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Subject: Re: [OMPI users] Issue with Profiling Fortran code
From: Brian W. Barrett (brbarret_at_[hidden])
Date: 2008-12-05 13:06:34


Nick -

I think you have an incorrect deffinition of "correctly" :). According to
the MPI standard, an MPI implementation is free to either layer language
bindings (and only allow profiling at the lowest layer) or not layer the
language bindings (and require profiling libraries intercept each
language). The only requirement is that the implementation document what
it has done.

Since everyone is pretty clear on what Open MPI has done, I don't think
you can claim Open MPI is doing it "incorrectly". Different from MPICH is
not necessarily incorrect. (BTW, LAM/MPI handles profiling the same way
as Open MPI).

Brian

On Fri, 5 Dec 2008, Nick Wright wrote:

> Hi Antony
>
> That will work yes, but its not portable to other MPI's that do implement the
> profiling layer correctly unfortunately.
>
> I guess we will just need to detect that we are using openmpi when our tool
> is configured and add some macros to deal with that accordingly. Is there an
> easy way to do this built into openmpi?
>
> Thanks
>
> Nick.
>
> Anthony Chan wrote:
>> Hope I didn't misunderstand your question. If you implement
>> your profiling library in C where you do your real instrumentation,
>> you don't need to implement the fortran layer, you can simply link
>> with Fortran to C MPI wrapper library -lmpi_f77. i.e.
>>
>> <OMPI>/bin/mpif77 -o foo foo.f -L<OMPI>/lib -lmpi_f77 -lYourProfClib
>>
>> where libYourProfClib.a is your profiling tool written in C. If you don't
>> want to intercept the MPI call twice for fortran program,
>> you need to implment fortran layer. In that case, I would think you
>> can just call C version of PMPI_xxx directly from your fortran layer, e.g.
>>
>> void mpi_comm_rank_(MPI_Comm *comm, int *rank, int *info) {
>> printf("mpi_comm_rank call successfully intercepted\n");
>> *info = PMPI_Comm_rank(comm,rank);
>> }
>>
>> A.Chan
>>
>> ----- "Nick Wright" <nwright_at_[hidden]> wrote:
>>
>>> Hi
>>>
>>> I am trying to use the PMPI interface with OPENMPI to profile a
>>> fortran program.
>>>
>>> I have tried with 1.28 and 1.3rc1 with --enable-mpi-profile switched
>>> on.
>>>
>>> The problem seems to be that if one eg. intercepts to call to
>>> mpi_comm_rank_ (the fortran hook) then calls pmpi_comm_rank_ this then
>>>
>>> calls MPI_Comm_rank (the C hook) not PMPI_Comm_rank as it should.
>>>
>>> So if one wants to create a library that can profile C and Fortran
>>> codes at the same time one ends up intercepting the mpi call twice. Which
>>> is
>>>
>>> not desirable and not what should happen (and indeed doesn't happen in
>>>
>>> other MPI implementations).
>>>
>>> A simple example to illustrate is below. If somebody knows of a fix to
>>>
>>> avoid this issue that would be great !
>>>
>>> Thanks
>>>
>>> Nick.
>>>
>>> pmpi_test.c: mpicc pmpi_test.c -c
>>>
>>> #include<stdio.h>
>>> #include "mpi.h"
>>> void mpi_comm_rank_(MPI_Comm *comm, int *rank, int *info) {
>>> printf("mpi_comm_rank call successfully intercepted\n");
>>> pmpi_comm_rank_(comm,rank,info);
>>> }
>>> int MPI_Comm_rank(MPI_Comm comm, int *rank) {
>>> printf("MPI_comm_rank call successfully intercepted\n");
>>> PMPI_Comm_rank(comm,rank);
>>> }
>>>
>>> hello_mpi.f: mpif77 hello_mpi.f pmpi_test.o
>>>
>>> program hello
>>> implicit none
>>> include 'mpif.h'
>>> integer ierr
>>> integer myid,nprocs
>>> character*24 fdate,host
>>> call MPI_Init( ierr )
>>> myid=0
>>> call mpi_comm_rank(MPI_COMM_WORLD, myid, ierr )
>>> call mpi_comm_size(MPI_COMM_WORLD , nprocs, ierr )
>>> call getenv('HOST',host)
>>> write (*,*) 'Hello World from proc',myid,' out of',nprocs,host
>>> call mpi_finalize(ierr)
>>> end
>>>
>>>
>>>
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