[petsc-dev] BlockGetIndices and GetBlockIndices

[Lawrence Mitchell]

On Wed, 16 Oct 2019 at 15:54, Jed Brown via petsc-dev <petsc-dev at mcs.anl.gov>
wrote:

> Stefano Zampini <stefano.zampini at gmail.com> writes:
>
> > I just took a look at the ISGENERAL code. ISSetBlockSize_General just
> sets the block size of the layout (??)
> > ISGetIndices always return the data->idx memory.
> > So, a more profound question is: what is the model behind setting the
> block size on a ISGENERAL? And on a IS in general?
>
> My recollection is that it was added to support MatNest and
> MatGetLocalSubMatrix preserving block sizes so that MatSetValuesBlocked
> could be used.


We use it for this purpose (certainly ISStride, I think ISGeneral)

LAWRENCE
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