Question

我遇到的问题类似于所讨论的问题in this topic，我有一个MPI代码，它对具有特定行数的向量的行求和。我附上the code here。

当我尝试使用一个核心在线编译mpirun -n 1 ./program时，我获得了：

500000 sum 125000250000.00000 calculated by root process. The grand total is: 125000250000.00000 因为我只有一个计算总和的核心，所以看起来还不错。但是当我尝试使用多核mpirun -n 4 ./program时，我获得了：

please enter the number of numbers to sum:
500000
[federico-C660:9540] *** An error occurred in MPI_Recv
[federico-C660:9540] *** on communicator MPI_COMM_WORLD
[federico-C660:9540] *** MPI_ERR_TRUNCATE: message truncated
[federico-C660:9540] *** MPI_ERRORS_ARE_FATAL (your MPI job will now abort)
 sum    7812562500.0000000       calculated by root process.
--------------------------------------------------------------------------
mpirun has exited due to process rank 1 with PID 9539 on
node XXXXX1 exiting without calling "finalize".

我也为C程序here提出了类似的问题。与2和3处理器相同。

有人可以帮我弄清问题是什么？我的猜测是我在与＃34;发送者＆＃34;相关的MPI_RECV呼叫中犯了一个错误。

Answer 1

代码中存在一些问题;

最明显的问题是接收变量 num_rows_to_receive 的语法错误。您已收到 num_rows_to_received 中root_process计算的行，但使用变量 num_rows_to_receive 实际接收向量。 CALL mpi_recv (num_rows_to_receive, 1 , mpi_integer, root_process, mpi_any_tag, mpi_comm_world, STATUS, ierr) CALL mpi_recv (vector2, num_rows_to_receive, mpi_real8, root_process, mpi_any_tag, mpi_comm_world, STATUS, ierr)

这应解决错误。

第二个问题（至少我可以在我的系统上看到）是MPI_REAL数据类型默认为MPI_REAL4并且向量的大小被截断。因此，我们无法获得所有元素的实际总和。将mpi_real更改为MPI_REAL8将修复求和问题，您可以获得所有任意数量的等级的确切求和值。 ~/temp$ mpirun -n 8 ./a.out please enter the number of numbers to sum: 500000 sum 1953156250.0000000 calculated by root process. partial sum 5859406250.0000000 returned from process 1 partial sum 9765656250.0000000 returned from process 2 partial sum 17578156250.000000 returned from process 4 partial sum 21484406250.000000 returned from process 5 partial sum 13671906250.000000 returned from process 3 partial sum 25390656250.000000 returned from process 6 partial sum 29296906250.000000 returned from process 7 The grand total is: 125000250000.00000

`MPI_ERR_TRUNCATE：消息截断'错误

1 个答案: