thank you very much, Barry. I made a misunderstanding about the parameters "ix" and "iy".
Further question is after finishing scatter, the subvector will be redistributed? I mean like matrix, because I get a submatrix, the rows in some processes will become zero, is the subvector the same with the matrix? thanks. Yujie On Fri, Jan 2, 2009 at 11:46 AM, Barry Smith <bsmith at mcs.anl.gov> wrote: > > VecScatter is for this purpose. > > Rational: extracting subparts of vectors for ghost points etc takes place > many times in a simulation; maybe millions. > Thus separating it into a set-up followed by many uses is a worthwhile > optimization. Extracting submatrices occur > much less often in a simulation, maybe tens, hundreds or thousands of times > so it is not worth the extra complexity > of having separate set-up followed by many uses. One could argue that > uniformity of design means we should have > handled matrices with a MatScatter concept to parallel the Vec approach, > but it is too late now :-). > > Barry > > On Jan 2, 2009, at 1:41 PM, Yujie wrote: > > Like MatGetSubMatrix(), whether is there a function to get a subvector in >> parallel mode? I have checked some scatter functios, they don't likely work. >> thanks a lot. >> >> Regards, >> >> Yujie >> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20090102/f941d3d4/attachment.htm>
