cnt * extent);
mpi_coll_allgather_fun(tmp_buf, recv_cnt, dtype, rbuff, recv_cnt, dtype, comm);
memcpy(tmp_buf, (char *) rbuff + recv_idx * extent, recv_cnt * extent);
mpi_coll_allgather_fun(tmp_buf, recv_cnt, dtype, rbuff, recv_cnt, dtype, comm);