[petsc-dev] PCASM uses DMCreateDecomposition which splits field, NOT expected behavior

[Jed Brown]

On Sat, May 26, 2012 at 10:24 PM, Dmitry Karpeev <karpeev at mcs.anl.gov>wrote:

> How about having a DM-specific function for that designation?
>>
> DMXXXGetFieldSplits()/DMXXXGetDomainDecompositions(), for example?
>

For the C interface, maybe configure a named set with DMXxxSet... and tell
PCASM to use it. For the options database interface, maybe have the option
processed by DMXxx code instead of by PCASM. I don't know, this might be
just as bad.


> I think that would work, if the implementation defined only a small number
> of decompositions.
> If instead there is a short grammar defining well-formed strings naming
> such decompositions, I'm not sure how to
> communicate that to the user, other than in documentation.  I have
> DMLibMeshGetVars() to return all vars.  FieldSplits
> can be defined as arbitrary groupings of those.  Each split will then
> advertise only the vars in the groupings that defines the split.
>

I still don't know what to do about a nonlinear change of basis.
Advertising var names seems reasonable to me.

Note that ASM domains are essentially vertex-oriented which is different
from element-centered domains (natural for non-overlapping methods).
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