On Fri, Mar 16, 2012 at 8:40 AM, Klaij, Christiaan <C.Klaij at marin.nl> wrote:
> The manual page 87 states that "there are several variants > of the Schur complement preconditioner obtained by dropping some > of the terms, these can be obtained with > -pc_fieldsplit_schur_factorization_type <diag,lower,upper,full>" > > 1) What is (will be) the name of the corresponding function? > There isn't one. > 2) It would be nice to know what exactly is being dropped. <full> > is obvious and apparently <diag> drops the right most matrix, but > what do lower and upper drop? > http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/PC/PCFIELDSPLIT.html > 3) I'm confused about the minus sign in the <diag> form and its > motivation. It doesn't come from the factorization. Is the rhs > multiplied with a minus sign as well? Why not follow the sign > convention of Elman's taxonomy (eq 3 and 4, JCP 227, 2008)? > It makes the PC positive definite. Matt > > dr. ir. Christiaan Klaij > CFD Researcher > Research & Development > E mailto:C.Klaij at marin.nl > T +31 317 49 33 44 > > MARIN > 2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands > T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl > > -- 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120316/f8efb6da/attachment-0001.htm>
