[petsc-users] Scraping MPI information from PETSc conf

[Alexander Lindsay]

Is it safe to assume that mpicxx will always add the requisite include and library flags? Are there any/many implementations that do not take the -show flag?

> 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
>> 
>