problem with -snes_mf_operator option

[Matthew Knepley]

I am not sure what is going on with your code, but I have just tested an example
and it works. I recommend you try

  cd src/snes/examples/tutorials
  make ex5
  ./ex5 -snes_monitor -snes_view
  ./ex5 -snes_monitor -snes_view -snes_mf
  ./ex5 -snes_monitor -snes_view -snes_mf_operator

  Thanks,

     Matt

On Wed, Mar 26, 2008 at 4:14 PM, Vijay S. Mahadevan <vijay.m at gmail.com> wrote:
> Hi all,
>
>  I have a nonlinear solver test code that can use a user specified
>  Jacobian function directly, set using SNESSetJacobian. Now if I use
>  -snes_mf option, the solution scheme depends only on the residual and
>  the convergence is equivalent to the case when using the real Jacobian
>  matrix itself. But if I try the -snes_mf_operator option, with the
>  Jacobian=NULL to start with and the preconditioner being correctly
>  allocated the memory needed, I end up with a NULL argument exception.
>  I also alternately set the preconditioner to Identity matrix in order
>  to avoid any problems from user code to trickling in, but to no avail.
>
>  Here's the call stack.
>
>  [0]PETSC ERROR: Null argument, when expecting valid pointer!
>  [0]PETSC ERROR: Null Object: Parameter # 1!
>  [0]PETSC ERROR:
>  ------------------------------------------------------------------------
>  [0]PETSC ERROR: Petsc Release Version 2.3.3, Patch 7, Fri Oct 26
>  14:21:35 CDT 2007 HG revision:
>  2e223033ba960114833e1f9713ab393ec78c056f
>  [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: bin/test-dbg on a linux-gnu named grove by vijaysm Wed
>  Mar 26 16:06:45 2008
>  [0]PETSC ERROR: Libraries linked from
>  /state/partition1/local/petsc-2.3.3-p7/lib/linux-gnu-c-debug
>  [0]PETSC ERROR: Configure run at Fri Nov  9 15:02:46 2007
>  [0]PETSC ERROR: Configure options --with-cc=gcc --with-fc=ifort
>  --with-cxx=g++ --download-f-blas-lapack=1 --download-mpich=1
>  --with-shared=1
>  [0]PETSC ERROR:
>  ------------------------------------------------------------------------
>  [0]PETSC ERROR: PetscObjectGetComm() line 34 in src/sys/objects/gcomm.c
>  [0]PETSC ERROR: VecNormBegin() line 495 in src/vec/vec/utils/comb.c
>  [0]PETSC ERROR: MatMFFDCompute_WP() line 73 in src/mat/impls/mffd/wp.c
>  [0]PETSC ERROR: MatMult_MFFD() line 294 in src/mat/impls/mffd/mffd.c
>  [0]PETSC ERROR: MatMult() line 1632 in src/mat/interface/matrix.c
>  [0]PETSC ERROR: PCApplyBAorAB() line 584 in src/ksp/pc/interface/precon.c
>  [0]PETSC ERROR: GMREScycle() line 159 in src/ksp/ksp/impls/gmres/gmres.c
>  [0]PETSC ERROR: KSPSolve_GMRES() line 241 in src/ksp/ksp/impls/gmres/gmres.c
>  [0]PETSC ERROR: KSPSolve() line 379 in src/ksp/ksp/interface/itfunc.c
>  [0]PETSC ERROR: SNES_KSPSolve() line 2578 in src/snes/interface/snes.c
>  [0]PETSC ERROR: SNESSolve_LS() line 184 in src/snes/impls/ls/ls.c
>  [0]PETSC ERROR: SNESSolve() line 1871 in src/snes/interface/snes.c
>
>  From what I can understand from the PETSc code (snes.c, mffd.c), the
>  current_u for MFFD context is NULL here. And that is the reason for
>  the final exception. But I do not understand how this can be since it
>  works perfectly fine with -snes_mf option with no changes in the code.
>
>  Please do let me know if you think I should specifically be looking
>  for something to tackle this issue. Any help will be appreciated.
>
>  Thanks,
>  Vijay
>
>



-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which
their experiments lead.
-- Norbert Wiener