[petsc-users] error with version 3.17.1

[Mark Adams]

I'm glad that was easy to deal with.

We need to clarify this.

Thanks,
Mark

On Tue, May 3, 2022 at 5:55 PM Randall Mackie <rlmackie862 at gmail.com> wrote:

>
> On May 3, 2022, at 12:37 PM, Mark Adams <mfadams at lbl.gov> wrote:
>
>
>> Are you saying that now you have to explicitly set each 3x3 dense block,
>> even if they are not used and that was not the case before?
>>
>>
>> That was always the case before, you may have misinterpreted the meaning
>> of a Mat block size?
>>
>
> Actually block size is really more of a hint in that you don't have to set
> 3x3 dense blocks and thus any AIJ matrix can have any block size
> essentially.
> At least that is my understanding.
> There is a CI test that has sparse blocks and I ran into this issue with
> GAMG optimizations.
> (I had to add complicated code that Pierre actually found a bug in.)
>
> I don't know what changed in PETSc to make ASM fail for you, but if
> MatConvert and ASM fail then PETSc is broken and always has been.
>
> I did not follow this whole thread, but Randall could you change your code
> to add dense blocks or not use block size?
> Sorry, but I just don't think we should support this (Pierre seems to
> think that we do not) and we should "depreciate" this.
> This needs to be discussed of course.
>
> Mark
>
>
> Hi Mark and Pierre,
>
> You are correct that it is not necessary to use the block size. I had done
> that many many years ago because for some reason I thought it was necessary
> when creating a matrix for a 3D grid with more than 1 degree of freedom per
> node.
>
> But as long as the matrix entries are set correctly, block size doesn’t
> really matter.
>
> I think part of the issue in my situation is that there are parts of the
> matrix where not all 3x3 dense blocks are set due to representing a
> staggered grid system using a 3D DMDA (but like I say this was done many
> years before DMStag was developed).
>
>
> Thanks for the help and the clarifications,
>
> Randy
>
>
>
>
>
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