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https://issues.apache.org/jira/browse/MATH-631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13080689#comment-13080689
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Gilles commented on MATH-631:
-----------------------------

How can it be correct to have an infinite loop?
The problem is not slow convergence, which you can overcome by allowing more 
iterations.
It is too low function value accuracy which you cannot overcome by allowing 
more iterations. Thus my point: We must raise the appropriate exception (the 
doc for which will state that it can happen if the function value accuracy is 
too low for the implementation to provide a result).


> "RegulaFalsiSolver" failure
> ---------------------------
>
>                 Key: MATH-631
>                 URL: https://issues.apache.org/jira/browse/MATH-631
>             Project: Commons Math
>          Issue Type: Bug
>            Reporter: Gilles
>             Fix For: 3.0
>
>
> The following unit test:
> {code}
> @Test
> public void testBug() {
>     final UnivariateRealFunction f = new UnivariateRealFunction() {
>             @Override
>             public double value(double x) {
>                 return Math.exp(x) - Math.pow(Math.PI, 3.0);
>             }
>         };
>     UnivariateRealSolver solver = new RegulaFalsiSolver();
>     double root = solver.solve(100, f, 1, 10);
> }
> {code}
> fails with
> {noformat}
> illegal state: maximal count (100) exceeded: evaluations
> {noformat}
> Using "PegasusSolver", the answer is found after 17 evaluations.

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