[petsc-dev] Recover from TS failure

[Mark Adams]

I have added some code in a TS post step method to look at the number of
nonlinear iterations and cut the time step if it took too many SNES
iterations.  That helped but now I want to go one step further and recover
from a failed time step (see appended error message).

How can/should I recover from a SNES failure inside of TS? I could just put
TSSolve in a loop and if TS failed because of the solver, then reduce the
time step and try to recover the state, and try again.

Thoughts?

Thanks,
Mark

Note, this is a direct solver and the linear solver is diverging?  I've
seen the same thing with the maximum its in SNES and failed linesearch.

23 TS dt 0.0025 time 0.1025
    0 SNES Function norm 9.997473571601e+04
    1 SNES Function norm 2.295851692533e-01
  Nonlinear solve did not converge due to DIVERGED_LINEAR_SOLVE iterations 1
[0]PETSC ERROR: --------------------- Error Message
--------------------------------------------------------------
[0]PETSC ERROR:
[0]PETSC ERROR: TSStep has failed due to DIVERGED_NONLINEAR_SOLVE, increase
-ts_max_snes_failures or make negative to attempt recovery
[0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for
trouble shooting.
[0]PETSC ERROR: Petsc Development GIT revision: v3.8-53-ga2d93b2d43  GIT
Date: 2017-10-09 12:56:49 -0400
[0]PETSC ERROR: ./ex48 on a arch-macosx-gnu-O named MarksMac-5.local by
markadams Wed Nov  1 13:17:15 2017
[0]PETSC ERROR: Configure options --with-cc=clang --with-cc++=clang++
COPTFLAGS="-O2 -g -mavx2" CXXOPTFLAGS="-O2 -g -mavx2" FOPTFLAGS="-O2 -g
-mavx2" --download-mpich=1 --download-parmetis=1 --download-metis=1
--download-hypre=1 --download-ml=1 --download-triangle=1
--download-ctetgen=1 --download-p4est=1 --download-fftw --download-mumps=1
--download-scalapack=1 --with-x=0 --download-superlu_dist
--download-superlu --download-ctetgen --with-debugging=0 --download-hdf5=1
PETSC_ARCH=arch-macosx-gnu-O --download-chaco --with-viewfromoptions=1
[0]PETSC ERROR: #1 TSStep() line 4129 in
/Users/markadams/Codes/petsc/src/ts/interface/ts.c
[0]PETSC ERROR: #2 TSSolve() line 4374 in
/Users/markadams/Codes/petsc/src/ts/interface/ts.c
[0]PETSC ERROR: #3 main() line 1161 in /Users/markadams/Codes/mhd/src/ex48.c
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