[petsc-users] Questions about PCEXOTIC

[Edoardo Centofanti]

Dear all,

Thank you for your answers.
Do you know which options are required for a typical use case of GDSW in
PCMG? However, I imagine that only structured DMDA meshes can be employed
with it.

Best,
Edoardo

Il giorno mer 21 mag 2025 alle ore 16:52 Barry Smith <bsmith at petsc.dev> ha
scritto:

>
>   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!Zmi6sdgeoCOMy1lkVGYn-ac5wvH3QEcOkYQ2VzdQgCqLY8nIVkX1oi_yt5S2vJDcF5BT8mmzOLmOUEK483D0v9_aZe01iy1b20hMB1HPuOE$ 
> <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
>
>
>

-- 
Edoardo Centofanti
Dipartimento di Matematica 'Felice Casorati'
Università degli Studi di Pavia

Tel. 0382985608  |  Ufficio A14  |  Via Ferrata 5, 27100 Pavia, Italy
<https://urldefense.us/v3/__https://maps.google.com/?q=Via*20Ferrata*205,*2027100*20Pavia,*20Italy__;JSUlJSU!!G_uCfscf7eWS!Zmi6sdgeoCOMy1lkVGYn-ac5wvH3QEcOkYQ2VzdQgCqLY8nIVkX1oi_yt5S2vJDcF5BT8mmzOLmOUEK483D0v9_aZe01iy1b20hMoN_kNHg$ >
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