[petsc-users] Question about time issues in parallel computing

[Mark Adams]

Speed up to 4 processors should have at least 40,000 equations for 3D
problems and more for 2D.
At least for iterative solvers. This is probably a good place to start with
direct solvers but you might see benefit with a little less.

Mark

On Wed, Mar 15, 2023 at 9:09 PM ­권승리 / 학생 / 항공우주공학과 <ksl7912 at snu.ac.kr>
wrote:

> Thank you for your reply.
>
> It was a simple problem, but it has more than 1000 degrees of freedom.
>
> Is this not enough to check speedup?
>
> Best regards
> Seung Lee Kwon
>
> 2023년 3월 15일 (수) 오후 8:50, Matthew Knepley <knepley at gmail.com>님이 작성:
>
>> On Wed, Mar 15, 2023 at 3:38 AM ­권승리 / 학생 / 항공우주공학과 <ksl7912 at snu.ac.kr>
>> wrote:
>>
>>> Dear petsc developers.
>>>
>>> Hello.
>>> I am trying to solve the structural problem with FEM and test parallel
>>> computing works well.
>>>
>>> However, even if I change the number of cores, the total time is
>>> calculated the same.
>>>
>>> I have tested on a simple problem using a MUMPS solver using:
>>> mpiexec -n 1
>>> mpiexec -n 2
>>> mpiexec -n 4
>>> ...
>>>
>>> Could you give me some advice if you have experienced this problem?
>>>
>>
>> If your problem is small, you could very well see no speedup:
>>
>>
>> https://petsc.org/main/faq/#what-kind-of-parallel-computers-or-clusters-are-needed-to-use-petsc-or-why-do-i-get-little-speedup
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>> Best regards
>>> 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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