[petsc-users] Scraping MPI information from PETSc conf

[Satish Balay]

On Sun, 1 Mar 2020, Alexander Lindsay wrote:

> Is it safe to assume that mpicxx will always add the requisite include and library flags?

Yes. There are always broken compilers. Similarly - there can always be broken mpi compilers aswell.

> Are there any/many implementations that do not take the -show flag?

For ex: cray. [they don't have 'mpicc', and no 'mpicc -show' or 'cc -show' ]

Satish

> 
> > On Feb 27, 2020, at 7:15 PM, Satish Balay <balay at mcs.anl.gov> wrote:
> > 
> > Not really useful for autotools - but we print the mpi.h used during
> > build in make.log
> > 
> > Using mpi.h: # 1 "/home/petsc/soft/mpich-3.3b1/include/mpi.h" 1
> > 
> > I guess the same code [using a petsc makefile] - can be scripted and
> > parsed to get the PATH to compare in autotools.
> > 
> > However the current version check [below] is likely the best way. Our
> > prior check was deemed too strict - for ex: when linux distros updated
> > MPI packages with a bug fixed version [without API change] - our prior
> > check flagged this as incompatible - so we had to change it.
> > 
> > Satish
> > 
> >> On Thu, 27 Feb 2020, Jed Brown wrote:
> >> 
> >> If determining mpicc is sufficient, this will work
> >> 
> >>  pkg-config --var=ccompiler PETSc
> >> 
> >> We also define
> >> 
> >> $ grep NUMVERSION mpich-optg/include/petscconf.h 
> >> #define PETSC_HAVE_MPICH_NUMVERSION 30302300
> >> 
> >> or
> >> 
> >> $ grep OMPI_ ompi-optg/include/petscconf.h 
> >> #define PETSC_HAVE_OMPI_MAJOR_VERSION 4
> >> #define PETSC_HAVE_OMPI_MINOR_VERSION 0
> >> #define PETSC_HAVE_OMPI_RELEASE_VERSION 2
> >> 
> >> which PETSc uses to raise a compile-time error if it believes you're
> >> compiling PETSc code using an incompatible MPI.
> >> 
> >> Note that some of this is hidden in the environment on Cray systems, for
> >> example, where CC=cc regardless of what compiler you're actually using.
> >> 
> >> Alexander Lindsay <alexlindsay239 at gmail.com> writes:
> >> 
> >>> What's the cleanest way to determine the MPI install used to build PETSc?
> >>> We are configuring a an MPI-based C++ library with autotools  that will
> >>> eventually be used by libMesh, and we'd like to make sure that this library
> >>> (as well as libMesh) uses the same MPI that PETSc used or at worst detect
> >>> our own and then error/warn the user if its an MPI that differs from the
> >>> one used to build PETc. It seems like the only path info that shows up is
> >>> in MPICXX_SHOW, PETSC_EXTERNAL_LIB_BASIC, and PETSC_WITH_EXTERNAL_LIB (I'm
> >>> looking in petscvariables). I'm willing to learn the m4/portable shell
> >>> built-ins necessary to parse those variables and come out with an mpi-dir,
> >>> but before doing that figured I'd ask here and see if I'm missing something
> >>> easier.
> >>> 
> >>> Alex
> >> 
> > 
>