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From "Luc Maisonobe (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MATH-439) Refactoring of solvers (package "analysis.solvers")
Date Fri, 19 Nov 2010 07:59:15 GMT

    [ https://issues.apache.org/jira/browse/MATH-439?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12933714#action_12933714
] 

Luc Maisonobe commented on MATH-439:
------------------------------------

Our exception handling is already quite complex now, so I'd rather slow the pace on this and
wait for users feedback before going further.

For DormandPrince, yes, raising the threshold is an appropriate fix. This test belongs to
the non-regression kind, it's not a mandatory threshold defined from earlier precise settings,
so updating it when the code changes is often fair. The problem is that there is no general
relationship between the local error for which we configure a threshold and the global error
we get at the end. This is still a research subject. The test is here mainly as a safety check
to avoid introducing large regression without noticing them.

> Refactoring of solvers (package "analysis.solvers")
> ---------------------------------------------------
>
>                 Key: MATH-439
>                 URL: https://issues.apache.org/jira/browse/MATH-439
>             Project: Commons Math
>          Issue Type: Improvement
>            Reporter: Gilles
>            Priority: Minor
>             Fix For: 3.0
>
>         Attachments: AbstractUnivariateRealSolver.java
>
>
> The classes in package "analysis.solvers" could be refactored similarly to what was done
for package {{optimization}}.
> * Replace {{MaxIterationsExceededException}} with {{TooManyEvaluationsException}}:
> Apart from the class {{MaxIterationsExceededException}} being deprecated, this approach
makes it difficult to compare different algorithms: While the concept of iteration is algorithm-dependent,
the user is probably mostly interested in the number of function evaluations. 
> * Implement the method {{solve}} in the base class ({{UnivariateRealSolverImpl}}) and
define an abstract method {{doSolve}} to be implemented in derived classes. This method would
then use a new {{computeObjectiveFunction}} method that will take care of the counting of
the function evaluations.
> * Remove "protected" fields (the root is unnecessary since it is returned by {{solve}}).
Arguingly the function value is also not very useful (as we know what it should be), except
for debugging purposes (in which case, it might not be a problem to call the function's {{value}}
method once more).
> * Remove the tolerance setter (accuracy) and make the corresponding fields "final".

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