[petsc-users] parallel computing error

[­권승리 / 학생 / 항공우주공학과]

Dear developers

Thank you for your explanation.

But I should use the MatCreateSeqDense because I want to use the
MatMatSolve that B matrix must be a SeqDense matrix.

Using MatMatSolve is an inevitable part of my code.

Could you give me a comment to avoid this error?

Best,

Seung Lee Kwon

2023년 5월 3일 (수) 오후 7:30, Matthew Knepley <knepley at gmail.com>님이 작성:

> On Wed, May 3, 2023 at 6:05 AM ­권승리 / 학생 / 항공우주공학과 <ksl7912 at snu.ac.kr>
> wrote:
>
>> Dear developers
>>
>> I'm trying to use parallel computing and I ran the command 'mpirun -np 4
>> ./app'
>>
>> In this case, there are two problems.
>>
>> *First,* I encountered error message
>> ///
>> [0]PETSC ERROR: [1]PETSC ERROR: --------------------- Error Message
>> --------------------------------------------------------------
>> [1]PETSC ERROR: Invalid argument
>> [1]PETSC ERROR: Comm must be of size 1
>> ///
>> The code on the error position is
>> MatCreateSeqDense(PETSC_COMM_SELF, nns, ns, NULL, &Kns));
>>
>
> 1) "Seq" means sequential, that is "not parallel".
>
> 2) This line should still be fine since PETSC_COMM_SELF is a serial
> communicator
>
> 3) You should be checking the error code for each call, maybe using the
> CHKERRQ() macro
>
> 4) Please always send the entire error message, not a snippet
>
>   THanks
>
>      Matt
>
>
>> Could "MatCreateSeqDense" not be used in parallel computing?
>>
>> *Second*, the same error message is repeated as many times as the number
>> of cores.
>> if I use command -np 4, then the error message is repeated 4 times.
>> Could you recommend some advice related to this?
>>
>> Best,
>> Seung Lee Kwon
>>
>> --
>> Seung Lee Kwon, Ph.D.Candidate
>> Aerospace Structures and Materials Laboratory
>> Department of Mechanical and Aerospace Engineering
>> Seoul National University
>> Building 300 Rm 503, Gwanak-ro 1, Gwanak-gu, Seoul, South Korea, 08826
>> E-mail : ksl7912 at snu.ac.kr
>> Office : +82-2-880-7389
>> C. P : +82-10-4695-1062
>>
>
>
> --
> 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/>
>


-- 
Seung Lee Kwon, Ph.D.Candidate
Aerospace Structures and Materials Laboratory
Department of Mechanical and Aerospace Engineering
Seoul National University
Building 300 Rm 503, Gwanak-ro 1, Gwanak-gu, Seoul, South Korea, 08826
E-mail : ksl7912 at snu.ac.kr
Office : +82-2-880-7389
C. P : +82-10-4695-1062
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