c – Openmpi mpmd获取通信大小

我有两个openmpi程序,我这样开始

mpirun -n 4 ./prog1 : -n 2 ./prog2

现在我如何使用MPI_Comm_size(MPI_COMM_WORLD,& size)使得我得到大小值为

prog1 size=4
prog2 size=2.

到目前为止,我在两个节目中都获得了“6”.

解决方法:

这是可行的,尽管有点麻烦.原则是根据argv [0]的值将MPI_COMM_WORLD拆分为通信器,其中包含可执行文件的名称.

那可能是这样的：

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <mpi.h>

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

    MPI_Init( &argc, &argv );

    int wRank, wSize;
    MPI_Comm_rank( MPI_COMM_WORLD, &wRank );
    MPI_Comm_size( MPI_COMM_WORLD, &wSize );

    int myLen = strlen( argv[0] ) + 1;
    int maxLen;
    // Gathering the maximum length of the executable' name
    MPI_Allreduce( &myLen, &maxLen, 1, MPI_INT, MPI_MAX, MPI_COMM_WORLD );

    // Allocating memory for all of them
    char *names = malloc( wSize * maxLen );
    // and copying my name at its place in the array
    strcpy( names + ( wRank * maxLen ), argv[0] );

    // Now collecting all executable' names
    MPI_Allgather( MPI_IN_PLACE, 0, MPI_DATATYPE_NULL,
                   names, maxLen, MPI_CHAR, MPI_COMM_WORLD );

    // With that, I can sort-out who is executing the same binary as me
    int binIdx = 0;
    while( strcmp( argv[0], names + binIdx * maxLen ) != 0 ) {
        binIdx++;
    }
    free( names );

    // Now, all processes with the same binIdx value are running the same binary
    // I can split MPI_COMM_WORLD accordingly
    MPI_Comm binComm;
    MPI_Comm_split( MPI_COMM_WORLD, binIdx, wRank, &binComm );

    int bRank, bSize;
    MPI_Comm_rank( binComm, &bRank );
    MPI_Comm_size( binComm, &bSize );

    printf( "Hello from process WORLD %d/%d running %d/%d %s binary\n",
            wRank, wSize, bRank, bSize, argv[0] );

    MPI_Comm_free( &binComm );

    MPI_Finalize();

    return 0;
}

在我的机器上,我编译并运行如下：

~> mpicc mpmd.c
~> cp a.out b.out
~> mpirun -n 3 ./a.out : -n 2 ./b.out
Hello from process WORLD 0/5 running 0/3 ./a.out binary
Hello from process WORLD 1/5 running 1/3 ./a.out binary
Hello from process WORLD 4/5 running 1/2 ./b.out binary
Hello from process WORLD 2/5 running 2/3 ./a.out binary
Hello from process WORLD 3/5 running 0/2 ./b.out binary

理想情况下,如果存在用于通过二进制文件排序的相应类型,则可以通过使用MPI_Comm_split_type()来大大简化此操作.不幸的是,3.1 MPI标准中没有预先定义的MPI_COMM_TYPE_.唯一预定义的是MPI_COMM_TYPE_SHARED,用于在同一共享内存计算节点上运行的进程之间进行排序……太糟糕了！对于下一版本的标准,可能需要考虑一些事项？

标签：c-3,openmpi,c,parallel-processing,mpi
来源： https://codeday.me/bug/20190927/1824556.html