"This email box gets piled up..."
As a point of encouragement and appreciation, this is a sign of a much-used product that people are applying to increasingly-sophisticated research. Best, Peter. Peter G. Raeth, Ph.D. Senior Staff Scientist Signal and Image Processing High Performance Technologies, Inc 937-904-5147 praeth at hpti.com<mailto:praeth at hpti.com> ________________________________ From: petsc-users-bounces at mcs.anl.gov [petsc-users-bounces at mcs.anl.gov] on behalf of Ryan Yan [[email protected]] Sent: Thursday, April 07, 2011 9:49 AM To: PETSc users list Subject: Re: [petsc-users] about pclu Dear Jed, Sorry for late reply. This email box gets piled up... :-) I agree that solves are faster than factorization and GMRES use more MatVecMult, even with exact preconditioner. So I guess PREONLY is meaning direct solve without forming any sub-space and just one forward and backward substitutions? Thanks, Yan On Wed, Apr 6, 2011 at 1:43 AM, Jed Brown <jed at 59a2.org<mailto:jed at 59a2.org>> wrote: On Wed, Apr 6, 2011 at 05:27, Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>> wrote: There should be no difference since direct solves take so long. That is, solves are very fast compared to factorization. If you just want to check the residual, Richardson is cheaper than GMRES because it will require one fewer preconditioner/matrix applications. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110407/946e4fd1/attachment.htm>
