[petsc-users] snes test fails

[Jed Brown]

On Apr 17, 2013 6:25 PM, "Dharmendar Reddy" <dharmareddy84 at gmail.com> wrote:
>
> Sorry, I do not know how the reply went to your id. I replied the usual
way.
>
>
>
> I am solving :  div(grad(V)) = 0  for x  in [0, L]  and V(0) = V1 and
V(L) = V1
>
> I get a solution V(x) = V1 after solving with intial guess V(X) = 0 for x
in (0, L)
>
> Now, what is the user defined ? is it V(X) = 0 ? or V(x) =  V1 ?

Yes, it is the initial guess. SNES Test does not actually solve the problem.

>
> Is the user defined state is V(X) = V1 then it means the Jacobin is
tested after doing a solve first ?
>
> But then, for a linear Poisson problem, The Jacobin should be independent
of V(X). I seem to get correct solution but snes_type test (fails ?) can
you give me some pointers on how to debug this ?

How do you define the function evaluation? Is the Jacobian code really
independent of the state vector? (It should be.)

>
> Thanks
>
>
> On Wed, Apr 17, 2013 at 5:55 PM, Dharmendar Reddy <dharmareddy84 at gmail.com>
wrote:
>>
>> I am confused.
>>
>> I am solving :  div(grad(V)) = 0  for x  in [0, L]  and V(0) = V1 and
V(L) = V1
>>
>> I get a solution V(x) = V1 after solving with intial guess V(X) = 0 for
x in (0, L)
>>
>> Now, what is the user defined ? is it V(X) = 0 ? or V(x) =  V1 ?
>>
>> Is the user defined state is V(X) = V1 then it means the Jacobin is
tested after doing a solve first ?
>>
>> But then, for a linear Poisson problem, The Jacobin should be
independent of V(X). I seem to get correct solution but snes_type test
(fails ?) can you give me some pointers on how to debug this ?
>>
>> Thanks
>> Reddy
>>
>>
>>
>>
>> On Wed, Apr 17, 2013 at 5:36 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>>
>>> Dharmendar Reddy <dharmareddy84 at gmail.com> writes:
>>>
>>> > Hello,
>>> >          I am solving a one dimensional (linear) Poisson equation. I
have
>>> > setup a snes problem using DM object. I am using Dirichlet boundary
>>> > conditons at both ends of the one dimensional domain. For the test
case i
>>> > use the same value for potential at both ends.
>>> >
>>> > I am using DMplex object for the mesh and dof lay out.
>>> >
>>> > If i run the solver, i get a constant potential profile as expected.
>>> > However, If i run the solver with snes_type test
>>> > It is giving an error. what could i have done wrong ?
>>> > Testing hand-coded Jacobian, if the ratio is
>>> > O(1.e-8), the hand-coded Jacobian is probably correct.
>>> > Run with -snes_test_display to show difference
>>> > of hand-coded and finite difference Jacobian.
>>> > Norm of matrix ratio 1.0913e-10 difference 5.85042e-10 (user-defined
state)
>>> > Norm of matrix ratio 0.5 difference 5.36098 (constant state -1.0)
>>> > Norm of matrix ratio 0.666667 difference 10.722 (constant state 1.0)
>>> > [0]PETSC ERROR: --------------------- Error Message
>>> > -----------------------------------
>>> > -
>>> > [0]PETSC ERROR: Object is in wrong state!
>>> > [0]PETSC ERROR: SNESTest aborts after Jacobian test!
>>>
>>> This is what '-snes_type test' is supposed to do.  So you're fine and
>>> your Jacobian is fine at the initial state, but not at the constant
>>> value 1.0 or -1.0.  (That's okay if those are non-physical states,
>>> otherwise your Jacobian evaluation is incorrect.)
>>>
>>> > [0]PETSC ERROR:
>>> >
-----------------------------------------------------------------------
>>> > -
>>> > [0]PETSC ERROR: Petsc Development GIT revision:
>>> > e0030536e6573667cee5340eb367e8213e67d68
>>> > 9  GIT Date: 2013-04-16 21:48:15 -0500
>>> > [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: ./PoisTest on a mpi_rScalar_Debug named
>>> > login2.stampede.tacc.utexas.edu
>>> >  by Reddy135 Wed Apr 17 17:22:02 2013
>>> > [0]PETSC ERROR: Libraries linked from
>>> > /home1/00924/Reddy135/LocalApps/petsc/mpi_rScalar
>>> > _Debug/lib
>>> > [0]PETSC ERROR: Configure run at Tue Apr 16 22:30:58 2013
>>> > [0]PETSC ERROR: Configure options   --download-blacs=1
--download-ctetgen=1
>>> > --download-
>>> > metis=1 --download-mumps=1 --download-parmetis=1
--download-scalapack=1
>>> > --download-supe
>>> > rlu_dist=1 --download-triangle=1 --download-umfpack=1
>>> > --with-blas-lapack-dir=/opt/apps/
>>> > intel/13/composer_xe_2013.2.146/mkl/lib/intel64/ --with-debugging=1
>>> > --with-mpi-dir=/opt
>>> > /apps/intel13/mvapich2/1.9/ --with-petsc-arch=mpi_rScalar_Debug
>>> > --with-petsc-dir=/home1
>>> > /00924/Reddy135/LocalApps/petsc PETSC_ARCH=mpi_rScalar_Debug
>>> > [0]PETSC ERROR:
>>> >
-----------------------------------------------------------------------
>>> > -
>>> > [0]PETSC ERROR: SNESSolve_Test() line 127 in
>>> > /home1/00924/Reddy135/LocalApps/petsc/src/
>>> > snes/impls/test/snestest.c
>>> > [0]PETSC ERROR: SNESSolve() line 3755 in
>>> > /home1/00924/Reddy135/LocalApps/petsc/src/snes
>>> > /interface/snes.c
>>> >  SNESDivergedReason            0
>>> >  Exiting solve
>>> > --
>>> > -----------------------------------------------------
>>> > Dharmendar Reddy Palle
>>> > Graduate Student
>>> > Microelectronics Research center,
>>> > University of Texas at Austin,
>>> > 10100 Burnet Road, Bldg. 160
>>> > MER 2.608F, TX 78758-4445
>>> > e-mail: dharmareddy84 at gmail.com
>>> > Phone: +1-512-350-9082
>>> > United States of America.
>>> > Homepage: https://webspace.utexas.edu/~dpr342
>>
>>
>>
>>
>> --
>> -----------------------------------------------------
>> Dharmendar Reddy Palle
>> Graduate Student
>> Microelectronics Research center,
>> University of Texas at Austin,
>> 10100 Burnet Road, Bldg. 160
>> MER 2.608F, TX 78758-4445
>> e-mail: dharmareddy84 at gmail.com
>> Phone: +1-512-350-9082
>> United States of America.
>> Homepage: https://webspace.utexas.edu/~dpr342
>
>
>
>
> --
> -----------------------------------------------------
> Dharmendar Reddy Palle
> Graduate Student
> Microelectronics Research center,
> University of Texas at Austin,
> 10100 Burnet Road, Bldg. 160
> MER 2.608F, TX 78758-4445
> e-mail: dharmareddy84 at gmail.com
> Phone: +1-512-350-9082
> United States of America.
> Homepage: https://webspace.utexas.edu/~dpr342
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