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Subject: Re: [OMPI users] Issue with Profiling Fortran code
From: Anthony Chan (chan_at_[hidden])
Date: 2008-12-05 18:58:57


Hi Nick,

----- "Nick Wright" <nwright_at_[hidden]> wrote:

> For the first case you describe, as OPENMPI is now, the call sequence
>
> from fortran is
>
> mpi_comm_rank -> MPI_Comm_rank -> PMPI_Comm_rank
>
> For the second case, as MPICH is now, its
>
> mpi_comm_rank -> PMPI_Comm_rank
>

AFAIK, all known/popular MPI implemention's fortran binding
layer is implemented with C MPI functions, including
MPICH2 and OpenMPI. If MPICH2's fortran layer was implemented
the way you said, typical profiling tools including MPE will
fail to work with fortran applications.

e.g. check mpich2-xxx/src/binding/f77/sendf.c.

A.Chan

> So for the first case if I have a pure fortran/C++ code I have to
> profile at the C interface.
>
> So is the patch now retracted ?
>
> 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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> >>
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