Re: Nonlinear CG

Hi Ben,

I'm not an expert of non-linear solvers.  Most things I have seen (a 
while ago) were approximated Newton schemes with Jacobi matrix was 
approximated from the operator.  This requires (I think) that one has a 
matrix representation of the operator which I'm afraid you probably 
don't.

Regarding pseudocode or free software I would need to search too.

Best Regards,
Peter

On 09.01.2007, at 18:38, Ben FrantzDale wrote:

> Peter,
> Interesting. I'll start thinking about it.
>
> I think most nonlinear CG flavors require one additional concept: a 
> function,
>   func(const vector& x, scalar& result, vector& result_gradient),
> which computes f(x) and f'(x).
>
> I actually don't want to use PETSc data. My state vector represents 
> atom positions as well as continuum displacements, stored separately, 
> so basically it's a heterogeneous mess. (This is part of the reason a 
> generic approach seems so appealing – I should be able to abstract 
> that heterogeneity away.)
>
> Do you know where I might find pseudocode (or just Free code) for of 
> algorithm?
>
> —Ben
>
>
> On 1/9/07, Peter Gottschling < [email protected]> wrote:Dear Ben,
>>
>> As far as I know, non-linear solvers does not exist in ITL.  It is an
>> excellent idea and we will likely work on it in the future.  If you
>> want to work on this, I'd be happy to support you.
>>
>> I don't know if that helps you, I've written an interface between 
>> PETSc
>> and parallel BGL so that one can read out parallel PETSc matrices from
>> generic libraries and also access to distributed PETSc vector without
>> copying them.  However, it sounds more that you want to use PETSc data
>> with in a clearer way than I did. ;-)
>>
>> Best Regards,
>> Peter
>>
>> On 09.01.2007, at 18:01, Ben FrantzDale wrote:
>>
>> > Dear ITL-devel,
>> > I'm glad I finally found ITL. It looks like it could be the Right 
>> Way
>> > to solve a bunch of problems that various closed-source Fortran
>> > libraries have attempted.
>> >
>> > I am interested in solving large nonlinear minimization problems in
>> > parallel. Presently we are experimenting with several CG solvers. 
>> The
>> > work, but all of them want to see the state vector as a single
>> > contiguous array of doubles. The ITL example using PETSc in parallel
>> > makes me think there are interesting possibilities for large 
>> nonlinear
>> > problems as well.
>> >
>> > The ITL distribution includes two nonlinear examples, but all of the
>> > solvers appear to be linear. Has anyone extended ITL to do nonlinear
>> > minimization?
>> >
>> > Again, great work.
>> >
>> > Thanks,
>> > Ben FrantzDale_______________________________________________
>> > This list is archived at 
>> http://www.osl.iu.edu/MailArchives/mtl-devel/
>> ------------
>> Peter Gottschling, Ph.D.
>> Research Associate
>> Open Systems Laboratory
>> Indiana University
>> 135 Lindley Hall
>> Bloomington, IN 47405
>> Tel.: +1-812-855-3608   Fax: +1-812-856-0853
>> http://www.osl.iu.edu/~pgottsch
>>
>>
>> _______________________________________________
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> _______________________________________________
> This list is archived at http://www.osl.iu.edu/MailArchives/mtl-devel/
------------
Peter Gottschling
Research Associate
Open Systems Laboratory
Indiana University
135 Lindley Hall
Bloomington, IN 47405
Tel.: +1-812-855-3608   Fax: +1-812-856-0853
http://www.osl.iu.edu/~pgottsch

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