[jira] [Resolved] (MATH-604) optional dense output in ODE step handlers leads to weird results

["Luc Maisonobe (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/MATH-604?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Luc Maisonobe resolved MATH-604.
--------------------------------

    Resolution: Fixed

Fixed in subversion repository as of r1139831

> optional dense output in ODE step handlers leads to weird results
> -----------------------------------------------------------------
>
>                 Key: MATH-604
>                 URL: https://issues.apache.org/jira/browse/MATH-604
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 2.2
>            Reporter: Luc Maisonobe
>            Assignee: Luc Maisonobe
>             Fix For: 3.0
>
>
> The requiresDenseOutput method defined in the StepHandler interface was first created as an optimization feature to avoid calling computeDerivatives too many times for some integrators. In fact, only Dormand-Prince 8 (5,3) needs it because we can save 3 calls per step when the interpolator is not used.
> This feature brings more problems than it solves:
> * it forces users to implement this method despite its purpose is not clear,
> * even if the method returns false, sometimes dense output will be generated (in fact when there are events detectors),
> * it creates problems with at least Gragg-Bulirsch-Stoer since this integrator really needs interpolation,
> * it will create the same problems for Adams integrators (they also need interpolation),
> * this "optimization" is useful only for one integrator: Dormand-Prince 8 (5,3),
> * in many cases, even for Dormand-Prince 8 (5,3) it does not optimize anything since people will often need interpolation
> So I would like to completely remove this.
> Removing the method is backward compatible for users.

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