recv_offset = rank * block_size;
Datatype::copy(send_buff, send_count, send_type, (char *)recv_buff + recv_offset,
recv_count, recv_type);
recv_offset = rank * block_size;
Datatype::copy(send_buff, send_count, send_type, (char *)recv_buff + recv_offset,
recv_count, recv_type);