On Tue, Nov 1, 2011 at 09:21, Matthew Knepley <knepley at gmail.com> wrote:
> It could be that: > > a) Your system is really ill-conditioned, and the PC is not that good > > b) Your system has a null space, and the initial guess had no component > in it > > c) Your Jacobian is not actually the Jacobian of the system, so the PC > is not good > > d) The FD approximation to the Jacobian action is not good > > When you have so many different possible problems, the right thing to do > is simplify the system until you can narrow down the cause > > a) Run in serial > > b) Shrink the problem > > c) Fully form the Jacobian using -snes_fd > > d) Run with -pc_type lu > We keep a pretty comprehensive list here, I should have linked it: http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#kspdiverged -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111101/5d97375f/attachment-0001.htm>
