[petsc-users] Divergence when using Line Search

[Barry Smith]

On May 15, 2012, at 4:32 PM, Avery Bingham wrote:

> I have also seen this behavior, and I think this might be related to the scaling of the variables in the nonlinear system.  I am using PETSc through an application of MOOSE which allows for scaling of the variables.  This scaling reduces the chance that the default cubic backtracking line search fails, but it is not reliable on all problems. Would it be possible to get a scaling-independent Line Search Method implemented within PETSc?  

   Citation?

> 
> Thanks,
> Avery Bingham
> 
> 
> 
> 
> 
> 
> 
> 
> Dear Developers,
> 
> I used SNES with LS cubic and basic. In some cases the cubic model can
> stabilised the global convergence BUT in some case it fails while the basic
> model has given better convergence !!!
> 
> The error is as follows:
> .
> .
> .
> 46:   CFL = 3894.09, Nonlinear = 6.9086e-05, Linear = (64,4.54181e-10,1e-05)
>   Linear solve converged due to CONVERGED_RTOL iterations 66
> 47:   CFL = 3921.01, Nonlinear = 6.86117e-05, Linear =
> (66,3.51905e-10,1e-05)
>   Linear solve converged due to CONVERGED_RTOL iterations 64
> 48:   CFL = 3936.79, Nonlinear = 6.83367e-05, Linear =
> (64,4.50959e-10,1e-05)
>   Linear solve converged due to CONVERGED_RTOL iterations 61
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Floating point exception!
> [0]PETSC ERROR: Infinite or not-a-number generated in norm!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Petsc Release Version 3.2.0, Patch 3, Fri Sep 30 10:28:33
> CDT 2011
> [0]PETSC ERROR: See docs/changes/index.html for recent updates.
> [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [0]PETSC ERROR: See docs/index.html for manual pages.
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: ./code on a linux-gnu named baghapour by baghapour Thu Jan
> 5 16:44:14 2012
> [0]PETSC ERROR: Libraries linked from
> /home/baghapour/softs/petsc/linux-gnu-cxx-debug/lib
> [0]PETSC ERROR: Configure run at Wed Nov  9 19:16:47 2011
> [0]PETSC ERROR: Configure options --with-cc=gcc --with-fc=gfortran
> --with-cxx=g++ --download-f2cblaslapack=1 --download-mpich=1
> --with-clanguage=cxx --with-debugging=no --download-parms --download-hypre
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: VecNorm() line 167 in src/vec/vec/interface/rvector.c
> [0]PETSC ERROR: SNESLineSearchCubic() line 581 in src/snes/impls/ls/ls.c
> [0]PETSC ERROR: SNESSolve_LS() line 218 in src/snes/impls/ls/ls.c
> [0]PETSC ERROR: SNESSolve() line 2676 in src/snes/interface/snes.c
> [0]PETSC ERROR: _petsc_NewtonTimeAdvance() line 131 in Newton.cpp
> 
> I am wondering while the basic model can solve the problem but cubic model
> can not.
> Please help me what conditions may leads the above issue in line search.
> 
> Regards,
> BehZad
>