c - MPI_Finalize() 不结束任何进程

Question

我正在使用 openMPI，而且我有一个奇怪的错误。

看来，即使在 MPI_Finalize() 之后，每个线程仍在运行。
我遵循了一个简单的 Hello World 程序的指南，它看起来像这样:

#include <mpi.h>;

int main(int argc, char** argv) {

// Initialize the MPI environment
    MPI_Init(NULL, NULL);

// Get the number of processes
    int world_size;
    MPI_Comm_size(MPI_COMM_WORLD, &world_size);

// Get the rank of the process
    int world_rank;
    MPI_Comm_rank(MPI_COMM_WORLD, &world_rank);

// Get the name of the processor
    char processor_name[MPI_MAX_PROCESSOR_NAME];
    int name_len;
    MPI_Get_processor_name(processor_name, &name_len);

// Print off a hello world message
       printf("Hello world from processor %s, rank %d"
       " out of %d processors\n",
       processor_name, world_rank, world_size);

// Finalize the MPI environment.
    MPI_Finalize();

    printf("This is after finalize");
}

注意最后一个 printf()... 这应该只打印一次，因为并行部分已经完成，对吧？!

但是，例如，如果我使用 6 个处理器运行该程序，则该程序的输出是:

mpirun -np 6 ./hello_world

Hello world from processor ubuntu, rank 2 out of 6 processors
Hello world from processor ubuntu, rank 1 out of 6 processors
Hello world from processor ubuntu, rank 3 out of 6 processors
Hello world from processor ubuntu, rank 0 out of 6 processors
Hello world from processor ubuntu, rank 4 out of 6 processors
Hello world from processor ubuntu, rank 5 out of 6 processors
This is after finalize...
This is after finalize...
This is after finalize...
This is after finalize...
This is after finalize...
This is after finalize...

我误解了 MPI 的工作原理吗？每个线程/进程不应该被 finalize 停止吗？

Answer 1

这只是未定义的行为。

The number of processes running after this routine is called is undefined; it is best not to perform much more than a return rc after calling MPI_Finalize.

http://www.mpich.org/static/docs/v3.1/www3/MPI_Finalize.html