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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-871) math3 SecantSolver can return Double.INFINITE
Date Mon, 01 Oct 2012 09:27:07 GMT

    [ https://issues.apache.org/jira/browse/MATH-871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13466711#comment-13466711
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Gilles commented on MATH-871:
-----------------------------

bq. In SecantSolver.doSolve(), I had a situation in which f0 and f1, from computeObjectiveValue()
on lines 77 & 78, were the same value.

My first comment was a bit hasty.
"f0" and f1" cannot have the same value, as that would mean that there is no bracketing, a
condition that is checked and, if not satisfied, raises an exception.

The line numbers you refer to seems to indicate that I do not look at the same code: Did you
test with a recent snapshot of the library?
Alternately, please provide the use case.


                
> math3 SecantSolver can return Double.INFINITE
> ---------------------------------------------
>
>                 Key: MATH-871
>                 URL: https://issues.apache.org/jira/browse/MATH-871
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 3.0
>            Reporter: Anthony Maidment
>            Priority: Minor
>
> In SecantSolver.doSolve(), I had a situation in which f0 and f1, from computeObjectiveValue()
on lines 77 & 78, were the same value.
> Then when it calculates the next appromixation at line 101:
> final double x = x1 - ((f1 * (x1 - x0)) / (f1 - f0));
> The denominator is then zero, and the next approximation is Double.INFINITE.
> I was able to work around this in this particular instance by relaxing the accuracy requirements
of the solver, although I haven't yet fully tested the downstream implications of this change.

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