Re: [ojAlgo-user] QuadraticSolver with unsatisfiable constraints

[Anders P. <an...@op...>]

Can you perhaps give me 2 test cases; 1 for the NPE case and 1 for the  
incorrect state case. /Anders


On 16 nov 2009, at 14.33, Pierre AUSLAENDER wrote:

>
> Hello Anders,
>
> Thanks a lot for the swift reply.
>
> I 've played with the latest snapshot and here are my findings:
> - Most of the times now, when the constraints cannot be satisfied,  
> the solver terminates with the state FAILED, which is what one would  
> expect, albeit after a great lot of iterations.
> - Sometimes however, it terminates with the state OPTIMAL, and the  
> model validation returns FALSE, same as before I took the snapshot.
> - Sometimes as well, it throws a NPE in the SVD (after saying that  
> LU is not solvable).
>
> I'm trying to build a simple JUnit and send it to you.
>
> Kind regards,
> Pierre
>
>
>
> "Anders Peterson" <an...@op...>
> 16.11.2009 12:57
> Please respond to
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> Re: [ojAlgo-user] QuadraticSolver with unsatisfiable constraints
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> On 16 nov 2009, at 11.06, Pierre AUSLAENDER wrote:
>
> > Hello,
> >
> > Thank you for this library, which is a joy to use - once I got over
> > the lack of documentation.
> >
> > I'm using the QuadraticSolver (ActiveSetSolver) on a least squares
> > minimisation problem, under a set of linear constraints. When the
> > constraints can be satisfied, it works perfectly. However, when the
> > constraints cannot be satisfied, the solver still returns with an
> > OPTIMAL state after a few iterations. I was puzzled until I
> > discovered the QuadraticSolver.validateSolution(...) methods, which
> > I can use to effectively test the solution against the constraints.
> >
> > Is this the way it is supposed to work, or did I do something wrong?
> > I would have expected the solver to FAIL instead.
>
>
> I recently fixed a couple of bugs related to this. Get the latest
> snapshot download from Source Forge, and try if that solves your
> problem. If it doesn't I'd like you to give me (junit) test case.
>
>
> > As an aside question, there is the following JavaDoc comment on
> > ExpressionBasedModel.addConstraint(final String aName, ....): Note
> > that only the first constraint you add will be used by the solver.
> > What does this comment mean? Is it simply related to the uniqueness
> > of the constraint name, or has it wider implications?
>
>
> That comment should have been removed. It was only relevant for the
> now removed/replaced KnapsckSolver. That solver could only use 1
> constraint - the first one you added. I'll correct the javadoc comment
> now.
>
>
> /Anders
>
>
>
> > Thank you,
> > Pierre
> >
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