bsmith at mcs.anl.gov
Mon Aug 24 14:38:05 CDT 2009
The high-level DMMG interface to PETSc's linear multigrid
currently only generates AIJ or BAIJ matrices and hence the easy
support for -dmmg_grid_sequence
only works for AIJ or BAIJ matrices. Sorry about this.
A temporary fix for this would be to modify DAGetMatrix() to also
accept MATMFFD type and generate the right matrix in that case. If you
know C you can easily add
this; the code is in src/dm/da/utils/fdda.c
My long term plan is for DAGetMatrix() to actually take as input a
matrix whose type has been set and then just add additional
information to it. For matrix-free it would
just add the matrix sizes, for AIJ and BAIJ it would add the
preallocation and nonzero structure.
On Aug 19, 2009, at 10:54 PM, Hal Finkel wrote:
> I'd like to try using a matrix-free Newton method with a multigrid
> object configured with -dmmg_grid_sequence, but I don't understand
> how. Using SNES directly, I can set -snes_mf, but this does not
> seems to work with the multigrid object, and DMMGSetSNES() always
> allocates a matrix.
> Thank you in advance,
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