[petsc-users] petsc compiled without MPI

[Matthew Knepley]

On Mon, Feb 27, 2023 at 8:41 AM Long, Jianbo <jl7037 at mun.ca> wrote:

> Thanks for the explanations ! It turns out the issue of running
> sequentially compiled petsc is PetscFinalize() function. Since my
> subroutine involving petsc functions needs to be called multiple times in
> the program, I have to comment out PetscFinalize() at the end of the
> subroutine, otherwise at the next call of this subroutine, petsc would stop
> and throw out an error about MPI_Comm_set_errhandler !
>

Yes, you are supposed to call PetscInitialize() _once_ at the beginning of
the program, and PetscFinalize() _once_ at the end of the program.

  Thanks,

    Matt


> Jianbo
>
> On Sun, Feb 26, 2023 at 4:39 PM Satish Balay <balay at mcs.anl.gov> wrote:
>
>> On Sun, 26 Feb 2023, Pierre Jolivet wrote:
>>
>> >
>> >
>> > > On 25 Feb 2023, at 11:44 PM, Long, Jianbo <jl7037 at mun.ca> wrote:
>> > >
>> > > Hello,
>> > >
>> > > For some of my applications, I need to use petsc without mpi, or use
>> it sequentially. I wonder where I can find examples/tutorials for this ?
>> >
>> > You can run sequentially with just a single MPI process (-n 1).
>>
>> even if you build with mpich/openmpi - you can run sequentially without
>> mpiexec - i.e:
>>
>> ./binary
>>
>> One reason to do this [instead of building PETSc with --with-mpi=0] - is
>> if you are mixing in multiple pkgs that have MPI dependencies [in which
>> case - its best to build all these pkgs with the same mpich or openmpi -
>> but still run sequentially].
>>
>> Satish
>>
>> > If you need to run without MPI whatsoever, you’ll need to have a
>> separate PETSc installation which was configured --with-mpi=0
>> > In both cases, the same user-code will run, i.e., all PETSc examples
>> available with the sources will work (though some are designed purely for
>> parallel experiments and may error out early on purpose).
>> >
>> > Thanks,
>> > Pierre
>> >
>> > > Thanks very much,
>> > > Jianbo Long
>> >
>> >
>>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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