[petsc-users] A number of questions about DMDA with SNES and Quasi-Newton methods

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>> On Oct 3, 2017, at 5:54 AM, zakaryah . <zakaryah at gmail.com> wrote:
>> 
>> I'm still working on this.  I've made some progress, and it looks like the issue is with the KSP, at least for now.  The Jacobian may be ill-conditioned.  Is it possible to use -snes_test_display during an intermediate step of the analysis?  I would like to inspect the Jacobian after several solves have already completed,
>
>    No, our currently code for testing Jacobians is poor quality and poorly organized. Needs a major refactoring to do things properly. Sorry

You can use -snes_compare_explicit or -snes_compare_coloring to output differences on each Newton step.