> On 30 Jul 2015, at 17:13, Garth N. Wells <gn...@cam.ac.uk> wrote: > > > On 30 July 2015 at 13:19, Mikael Mortensen <mikael.morten...@gmail.com > <mailto:mikael.morten...@gmail.com>> wrote: > >> On 30 Jul 2015, at 13:54, Jan Blechta <blec...@karlin.mff.cuni.cz >> <mailto:blec...@karlin.mff.cuni.cz>> wrote: >> >> On Thu, 30 Jul 2015 12:27:47 +0100 >> "Garth N. Wells" <gn...@cam.ac.uk <mailto:gn...@cam.ac.uk>> wrote: >> >>> On 30 July 2015 at 12:18, Mikael Mortensen >>> <mikael.morten...@gmail.com <mailto:mikael.morten...@gmail.com>> wrote: >>> >>>> Hi >>>> >>>> Back from vacation and very pleased :-) to find that I can update my >>>> Fenics installation to version 1.6 in less than 10 minutes! Used to >>>> take at least a few days. >>>> >>>> Now I’m trying to upgrade my applications to 1.6 and I just found >>>> that some of the common preconditioners (jacobi, bjacobi, >>>> additive_schwarz) have gone missing. Any reason for this or is it a >>>> mistake? They seem to have disappeared recently from the map >>>> _methods_descr in PETScPreconditioner.cpp. >>>> >>>> >>> The code in question was a mess and the wrapping approach >>> unsustainable, which is why it was removed. > > Including these three lines in creating _methods_descr in > PETScPreconditioner.cpp seems to work. Why do you consider it messy? > > {"jacobi", "Jacobi iteration"}, > {"bjacobi", "Block Jacobi iteration"}, > {"additive_schwarz", "Additive Schwarz"}, > > > Removing the first two was an error by me when stripping out CUSP. They can > go back. I'll blame my mistake on some bad indentation of an #ifedf ;). >
Yes, I see that one. > It's not sensible to provide Additive Schwarz since it has a raft of options > that should be set on it, but we can't sustainably wrap these. With the > forthcoming design clean up, a user will have complete control over an > Additive Schwarz PC. Ok, so do you suggest removing additive_schwarz then and keeping the other two, or keep also additive_schwarz until 1.7? In case schwarz is removed we need to do a bit of cleaning up, since schwarz has a parameter (in Krylovsolver::default_parameters()). I can make a PR either way. Mikael > > Garth > > Jacobi and additive_schwarz are the two best preconditioners for a momentum > solve in Navier-Stokes and I don’t think they should have been removed > without even making the ChangeLog. > >> >> The demand for the wrapping comes from the requirement of having >> certain amount of control portable across backends. Is this requirement >> getting abandoned, or at least weakened? > > Another issue is that most users will simply print > list_krylov_solver_preconditioners, and they will then not know that they can > actually create a jacobi preconditioner. If they do find out they will have > to do something (not portable across backends) like > > p = PETScPreconditioner(‘jacobi’) > solver = PETScKrylovSolver(‘cg’, p) > > where they used to be able to do > > solver = KrylovSolver(“cg”, ‘jacobi’) > > Not much more complex, but certainly not very user-friendly to hide > preconditioners like this. > > > > >> >> Jan >> >>> >>> You can control the PETSc preconditioners via PETSc options. This >>> gives you far greater control, makes DOLFIN code simpler and provides >>> greater consistency when using PETSc solver. There will be more >>> changes in DOLFIN 1.7 to give greater control over preconditioning. > > Ok, what are actually the plans for 1.7? > > Mikael > > >>> >>> Garth >>> >>> >>> >>> >>>> Best regards >>>> >>>> Mikael >>>> >>>> _______________________________________________ >>>> fenics mailing list >>>> fenics@fenicsproject.org <mailto:fenics@fenicsproject.org> >>>> http://fenicsproject.org/mailman/listinfo/fenics >>>> <http://fenicsproject.org/mailman/listinfo/fenics>
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