On Wed, Nov 15, 2017 at 10:57 PM, Mark Lohry <mlo...@gmail.com> wrote:
> What are the limitations of ILU in parallel you're referring to? Does > Schwarz+local ILU typically fare better? > Anecdotally, the sweet spot for ILU(k) k > 0 is extremely small. For smaller problems, sparse direct is so good its hard to win with ILU(k) since you do at least a few iterates. For larger problems, ILU(k) runs out of gas or memory fairly fast, and its better to find a method tailored to the problem. Matt > On Nov 15, 2017 10:50 PM, "Smith, Barry F." <bsm...@mcs.anl.gov> wrote: > >> >> >> > On Nov 15, 2017, at 9:40 PM, Jed Brown <j...@jedbrown.org> wrote: >> > >> > "Smith, Barry F." <bsm...@mcs.anl.gov> writes: >> > >> >>> On Nov 15, 2017, at 6:38 AM, Mark Lohry <mlo...@gmail.com> wrote: >> >>> >> >>> I've found ILU(0) or (1) to be working well for my problem, but the >> petsc implementation is serial only. Running with -pc_type hypre >> -pc_hypre_type pilut with default settings has considerably worse >> convergence. I've tried using -pc_hypre_pilut_factorrowsize (number of >> actual elements in row) to trick it into doing ILU(0), to no effect. >> >>> >> >>> Is there any way to recover classical ILU(k) from pilut? >> >>> >> >>> Hypre's docs state pilut is no longer supported, and Euclid should be >> used for anything moving forward. pc_hypre_boomeramg has options for Euclid >> smoothers. Any hope of a pc_hypre_type euclid? >> >> >> >> Not unless someone outside the PETSc team decides to put it back in. >> > >> > PETSc used to have a Euclid interface. My recollection is that Barry >> > removed it because users were finding too many bugs in Euclid and >> > upstream wasn't fixing them. A contributed revival of the interface >> > won't fix the upstream problem. >> >> The hypre team now claims they care about Euclid. But given the >> limitations of ILU in parallel I can't imagine anyone cares all that much. >> >> >> -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
