[petsc-users] SNESQN number of past states

[Smith, Barry F.]

  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

  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
>