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Subject: Re: [OMPI users] fortran program with integer kind=8 using openmpi
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-06-29 07:03:18


On Jun 28, 2012, at 8:37 PM, David Warren wrote:

> You should not have to recompile openmpi, but you do have to use the correct type. You can check the size of integers in your fortrana nd use MPI_INTEGER4 or MPI_INTEGER8 depending on what you get.

If you configure ompi with -fdefault-integer-8, then OMPI will assume that Fortran integers are always 8 bytes, so be sure to also compile all of your MPI applications the same way. Indeed, you may want to configure OMPI with something like:

./configure FCFLAGS=-fdefault-integer-8 FFLAGS=-fdefault-integer-8 \
   --with-wrapper-fflags=-fdefault-integer-8 \
   --with-wrapper-fcflags=-fdefault-integer-8

This will add -fdefault-integer-8 to the mpif77 and mpif90 command lines automatically so that you *can't* compile without that flag.

Be aware that 8-byte Fortran integers *should work* in Open MPI, but it is probably not well tested. You may well run into some issues; be sure to let us know if you run into bugs. Sending small test programs that show the problem are usually the best way to help us identify/fix the precise problem.

> in gfortran use
> integer i
> if(sizeof(i) .eq. 8) then
> mpi_int_type=MPI_INTEGER8
> else
> mpi_int_type=MPI_INTEGER4
> endif

I don't think that this should be necessary -- as long as you configured OMPI with the 8-byte-integer setting, then MPI_INTEGER should represent an 8 byte integer.

-- 
Jeff Squyres
jsquyres_at_[hidden]
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