[petsc-users] Nonzero I-j locations

[Jed Brown]

"Smith, Barry F. via petsc-users" <petsc-users at mcs.anl.gov> writes:

>    This is an interesting idea, but unfortunately not directly compatible with libMesh filling up the finite element part of the matrix. Plus it appears MatGetLocalSubMatrix() is only implemented for IS and Nest matrices :-(

Maybe I'm missing something, but MatGetLocalSubMatrix *is* implemented
for arbitrary Mats; it returns a view that allows you to set entries
using local submatrix indexing.  That was a key feature of the MatNest
work from so many years ago and a paper on which you're coauthor.  ;-)