MPI_COMM_WORLD 句柄在子例程中丢失值

发布于 2024-09-28 14:24:26 字数 916 浏览 5 评论 0原文

我的程序如下：
模块x
使用 mpi !x 包含 mpi 模块
隐式无
...
包含

subroutine do_something_with_mpicommworld  

    !use mpi !uncommenting this makes a difference (****)  
    call MPI_...(MPI_COMM_WORLD,...,ierr)  

end subroutine

...
结束模块 x

程序主
使用 mpi 使用x
MPI_INIT(...)
调用 do_something_with_mpicommworld end program main

此程序失败并出现以下错误： MPI_Cart_create(199): 无效的通信器，除非标有 (**) 的行未注释。

现在，也许我对 Fortran 90 的了解还不完整，但我想如果你在模块定义中有一个 use 子句（请参阅我的模块 x），则无论包含的模块中存在哪个全局变量（如果是x : 来自包含模块 mpi 的 MPI_COMM_WORLD 将在任何包含的子例程 ( do_something_with_mpicommworld ) 中具有相同的值，即使这些子例程未显式包含该模块（例如，当 (**) 被注释掉时）。或者，简单地说，如果您在另一个模块中包含一个模块，则第二个模块中包含的子例程将可以访问所包含模块中的全局变量，而无需特殊的 use 语句。

当我运行程序时，我看到了不同的行为。 x 中包含的 sub 会产生错误，除非它具有“use mpi”语句。

那么问题出在哪里，我对 Fortran 90 的看法是否错误，或者 MPI 模块有什么特殊之处会导致这种行为吗？

原文

my program is as follows:
module x
use mpi !x includes mpi module
implicit none
...
contains

subroutine do_something_with_mpicommworld  

    !use mpi !uncommenting this makes a difference (****)  
    call MPI_...(MPI_COMM_WORLD,...,ierr)  

end subroutine

...
end module x

program main
use mpi
use x
MPI_INIT(...)
call do_something_with_mpicommworld
end program main

This program fails with the following error: MPI_Cart_create(199): Invalid communicator, unless
the line marked with (**) is uncommented.

Now, maybe my knowledge of Fortran 90 is incomplete, but i thought if you have a use clause in the module definition (see my module x), whichever global variable exists in the included module (in case of x : MPI_COMM_WORLD from include module mpi) will have the same value in any of the contained subroutines ( do_something_with_mpicommworld ) even when those subroutines do not explicitly include the module (e.g. when (**) is commented out). Or, to put it simply, if you include a module within another module, the subroutines contained in the second module will have access to the globals in the included module without a special use statement.

When I ran my programme, I saw a different behaviour. The sub contained in x was creating errors unless it had the 'use mpi' statement.

So what is the problem, do I have a wrong idea about Fortran 90, or is there something special about MPI module which induces such behaviour?

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墨落画卷 2024-10-05 14:24:26

令人烦恼的是，很难找到关于这些情况下应该发生什么和不应该发生什么的确切细节，我的期望与你的相同——“使用 mpi”应该像上面那样工作。所以我尝试了以下方法：

module hellompi
use mpi
implicit none
contains

subroutine hello
    integer :: ierr, nprocs, rank
    call MPI_INIT(ierr)
    call MPI_COMM_SIZE(MPI_COMM_WORLD, nprocs, ierr)
    call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
    print *, 'Hello world, from ', rank, ' of ', nprocs
    print *, MPI_COMM_WORLD
    call MPI_FINALIZE(ierr)
    return
end subroutine hello

end module hellompi

它在带有 OpenMPI 的 gfortran 和 ifort 下运行良好。添加 cart_create 不会改变任何东西。

让我觉得奇怪的是，你的情况并没有抱怨 MPI_COMM_WORLD 没有定义——所以显然一些相关信息正在被传播到子例程。您能否发布一个更简单的完整示例，但仍然无法正常工作？

Its annoyingly hard to find exact details about what should and shouldn't happen in these cases, and my expectation was the same as yours -- the `use mpi' should work as above. So I tried the following:

module hellompi
use mpi
implicit none
contains

subroutine hello
    integer :: ierr, nprocs, rank
    call MPI_INIT(ierr)
    call MPI_COMM_SIZE(MPI_COMM_WORLD, nprocs, ierr)
    call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)
    print *, 'Hello world, from ', rank, ' of ', nprocs
    print *, MPI_COMM_WORLD
    call MPI_FINALIZE(ierr)
    return
end subroutine hello

end module hellompi

and it works fine under both gfortran and ifort with OpenMPI. Adding a cart_create doesn't change anything.

What strikes me as weird with your case is that it isn't complaining that MPI_COMM_WORLD isn't defined -- so obviously some of the relevant information is being propagated to the subroutine. Can you post a simpler full example which still fails to work?

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