[petsc-users] DIVERGED_FNORM_NAN

[Barry Smith]

> On Sep 16, 2015, at 8:28 AM, Alexander Lindsay <adlinds3 at ncsu.edu> wrote:
> 
> Hi all,
> 
> I've built a MOOSE application and the problem I'm studying solves great using serial LU. However, when I try to solve in parallel using super LU, I encounter many DIVERGED_LINE_SEARCH errors using the default bt line search. If I switch to line_search=none, then instead of DIVERGED_LINE_SEARCH errors I get DIVERGED_FNORM_NAN errors. I do not have a lot of debugging experience, but I am slowly gaining more. Is there a good way to get more information about what's causing the NAN's? I.e. a specific residual or jacobian statement?
> 

   It would be useful to have full output with -snes_monitor -snes_converged_reason -snes_linesearch_monitor -ksp_monitor_true_residual -ksp_converged_reason

   The original DIVERGED_LINE_SEARCH is almost always an indication that the step direction is not a Newton step. This needs to be debugged see http://www.mcs.anl.gov/petsc/documentation/faq.html#newton   Switching to no line search is not a useful thing to do here.

  Barry


> This may not even be an appropriate list to post this problem in (could be more on the MOOSE side); apologies if that's the case.
> 
> Alex