[petsc-users] SNESQN number of past states

[Matthew Knepley]

On Wed, Feb 14, 2018 at 6:43 PM, Smith, Barry F. <bsmith at 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/939b553f045c5ba32242d0d49e80e4934ed3bf76/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 <bikash at 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/>
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