[petsc-users] Scraping MPI information from PETSc conf

[Jed Brown]

Alexander Lindsay <alexlindsay239 at gmail.com> writes:

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

It it's mpicxx, but such wrappers are not necessarily used.

The compile-time macro checks are more reliable than implementing a bunch of cases for MPI library layout and identification.

> 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
>>> 
>>