[Trilinos-Users] Teuchos::SerialDenseSolver equilibration: unexpected behavior

[Thornquist, Heidi K]

Thanks Nico,  I'm taking care of this right now.

Heidi

-- 
Heidi K. Thornquist
Senior Member of Technical Staff
Electrical Systems Modeling
Sandia National Laboratories
P.O. Box 5800, MS 0316
Albuquerque, NM  87185-0316
Phone: (505)284-8426
Fax:   (505)284-5451






On 10/20/11 5:24 AM, "Nico Schlömer" <nico.schloemer at ua.ac.be> wrote:

> > ============= *snip* =============
> > if (ierr1!=0)
> > return(ierr1);
> > else
> > return(ierr);
> >
> > // one never gets here
> > if (equilibrate_) ierr1 = unequilibrateLHS();
> > return(ierr1);
> > }
> > ============= *snap* =============
>
>Also, this is most likely what Amesos2 devs are working around in
>Amesos2_Lapack_def.hpp:173.
>
>Cheers,
>Nico
>
>
>
>On 10/20/2011 01:14 PM, Nico Schlömer wrote:
>> Problem solved.
>>
>> There is a bug in the Teuchos::Serial*DenseSolver: The unequilibration
>> was actually carried out on the *RHS* whereas it should be the LHS. This
>> basically means that the equilibration never worked if there was a
>> column scaling.
>>
>> Patch attached.
>>
>> I also noticed that in the respective solve() methods, the equilibration
>> is never automatically done:
>>
>> ============= *snip* =============
>> if (ierr1!=0)
>> return(ierr1);
>> else
>> return(ierr);
>>
>> // one never gets here
>> if (equilibrate_) ierr1 = unequilibrateLHS();
>> return(ierr1);
>> }
>> ============= *snap* =============
>>
>> -- I guess the maintainer may want to have a look at this.
>>
>> Cheers,
>> Nico
>>
>>
>>
>> On 10/19/2011 03:45 PM, Nico Schlömer wrote:
>>> Hi,
>>>
>>> I just encountered a rather odd behavior of Teuchos::SerialDenseSolver
>>> when used with equilibration.
>>> After building a specific 3x3 equation system (code attached), I call
>>>
>>> solver.solve();
>>>
>>> without equilibration and get the output
>>>
>>> ================ *snip* ================
>>> WARNING! SerialDenseSolver<T>::solve: System should be equilibrated!
>>> -0.0416252 0.836261 0.358417
>>> ================ *snap* ================
>>>
>>> This solution is correct. Using
>>>
>>> solver.equilibrateMatrix();
>>> solver.equilibrateRHS();
>>> solver.solve();
>>> solver.unequilibrateLHS();
>>>
>>> however, produces
>>>
>>> ================ *snip* ================
>>> -0.0416252 0.653305 0.323626
>>> ================ *snap* ================
>>>
>>> I guess I must be making some sort of mistake here but I fail to see
>>> what the issue could be.
>>> The comments in ./packages/amesos2/src/Amesos2_Lapack_def.hpp suggest
>>> that there may be more to it.
>>> Any hints?
>>>
>>> Cheers,
>>> Nico
>>>
>>>
>>> _______________________________________________
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>>> Trilinos-Users at software.sandia.gov
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>>
>>
>>
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>
>
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