[petsc-users] --with-mpi=0

[Barry Smith]

  It seems like this might be a good strategy, presumably the directory is already made to hold mpi.h for MPI uni

 Perhaps its possible to change our installer to have mpiuni's mod file at  prefix/include/petsc/mpiuni/mpi.mod - [to enable reusing mpi.mod name ]

> On Dec 18, 2021, at 4:36 PM, Satish Balay <balay at mcs.anl.gov> wrote:
> 
> Sure - that's the trade-off.
> 
> At some point I think we decided not to map mpiuni.mod to mpi.mod [to avoid potential clash with other mpi/mpiuni type impls].
> 
> If I remember correctly - we could limit on the C side - by not installing mpi.h in std location [its at include/petsc/mpiuni/mpi.h]
> 
> And since mpiuni's mpi.mod is to be installed in prefix/include - I think this different name was chosen.
> 
> And now that we are supporting 'use mpi or mpi_f08' - its 'use mpiuni or mpi or mpi_f08' or use --with-mpi-f90module-visibility=1
> 
> For now petscmpi maps to mpi or mpiuni.
> 
> Perhaps its possible to change our installer to have mpiuni's mod file at  prefix/include/petsc/mpiuni/mpi.mod - [to enable reusing mpi.mod name ]
> 
> [at some point we had an option to skip fortran mpi_comm_rank() etc - as they would clash with similar uni impls. But I see that option no longer exists?]
> 
> Satish
> 
> On Sat, 18 Dec 2021, Barry Smith wrote:
> 
>> 
>>  Urg, this is pretty horrible. petscmpi?  Why can't MPIUNI provide this as "standard" MPI modules?
>> 
>> 
>> 
>>> On Dec 18, 2021, at 11:04 AM, Satish Balay via petsc-users <petsc-users at mcs.anl.gov> wrote:
>>> 
>>> Ah - you need 'use petscmpi'
>>> 
>>> For example: ksp/ksp/tutorials/ex44f.F90
>>> 
>>> Satish
>>> 
>>> On Sat, 18 Dec 2021, Matthew Knepley wrote:
>>> 
>>>> On Sat, Dec 18, 2021 at 9:26 AM Tabrez Ali <tabrezali at gmail.com> wrote:
>>>> 
>>>>> Hi,
>>>>> 
>>>>> I am trying to compile Fortran code with PETSc 3.16 built without MPI,
>>>>> i.e., --with-mpi=0, and am getting the following error:
>>>>> 
>>>>>  call MPI_Comm_rank(MPI_COMM_WORLD,rank,ierr)
>>>>>                                        1
>>>>> Error: Symbol ‘mpi_comm_world’ at (1) has no IMPLICIT type
>>>>> 
>>>> 
>>>> Hi Tabrez,
>>>> 
>>>> The definition of MPI_COMM_WORLD is in mpif.h. Are you #including that?
>>>> 
>>>> Thanks,
>>>> 
>>>>   Matt
>>>> 
>>>> 
>>>>> There are no issues with PETSc 3.14 or prior versions. Any ideas as to
>>>>> what could be wrong?
>>>>> 
>>>>> I do see the following note (below) in
>>>>> https://petsc.org/main/docs/changes/315/ but I am not sure if it's
>>>>> related:
>>>>> 
>>>>> *Add configure option --with-mpi-f90module-visibility [default=``1``].
>>>>> With 0, mpi.mod will not be visible in use code (via petscsys.mod) -
>>>>> so mpi_f08 can now be used*
>>>>> 
>>>>> Regards,
>>>>> 
>>>>> Tabrez
>>>>> 
>>>> 
>>>> 
>>>> 

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