Jed Brown writes: > On Mon, Jan 2, 2012 at 21:58, Dave Nystrom <dnystrom1 at comcast.net> wrote: > > > I'm wondering if petsc has support for reordering the unknowns under the > > hood so that for the z-coupling case, the matrix can be cast as a compact > > tridiagonal matrix. Essentially, this would be support for minimizing the > > bandwidth. > > -pc_factor_mat_ordering_type rcm > > You can get this with MatGetOrdering(A,MATORDERINGRCM,&isrow,&iscol) > > We need to write man pages for all the MatOrderingTypes (RCM, ND, etc)
Thanks. I just tried a run with -ksp_type cg -pc_type cholesky -pc_factor_mat_ordering_type rcm -log_summary and did not see a performance difference. I'm trying to reproduce the results of our home grown cg with cholesky preconditioner but for some reason, I am getting about 3x the iteration count as I get with our home grown cg with cholesky preconditioner using the z-coupling. Not sure what is wrong. Maybe I have a bug. Is there any kind of increased level of verbosity that tell me things like initial bandwidth of the matrix and the bandwidth after reordering? Thanks, Dave
