[petsc-users] Allocating memory for off-diagonal matrix blocks when using DMComposite

[Jed Brown]

Gautam Bisht <gbisht at lbl.gov> writes:

> Hi,
>
> The comment on line 419 of SNES ex 28.c
> <http://www.mcs.anl.gov/petsc/petsc-current/src/snes/examples/tutorials/ex28.c.html>
> says
> that the approach used in this example is not the best way to allocate
> off-diagonal blocks. Is there an example that shows a better way off
> allocating memory for off-diagonal matrix blocks when using DMComposite?

The problem is that the allocation interfaces specialize on the matrix
type.  Barry wrote a DMCompositeSetCoupling(), but there are no
examples.  This is something that PETSc needs to improve.  I have been
unsuccessful at conceiving a _simple_ yet flexible/extensible solution.
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