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Subject: Re: [OMPI users] bug in mpif90? OMPI_FC envvar does not work with 'use mpi'
From: Iliev, Hristo (Iliev_at_[hidden])
Date: 2013-03-13 04:58:34


Hi, Dominik,

gfortran and ifort produce Fortran module files (*.mod) with completely
different and hence incompatible formats. You cannot use a module compiled
with gfortran in ifort and vice versa. That's why many Fortran libraries
come with explicit module interface definitions that have to be compiled
with the specific Fortran compiler before the library can be used as a
module.

Hope that helps to clarify the issue.

Kind regards,
Hristo

--
Hristo Iliev, PhD – High Performance Computing Team
RWTH Aachen University, Center for Computing and Communication
Rechen- und Kommunikationszentrum der RWTH Aachen
Seffenter Weg 23, D 52074 Aachen (Germany)
Phone: +49 241 80 24367 – Fax/UMS: +49 241 80 624367
> -----Original Message-----
> From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]]
> On Behalf Of Dominik Goeddeke
> Sent: Tuesday, March 12, 2013 10:32 PM
> To: Open MPI Users
> Subject: [OMPI users] bug in mpif90? OMPI_FC envvar does not work with
> 'use mpi'
> 
> Dear OMPI folks,
> 
> according to this FAQ entry
> 
> http://www.open-mpi.org/faq/?category=mpi-apps#override-wrappers-
> after-v1.0
> 
> one way to use the mpif90 compiler wrapper with another compiler than
> Open-MPI was built with is to set the envvar OMPI_FC to the other
compiler.
> 
> Using this simple toy code
> 
> > program test
> >   implicit none
> >   include 'mpif.h'
> >   integer :: ierr
> >   call MPI_Init(ierr)
> >   print *, "Hello"
> >   call MPI_Finalize(ierr)
> > end program test
> 
> I indeed see the expected (and documented) behaviour:
> 
> > bash$ export OMPI_FC=ifort
> > bash$ mpif90 test.f90
> > bash$ mpirun -np 3 ./a.out
> 
> Now, If I replace these two lines in the reproducer
> 
> > implicit none
> > include 'mpif.h'
> 
> with these two lines (which is actually the MPI-2 way of doing things, as
Jeff
> himself praises in this blog entry:
> http://blogs.cisco.com/performance/a-bucket-full-of-new-mpi-fortran-
> features)
> 
> > use mpi
> > implicit none
> 
> I get this as the output of mpif90:
> 
> > test.f90(7): error #7013: This module file was not generated by any
> > release of this compiler.   [MPI]
> > use mpi
> > ----^
> > compilation aborted for test.f90 (code 1)
> 
> There seems to be no language on this particular problem in the FAQs, so I
> assume this is either a documentation bug or an actual bug in the compiler
> wrappers. The approach is clearly marked as "not recommended", but
> actually, this problem can be quite a showstopper because on laptops,
> people (like me) are often too lazy to compile Open-MPI (and consequently,
> valgrind and friends) multiple times, especially since the FAQ says that
this
> should work :)
> 
> I am using the system gcc of ubuntu 12.04 (4.6.3-1ubuntu5) and OMPI 1.6.3.
> Of course everything works if I use a properly installed machine that
provides
> OpenMPI-builds for different compilers via modules, and also the oldish
> "include 'mpif.h'" approach is a sufficient workaround.
> 
> Thanks for any clarification, hope this reproducer helps,
> 
> Cheers,
> 
> Dominik
> 
> --
> Jun.-Prof. Dr. Dominik Göddeke
> Hardware-orientierte Numerik für große Systeme Institut für Angewandte
> Mathematik (LS III) Fakultät für Mathematik, Technische Universität
> Dortmund http://www.mathematik.tu-dortmund.de/~goeddeke
> Tel. +49-(0)231-755-7218  Fax +49-(0)231-755-5933
> 
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