[petsc-users] (no subject)

[Reza Yaghmaie]

Dear Matt,

Actually the initial jacobian was identity. Regular SNES converges in 48
iterations, GMRES in 19, NCG in 67,...
Do you think SNESQN with the basiclineseach was the problem for divergence?
If I use SNESQN by default should not it converge with initial identity
jacobian?

Best regards,
Reza




On Monday, May 4, 2015, Matthew Knepley <knepley at gmail.com> wrote:

> On Mon, May 4, 2015 at 2:11 PM, Reza Yaghmaie <reza.yaghmaie2 at gmail.com
> <javascript:_e(%7B%7D,'cvml','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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20150504/9586f915/attachment-0001.html>