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https://issues.apache.org/jira/browse/MATH-631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13084242#comment-13084242
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Gilles commented on MATH-631:
-----------------------------
Thanks for the neat summary!
{quote}
* (1) Revert part of 1154614, so get the original algorithm back. The other
changes of that commit, that don't change the actual algorith, can stay.
{quote}
Done in revision 1157185.
{quote}
* (2) If we keep the algorithm, earlier detection would be nice. Not sure which
exception to throw in these cases.
** This would result in a single 'if' that detects that the new approximation
is the same as the previous one, and we thus no longer make progress, in which
case we throw the exception earlier, instead of later.
{quote}
+1 (my position in the "07/Aug/11 20:28" post)
As suggested there, the exception could be "MathIllegalStateException" but with
a clear message stating that the algorithm is stuck. Or maybe a new subclass of
it which we could call "NumericalPrecisionException" or even a general-purpose
"ImplementationException".
{quote}
[...] all 3 documentation extensions would be a good idea.
{quote}
+1
About the "new issue", the message string:
{quote}
"illegal state: maximal count (100) exceeded: evaluations"
{quote}
contains everything:
# error type: illegal state
# failure description: maximal count (100) exceeded
# context: evaluations
I proposed to use this approach (combining message items with the "addMessage"
method of "ExceptionContext") in order to reduce the number of messages in the
"LocalizedFormats" enum. Too many of them are just slight variations on a same
theme.
> "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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