The default solver is GMRES, which can solve indefinite systems. ================================ Keita Teranishi Scientific Library Group Cray, Inc. keita at cray.com ================================
From: petsc-dev-bounces at mcs.anl.gov [mailto:petsc-dev-boun...@mcs.anl.gov] On Behalf Of Anush Krishnan Sent: Thursday, August 26, 2010 12:08 PM To: petsc-dev at mcs.anl.gov Subject: Re: [petsc-dev] Problem with conjugate gradient solver Message: 2 Date: Tue, 24 Aug 2010 10:56:53 -0500 From: Barry Smith <bsmith at mcs.anl.gov<mailto:bsm...@mcs.anl.gov>> Subject: Re: [petsc-dev] Problem with conjugate gradient solver To: For users of the development version of PETSc <petsc-dev at mcs.anl.gov<mailto:petsc-dev at mcs.anl.gov>>, Victor Eijkhout <eijkhout at tacc.utexas.edu<mailto:eijkhout at tacc.utexas.edu>> Message-ID: <A4C6A1ED-CDE7-4653-8046-C2797AD5AF31 at mcs.anl.gov<mailto:A4C6A1ED-CDE7-4653-8046-C2797AD5AF31 at mcs.anl.gov>> Content-Type: text/plain; charset="us-ascii" Well you are doing nothing wrong. When I run the code I get the same results as you. I dump the matrix into Matlab and it has a negative eigenvalue so the example is wrong. The code is handling it correctly. >> eig(full(Mat_0)) ans = -0.8042 0.1716 0.6489 1.0000 1.0000 1.0000 1.0000 So are you saying that trying to solve the system of equations in the example will always result in divergence? I tried the same program with a different system that I know has a solution, and even that diverges. I get a proper solution if I use the default KSP solver. Anush I am cc:iing Victor who supposedly wrote the original example. Barry Attached is the matrix saved with -mat_view_matlab -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20100826/0e6594f5/attachment.html>
