Thanks Barry and Matthew.
@Barry: I'm following the same procedure as you've mentioned -
PetscOptionsSetValue() precede SNESSetFromOptions. Here's the snippet for
my code:
-----------------------------------------------------------------------------------------------------------
error = SNESCreate(PETSC_COMM_WORLD,&snes);
checkPETScError(error,
"SNESCreate failed.");
error = SNESSetType(snes, SNESQN);
checkPETScError(error,
"SNESSetType failed.");
error = SNESQNSetType(snes, SNES_QN_LBFGS);
checkPETScError(error,
"SNESQNSetType failed.");
error = SNESQNSetScaleType(snes, SNES_QN_SCALE_SHANNO);
checkPETScError(error,
"SNESQNSetScaleType failed.");
error = SNESQNSetRestartType(snes, SNES_QN_RESTART_PERIODIC);
checkPETScError(error,
"SNESQNSetRestartType failed.");
error = PetscOptionsSetValue("-snes_qn_m","500");
checkPETScError(error,
"PETScOptionsSetValue failed.");
SNESLineSearch linesearch;
error = SNESGetLineSearch(snes,&linesearch);
checkPETScError(error,
"SNESGetLineSearch failed.");
error = SNESLineSearchSetType(linesearch,SNESLINESEARCHCP);
checkPETScError(error,
"SNESLineSearchSetType failed.");
error = PetscOptionsSetValue("-snes_linesearch_max_it", "1");
checkPETScError(error,
"PetscOptionsSetValue failed.");
error = SNESLineSearchView(linesearch, PETSC_VIEWER_STDOUT_WORLD);
checkPETScError(error,
"SNESLineSearchView failed.");
error =SNESLineSearchSetMonitor(linesearch,
PETSC_TRUE);
checkPETScError(error,
"SNESLineSearchSet Monitor failed.");
error = SNESLineSearchSetFromOptions(linesearch);
checkPETScError(error,
"SNESLineSearchSetFromOptions failed.");
SNESLineSearchReason lineSearchReason;
error = SNESLineSearchGetReason(linesearch, &lineSearchReason);
checkPETScError(error,
"SNESLineSearchGetReason failed.");
error = SNESSetFunction(snes,r,FormFunction,&petscData);
checkPETScError(error,
"SNESSetFunction failed.");
//
// Customize KSP
//
error = SNESGetKSP(snes,&ksp);
checkPETScError(error,
"SNESGetKSP failed.");
error = KSPSetType(ksp,KSPGMRES);
checkPETScError(error,
"KSPSetType failed.");
error = KSPGMRESSetRestart(ksp,300);
checkPETScError(error,
"KSPGMRESSetRestart failed.");
error = KSPSetInitialGuessNonzero(ksp,PETSC_TRUE);
checkPETScError(error,
"KSPSetInitialGuessNonzero failed.");
error = KSPGetPC(ksp,&pc);
checkPETScError(error,
"KSPGetPC failed.");
error = PCSetType(pc,PCJACOBI);
checkPETScError(error,
"PCSetType failed.");
error = PCSetReusePreconditioner(pc,PETSC_TRUE);
checkPETScError(error,
"PCSetReusePreconditioner failed.");
error = KSPSetTolerances(ksp,
PETSC_DEFAULT,
1e-15,
1e7,
10000);
checkPETScError(error,
"KSPSetTolerances failed.");
error = KSPSetFromOptions(ksp);
checkPETScError(error,
"Call to KSPSetFromOptions() failed.");
//
//get reason for non-convergence
//
KSPConvergedReason kspReason;
error = KSPGetConvergedReason(ksp, &kspReason);
checkPETScError(error,
"Call to KSPGetConvergedReason() failed.");
if(kspReason < 0)
{
if(debugLevel != 0)
std::cout<<"Other kind of divergence in SNES-KSP : "<< kspReason
<<std::endl;
}
PetscInt lag = 1;
error = SNESSetLagPreconditioner(snes,
lag);
checkPETScError(error,
"Call to SNESSetLagPreconditioner() failed.");
PetscInt maxFails = 2;
error = SNESSetMaxLinearSolveFailures(snes,maxFails);
checkPETScError(error,
"Call to SNESSetMaxLinearSolveFailures() failed.");
