[petsc-users] (no subject)

[Matthew Knepley]

On Mon, May 4, 2015 at 2:11 PM, Reza Yaghmaie <reza.yaghmaie2 at gmail.com>
wrote:

>
> Dear PETSC representatives,
>
> I am solving a nonlinear problem with SNESNGMRES and it converges faster
> with less iterations compared to otehr SNES methods. Any idea why that is
> the case?
>

It is impossible to tell with this information.


> Also SNESQN diverges quickly. I tried to use SNESLINESEARCHBASIC for the
> linesearch option and nothing changes.
>

This can happen, especially if your matrix is far from the identity.


> I presume it is using the default SNESQN method. Btw, there are three
> options for QN, as "SNES_QN_LBFGS, SNES_QN_BROYDEN, SNES_QN_BADBROYEN" in
> teh manual. I tried to associate them with SNES however it seems these
> hyphened names don't work there. What am I missing?
>

-snes_qn_scale_type <lbfgs,broyden,badbroyden>

from
http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/SNES/SNESQNSetType.html

   Thanks,

    Matt

Best regards,
> Ray
>



-- 
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
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