On Mon, Jun 8, 2009 at 6:35 PM, Barry Smith<bsmith at mcs.anl.gov> wrote: > > On Jun 8, 2009, at 4:32 PM, Lisandro Dalcin wrote: > >> On Mon, Jun 8, 2009 at 5:52 PM, Barry Smith<bsmith at mcs.anl.gov> wrote: >>> >>> On Jun 8, 2009, at 3:46 PM, Lisandro Dalcin wrote: >>> >>>> Well, all you say that GMRES is not coded for right PC's, however, >>>> after reviewing (in a hurry) the code for GMRES, it seems to handle >>>> right preconditioner. Moreover, I've just tested solving (with SNES) a >>>> steady lid-driven cavity flow in 2d with linear quads using SUPG/PSPG, >>>> default tolerances, default restart, no diag-scaling, starting with >>>> zero nonlinear guess ... >>> >>> ?Does nonzero initial guess work properly? >>> >> >> I've not tested it, but it seems that KSPInitialResidual (called >> inside KSPSolve_GMRES) handles this well. Moreover, the GMRES restart >> itself depends on proper handling of nonzero initial guesses :-) >> >>> >>>> in short, using -ksp_right_pc and just >>>> changing -ksp_type to gmres/fgmres, and ALL the SNES iterates (up to 3 >>>> nonlinear its) and GMRES|FGMRES iterates (64, 169, 177 linear its) are >>>> almost the same (except the last four digits using default KSP >>>> monitor). >>>> >>>> Sorry for the insistence, but ... ?Am I missing something? Do any of >>>> you remember exactly what part of GMRES had problems with right >>>> preconditioning? >>> >>> ?Sadly, no I do not remember the exact issue with right preconditioner; I >>> was thinking it was more or less completely broken. >>> >> >> I'll do a bit more of testing, mainly regarding nonzero initial >> guesses and diagonal scaling. If the outcome of this is that all is >> working ... Do you agree about considering this a regression (from >> 2.3.3) and pushing a fix in release-3.0.0 ? > > ? Fine with me. >
OK, I've confirmed that all work as expected using a nonzero initial guess. Then I re-enabled right preconditioner in GMRES, pushed it to release-3.0.0, and merged in petsc-dev. -- Lisandro Dalc?n --------------- Centro Internacional de M?todos Computacionales en Ingenier?a (CIMEC) Instituto de Desarrollo Tecnol?gico para la Industria Qu?mica (INTEC) Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET) PTLC - G?emes 3450, (3000) Santa Fe, Argentina Tel/Fax: +54-(0)342-451.1594