optional dense output in ODE step handlers leads to weird results
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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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