PetscReal abstol = 1e-13; // absolute convergence tolerance
PetscInt maxit = 100000;
error = SNESSetTolerances(snes,
abstol,
PETSC_DEFAULT,
PETSC_DEFAULT,
maxit,
maxit);
checkPETScError(error,
"SNESSetTolerances failed.");
error = SNESView(snes,
PETSC_VIEWER_STDOUT_WORLD);
checkPETScError(error,
"Call to SNESView() failed.");
error = SNESMonitorSet(snes,SNESMonitorDefault,PETSC_NULL,PETSC_NULL);
checkPETScError(error,
"Call to SNESMonitorSet() failed.");
error = SNESSetFromOptions(snes);
checkPETScError(error,
"Call to SNESSetFromOptions() failed.");
//
// Solve the system
//
error = SNESSolve(snes,PETSC_NULL,x);
checkPETScError(error,
"Call to SNESSolve() failed.");
SNESConvergedReason reason;
error = SNESGetConvergedReason(snes,&reason);
checkPETScError(error,
"Call to SNESGetConvergedReason() failed.");
------------------------------------------------------------------------------------------------------------------------------------
Also, I didn't find any SNESQN examples in my snes/examples folder (using
petsc-3.6.3).
Moreover, the Powell descent condition seems to be only declared and then
assigned a value through the PetscOptionsReal call. Beyond that I didn't
find any other mention of it. I was grepping for powell_downhill variable.
(Note: powell_downhill features in 3.6.3 and not in 3.7 version).
Thanks,
Bikash
On Wed, Feb 14, 2018 at 7:02 PM, Matthew Knepley <knep...@gmail.com> wrote:
> On Wed, Feb 14, 2018 at 6:43 PM, Smith, Barry F. <bsm...@mcs.anl.gov>
> wrote:
>
>>
>> Hmm,
>>
>> 1) make sure you call PetscOptionsSetValue() before you call to
>> SNESSetFromOptions()
>>
>> 2) make sure you call SNESSetFromOptions()
>>
>> 3) did you add a prefix to the SNES object? If so make sure you include
>> it in the PetscOptionsSetValue() call.
>>
>> I can't see a reason why it won't work. Does it work with the PETSc
>> examples for you or not?
>>
>> Regarding the Powell descent option, I'm afraid you'll need to examine
>> the code for exact details. src/snes/impls/qn/qn.c
>
>
> Here is the description
>
> https://bitbucket.org/petsc/petsc/src/939b553f045c5ba32242d0d49e80e4
> 934ed3bf76/src/snes/impls/qn/qn.c?at=master&fileviewer=
> file-view-default#qn.c-451
>
> Thanks,
>
> Matt
>
>
>>
>> Barry
>>
>>
>> > On Feb 14, 2018, at 5:25 PM, Bikash Kanungo <bik...@umich.edu> wrote:
>> >
>> > Hi,
>> >
>> > I'm using the L-BFGS QN solver. In order to set the number of past
>> states (also the restart size if I use Periodic restart), to say 50, I'm
>> using PetscOptionsSetValue("-snes_qn_m", "50"). However while running,
>> it still shows "Stored subspace size: 10", i.e., the default value of 10 is
>> not overwritten.
>> >
>> > Additionally, I would like to know more about the the
>> -snes_qn_powell_descent option. For Powell restart, one uses a gamma
>> parameter which I believe is defined by the -snes_qn_powell_gamma option.
>> What exactly does the descent condition do? It would be useful if there are
>> good references to it.
>> >
>> > Thanks,
>> > Biksah
>> >
>> > --
>> > Bikash S. Kanungo
>> > PhD Student
>> > Computational Materials Physics Group
>> > Mechanical Engineering
>> > University of Michigan
>> >
>>
>>
>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
>
--
Bikash S. Kanungo
PhD Student
Computational Materials Physics Group
Mechanical Engineering
University of Michigan
