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

[Smith, Barry F.]

> On Mar 16, 2018, at 11:54 AM, 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?
>> 
>> 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?

   From the installation instructions: http://www.mcs.anl.gov/petsc/documentation/installation.html

If you are behind a firewall and cannot use a proxy for the downloads or have a very slow network use the additional option --with-packages-dir=/adirectory. This will trigger ./configure to print the URLs of all the packages you must download this directory (do not uncompress or untar the files) and then use these copies of the packages instead of trying to download them directly from the internet.



>>   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/channel/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/
>