Hi, Hong and Barry, Thanks a lot. Have a nice day. Zhengyong
On Tue, May 31, 2011 at 9:48 PM, Barry Smith <bsmith at mcs.anl.gov> wrote: > > With petsc-dev > http://www.mcs.anl.gov/petsc/petsc-as/developers/index.html there are very > easy ways to solve the Schur complement systems using PCFIELDSPLIT see > http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-dev/docs/manualpages/PC/PCFIELDSPLIT.html > > > Barry > > > On May 31, 2011, at 2:41 PM, Hong Zhang wrote: > > > This is virtually SCHUR complement. You may take a look at > > petsc-dev/src/ksp/ksp/examples/tests/ex11.c and > > petsc-dev/src/ksp/ksp/examples/tests/makefile: runex11 > > > > Hong > > > > On Tue, May 31, 2011 at 8:29 AM, RenZhengYong <renzhengyong at gmail.com> > wrote: > >> I have a linear system of equation like > >> [A B] [E]= [C] > >> [F G] [S]= [D], > >> where size of matrix A is NxN, B is NxNs, F is Ns_N, G is Ns_Ns; size of > >> vector E is N, S is Ns, C is N and D is N. > >> Instead of solving them together, I prefer to solve it by: > >> (1) AX=B, AY=C; > >> (2) QS=P, Q= G-FX, P=D-FY, > >> due to the dense property of G. > >> > >> In step (1), I need to extract a new "vec" Bi from "mat" B, according to > the > >> way of PETSc telling me. My question is that could I do it as follows, > >> for a given sparse matrix B, first get transpose of B by > "MatTranspose(B, > >> MatReuse, B_t); then, form a new "vec" Bi by "MatGetRow(...)"? > >> If answer is yes, is it expensive? > >> > >> > >> > >> > >> -- > >> Zhengyong Ren > >> AUG Group, Institute of Geophysics > >> Department of Geosciences, ETH Zurich > >> NO H 47 Sonneggstrasse 5 > >> CH-8092, Z?rich, Switzerland > >> Tel: +41 44 633 37561 > >> e-mail: zhengyong.ren at aug.ig.erdw.ethz.ch > >> Gmail: renzhengyong at gmail.com > >> > > -- Zhengyong Ren AUG Group, Institute of Geophysics Department of Geosciences, ETH Zurich NO H 47 Sonneggstrasse 5 CH-8092, Z?rich, Switzerland Tel: +41 44 633 37561 e-mail: zhengyong.ren at aug.ig.erdw.ethz.ch Gmail: renzhengyong at gmail.com -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110601/239a7a6f/attachment.htm>
