[petsc-users] Scraping MPI information from PETSc conf

[Satish Balay]

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
>