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 >
