[petsc-users] Questions about PCEXOTIC

[Barry Smith]

  Thanks for your interest in this type of algorithm.

  As Pierre notes, the code is implemented only as a simple tutorial on one particular "exotic" wire basket-type algorithm. We don't recommend this implementation for more general algorithms or geometries. 

  The face dof represents some sort of "average" of the face solution, it is not a point value.

  Barry


> On May 21, 2025, at 4:51 AM, Pierre Jolivet <pierre at joliv.et> wrote:
> 
> 
> 
>> On 21 May 2025, at 10:41 AM, Edoardo Centofanti <edoardo.centofanti01 at universitadipavia.it> wrote:
>> 
>> 
>> Dear all,
>> 
>> I have some questions about the PCEXOTIC preconditioner:
>> 
>> 1- While the type "wirebasket" seems clear to me, I do not understand what is meant as "one dof per face" in the documentation referring to "face" type. Is it intended as the interpolation on the centre of the face or some mean value?
>> 
>> 2- Is it possible to change the overlap between the subdomains?
>> 
>> 3- Are there any plans of extending the implementation to unstructured grids (DMPlex-like)? The current one seems to rely heavily on DMDA
>> 
>> 4- Running some preliminary tests on GPU with a code of mine that works on CPU, I got the following error:
>> 
>>  ** On entry to cusparseSpMM_bufferSize(): dimension mismatch, matA.num_rows (15405) != matC.num_rows (44955) with opA = CUSPARSE_OPERATION_NON_TRANSPOSE
>> 
>> Is the preconditioner intended to run also on GPU or the error above comes from the fact that this feature has yet to be tested/fully implemented?
>> 
> 
> This preconditioner is very old and the code is barely maintained.
> There is a newer implementation of the GDSW preconditioner in PCMG, see https://urldefense.us/v3/__https://petsc.org/release/manualpages/PC/PCMGSetAdaptCoarseSpaceType/__;!!G_uCfscf7eWS!ZumKWSWq6NO-AQvGkbYva1mSwRd9bF0GiINdu1CHcu0VVODx8UduTv-c85YTwWQ9OAUxqtHsbIcrIBgM5xKHUvE$  <https://urldefense.us/v3/__https://petsc.org/release/manualpages/PC/PCMGSetAdaptCoarseSpaceType/__;!!G_uCfscf7eWS!ZDnv3udGFNlZEC_MRfLAqwvcvCObnaAjMCeyaW__UaecBvN3MkXrzOPwJJUSHXo80-xOQdLNnSf_nLmUd7bZxg$>
> 
> Thanks,
> Pierre
> 
>> Thank you in advance,
>> Best,
>> Edoardo
>> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20250521/f0bdefdf/attachment-0001.html>