[petsc-users] MatView to file

[Mark Adams]

So your build/machine works with ex54.
That is a nine-point stencil so about 2x larger than your problem, but your
problem fails.
Is that correct?

On Fri, Aug 12, 2022 at 3:47 PM Alfredo Jaramillo <ajaramillopalma at gmail.com>
wrote:

> Hello Mark,
> But why should this depend on the number of processes?
> thanks
> Alfredo
>
> On Fri, Aug 12, 2022 at 1:42 PM Mark Adams <mfadams at lbl.gov> wrote:
>
>> With 4 million elements you are nowhere near the 32 but integer limit of
>> 2B or 32Gb of memory.
>>
>> See the https://petsc.org/main/docs/manualpages/Mat/MatView
>> You should go to binary format when doing large matrices.
>>
>> Mark
>>
>> On Fri, Aug 12, 2022 at 1:00 PM Alfredo Jaramillo <
>> ajaramillopalma at gmail.com> wrote:
>>
>>> Hello Mark,
>>> Thank you, I added the lines that you sent.
>>> This only happens when running the code with more than 1 process. With
>>> only 1 MPI process the matrix is printed out.
>>> With 2 processes or more I observed the program begins to allocate RAM
>>> until it exceeds the computer capacity (32GB) so I wasn't able to get the
>>> stack trace.
>>>
>>> However, I was able to reproduce the problem by compiling
>>> src/ksp/ksp/tutorials/ex54.c.html
>>> <https://petsc.org/release/src/ksp/ksp/tutorials/ex54.c.html>
>>> (modifying line 144) and running it with
>>>
>>> mpirun -np 2 ex54 -ne 1000
>>>
>>> This gives a sparse matrix of order ~1 million. When running ex54 with
>>> only one MPI process I don't observe this excessive allocation and the
>>> matrix is printed out.
>>>
>>> Thanks,
>>> Alfredo
>>>
>>>
>>>
>>> On Fri, Aug 12, 2022 at 10:02 AM Mark Adams <mfadams at lbl.gov> wrote:
>>>
>>>> You also want:
>>>>
>>>>     PetscCall(PetscViewerPopFormat(viewer));
>>>>     PetscCall(PetscViewerDestroy(&viewer));
>>>>
>>>> This should not be a problem.
>>>> If this is a segv and you configure it with   '--with-debugging=1', you
>>>> should get a stack trace, which would help immensely.
>>>> Or run in a debugger to get a stack trace.
>>>>
>>>> Thanks,
>>>> Mark
>>>>
>>>>
>>>>
>>>> On Fri, Aug 12, 2022 at 11:26 AM Alfredo Jaramillo <
>>>> ajaramillopalma at gmail.com> wrote:
>>>>
>>>>> Dear developers,
>>>>>
>>>>> I'm writing a sparse matrix into a file by doing
>>>>>
>>>>>     if (dump_mat) {
>>>>>         PetscViewer viewer;
>>>>>         PetscViewerASCIIOpen(PETSC_COMM_WORLD,"mat-par-aux.m",&viewer);
>>>>>         PetscViewerPushFormat(viewer, PETSC_VIEWER_ASCII_MATLAB);
>>>>>         MatView(A,viewer);
>>>>>     }
>>>>>
>>>>> This works perfectly for small cases.
>>>>> The program crashes for a case where the matrix A is of order 1
>>>>> million but with only 4 million non-zero elements.
>>>>>
>>>>> Maybe at some point petsc is full-sizing A?
>>>>>
>>>>> Thank you,
>>>>> Alfredo
>>>>>
>>>>
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