Hello,
Jira issue MATH-596 <https://issues.apache.org/jira/browse/MATH-596>
shows what seems to me a very old design problem (it dates back to the
Mantissa library, exactly on 2002-12-24!).
The problem is the requiresDenseOutput method declared in the
StepHandler interface. This interface is a user interface (so it cannot
be an abstract class by the way). I think the method should be removed.
Here are the rationale I listed in the comments on the Jira issue:
> This requiresDenseOutput was added long ago (even before this code was
> included in Apache Commons Math) as an optimization to avoid calling
> computeDerivatives too many times for some integrators. In fact, only
> Dormand-Prince 8 (5,3) needs it because if the interpolator is not
> used, we can save 3 calls per step.
>
> Now I think this feature brings more problems than it solves:
>
> it forces users to implement this method despite its purpose is not
> clear, obviously 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
> in many cases, even for this integrator it does not optimize anything
> since people will need interpolation
>
> So I would like to completely remove this.
Removing the method is backward compatible for users.
Any thought about this ?
Luc
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