[petsc-users] DMPlexCreateSection crashed with larger number of processors

[Matthew Knepley]

On Sat, Jul 9, 2022 at 8:34 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Fri, Jul 8, 2022 at 7:41 PM Mike Michell <mi.mike1021 at gmail.com> wrote:
>
>> As a follow-up, just "depth" default label was provided to avoid NULL
>> PETScIS, and it seems working.
>>
>
> Ah, "depth" is definitely required and is produced by DMPlexStratify(). I
> will put in a check for this so that you get a good error message.
>

I cannot find an instance of an IS being pulled from the depth label here.
Do you have something I can run that shows this fault?

  Thanks,

     Matt


>   Thanks!
>
>      Matt
>
>
>> Thanks,
>> Mike
>>
>>
>>> It looks like NULL PETScIS is obtained from DMGetStratumIS() which is
>>> shown in the previously attached code. Currently, "marker" label is used to
>>> define default bcPointIS pointer with numBC=1 through DMGetStratumIS(), and
>>> it seems that if a certain proc does not have any boundary from this
>>> "marker" label, the DMPlexCreateSection() crashes.
>>>
>>> The PETSc's manual page for DMPlexCreateSection() says "bcPoints" is an
>>> IS holding points to which each boundary condition applies. So, by
>>> including no boundary for a certain distributed mesh block, it looks very
>>> natural that this function crashes. How can I not to pass a NULL PETScIS in
>>> this case? Is there any specific way for that (or a trick)?
>>>
>>> Thanks,
>>> Mike
>>>
>>>
>>>> On Wed, Jul 6, 2022 at 3:42 PM Mike Michell <mi.mike1021 at gmail.com>
>>>> wrote:
>>>>
>>>>> I am passing NULL for IS Permutation as;
>>>>>
>>>>> call
>>>>> DMPlexCreateSection(dm_geom,nolabel,pNumComp,pNumDof,numBC,pBcField,pBcCompIS,pBcPointIS,PETSC_NULL_IS,section,ierr)
>>>>>
>>>>> Should I define non-NULL IS Permutation before I call
>>>>> DMPlexCreateSection() to avoid the issue?
>>>>>
>>>>
>>>> No, the problem is not the perm argument. To be sure, we should get a
>>>> stack trace with line numbers (use a debug build). To me it looked
>>>> like you passed a NULL IS to DMAddBoundary().
>>>>
>>>>   Thanks,
>>>>
>>>>     Matt
>>>>
>>>>
>>>>> Thanks,
>>>>> Mike
>>>>>
>>>>>
>>>>> On Wed, Jul 6, 2022 at 12:57 PM Mike Michell <mi.mike1021 at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Hi, I am using DMPlex for a FVM code written in Fortran that uses
>>>>>>> DMPlexCreateSection() to prepare an output file in vtu format. A domain of
>>>>>>> interest has around 5000 node points and with small number of processors
>>>>>>> (such as nproc=3), the DMPlexCreateSection() works fine. However, if a
>>>>>>> larger number of procs (such as nproc=20) is used,  DMPlexCreateSection()
>>>>>>> crashes with error message below. It looks very similar problem in a
>>>>>>> previous PETSc user inquiry: " [petsc-dev] DMPlexCreateSection
>>>>>>> crash in a no-boundary corner case
>>>>>>> <https://lists.mcs.anl.gov/pipermail/petsc-dev/2013-November/014049.html>
>>>>>>> "
>>>>>>>
>>>>>>
>>>>>> Yes, the recommendation is not to pass a NULL PetscIS to the
>>>>>> AddBoundary() routine. Are you doing this?
>>>>>>
>>>>>>   Thanks,
>>>>>>
>>>>>>      Matt
>>>>>>
>>>>>>
>>>>>>
>>>>>>> When I call DMPlexCreateSection(), a nullified pointer
>>>>>>> "nolabel(:)=>NULL()" is provided. What is a possible solution to this
>>>>>>> problem? It looks like there is a problem with a processor that does not
>>>>>>> have any boundaries. A piece of the source code is attached to show how
>>>>>>> the  DMPlexCreateSection() is used in the code.
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Mike
>>>>>>>
>>>>>>> [16]PETSC ERROR: --------------------- Error Message
>>>>>>> --------------------------------------------------------------
>>>>>>> [16]PETSC ERROR: Null argument, when expecting valid pointer
>>>>>>> [16]PETSC ERROR: Null Pointer: Parameter # 1
>>>>>>> [16]PETSC ERROR: See https://petsc.org/release/faq/ for trouble
>>>>>>> shooting.
>>>>>>> [16]PETSC ERROR: Petsc Release Version 3.17.0, unknown
>>>>>>> [16]PETSC ERROR: #1 ISGetLocalSize() at
>>>>>>> [16]PETSC ERROR: #2 DMPlexCreateSectionBCDof() at
>>>>>>> [16]PETSC ERROR: #3 DMPlexCreateSection() at
>>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> 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/>
>>>>>>
>>>>>
>>>>
>>>> --
>>>> 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/>
>>>>
>>>
>
> --
> 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/>
>


-- 
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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