Question

我的代码有效：

program main
implicit none
    include "mpif.h"

    integer :: root, rank, err, status(MPI_STATUS_SIZE)
    integer :: n, m

    call MPI_INIT(err)
    call MPI_COMM_RANK(MPI_COMM_WORLD, rank, err)


    root = 0

    if (rank == root) then
        m = 1
        n = 2
    end if

    call MPI_BCAST(m, 1, MPI_INTEGER, root, MPI_COMM_WORLD, err)
    call MPI_BCAST(n, 1, MPI_INTEGER, root, MPI_COMM_WORLD, err)

    print*, 'Rank ', rank, ' received m=', m,' and n=', n

    call MPI_FINALIZE(err)

end program

我得到预期的输出：

 Rank            0  received m=           1  and n=           2
 Rank            1  received m=           1  and n=           2
 Rank            2  received m=           1  and n=           2
 Rank            3  received m=           1  and n=           2

但是现在，如果我将MPI_BCAST中的一个放在if语句中：

program main
implicit none
    include "mpif.h"

    integer :: root, rank, err, status(MPI_STATUS_SIZE)
    integer :: n, m

    call MPI_INIT(err)
    call MPI_COMM_RANK(MPI_COMM_WORLD, rank, err)


    root = 0

    if (rank == root) then
        m = 1
        n = 2
        call MPI_BCAST(m, 1, MPI_INTEGER, root, MPI_COMM_WORLD, err)
    end if

    call MPI_BCAST(n, 1, MPI_INTEGER, root, MPI_COMM_WORLD, err)

    print*, 'Rank ', rank, ' received m=', m,' and n=', n

    call MPI_FINALIZE(err)

end program

输出不是我所期望的：

 Rank            0  received m=           1  and n=           2
 Rank            1  received m=           0  and n=           1
 Rank            2  received m=           0  and n=           1
 Rank            3  received m=           0  and n=           1

据我所知，通过将第一个MPI_BCAST置于if语句中，其余的不等待并且没有收到消息。但为什么这也打破了第二个MPI_BCAST呢？其他流程不应该在第二个root

等待MPI_BCAST

两个MPI_BCAST，一个在if语句中，一个在

0 个答案: