[petsc-users] Problem with solving Poisson eqn for some cases

[Matthew Knepley]

On Fri, Mar 16, 2018 at 12:54 PM, TAY wee-beng <zonexo at gmail.com> wrote:

>
> On 15/3/2018 6:21 PM, Matthew Knepley wrote:
>
> On Thu, Mar 15, 2018 at 3:51 PM, TAY wee-beng <zonexo at gmail.com> wrote:
>
>> Hi,
>>
>> I'm running a CFD code which solves the momentum and Poisson eqns.
>>
>> Due to poor scaling with HYPRE at higher cpu no., I decided to try using
>> PETSc with boomeramg and gamg.
>>
>> I tested for some small cases and it work well. However, for the large
>> problem which has poor scaling, it gives an error when I change my Poisson
>> solver from pure HYPRE to PETSc with boomeramg and gamg.
>>
>> The error is :
>>
>> Caught signal number 11 SEGV: Segmentation Violation, probably memory
>> access out of range
>>
>> I tried using:
>>
>> -poisson_ksp_type richardson -poisson_pc_type hypre
>> -poisson_pc_type_hypre boomeramg
>>
>> -poisson_ksp_type gmres -poisson_pc_type hypre -poisson_pc_type_hypre
>> boomeramg
>>
>> -poisson_pc_type gamg -poisson_pc_gamg_agg_nsmooths 1
>>
>> but they all gave similar error.
>>
>> So why is this so? How should I troubleshoot? I am now running a debug
>> ver of PETSc to check the error msg.
>
>
> 1) For anything like this, we would like to see a stack trace from the
> debugger or valgrind output.
>
> 2) We do have several Poisson examples. Does it fail for you on those?
>
> Hi,
>
> Can you recommend me some suitable egs? Esp in Fortran?
>

Here is 2D Poisson


https://bitbucket.org/petsc/petsc/src/4b6141395f14f0c7d1415a2ff0158eec75a27d63/src/snes/examples/tutorials/ex5f.F90?at=master&fileviewer=file-view-default


>
> 3) You can also try ML, which is the same type of MG as GAMG.
> (--download-ml).
>
> My cluster can't connect to the internet. Where can I 1st download it?
>
> Similarly, how can I find out the location of the ext software by myself?
>

The locations are all in the configure Python modules:


https://bitbucket.org/petsc/petsc/src/4b6141395f14f0c7d1415a2ff0158eec75a27d63/config/BuildSystem/config/packages/ml.py?at=master&fileviewer=file-view-default

  Thanks,

    Matt


>   Thanks,
>
>      Matt
>
>
>>
>> --
>> Thank you very much.
>>
>> Yours sincerely,
>>
>> ================================================
>> TAY Wee-Beng (Zheng Weiming) 郑伟明
>> Personal research webpage: http://tayweebeng.wixsite.com/website
>> Youtube research showcase: https://www.youtube.com/channe
>> l/UC72ZHtvQNMpNs2uRTSToiLA
>> linkedin: www.linkedin.com/in/tay-weebeng
>> ================================================
>>
>>
>
>
> --
> 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.caam.rice.edu/%7Emk51/>
>
>
>


-- 
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.caam.rice.edu/~mk51/>
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