BTW, the manual page for TSMonitorSet seems to be out-of-date, as compared with the usage in src/ts/examples/tutorials/ex18.c
Rich On 17 Aug 2011, at 15:02, Richard Katz wrote: >> The details depend on the adaptive controller. Unfortunately, we haven't yet >> unified the interface for adaptive controllers, so, for example, TSALPHA and >> TSGL have different APIs. But both of them provide adaptive controllers now >> and the rate of increase can be limited. > > Is there an example showing the use of these controllers? > >> I think having these interfaces is really undesirable and that we should >> unify it, but the information provided by the error estimates for TSGL are >> quite different from most methods (OTOH, they seem to me noisy which limits >> their utility, but there are other possible reasons for that, including >> "starting methods"). > > Is it possible for the user to push a custom controller? I.e. a call-back > that gets passed the SNES converged reason, the last SNES residual, the > current time-step size, the solution vector, etc. > > This would provide an opportunity to apply a CFL condition, customise the > step-size adaptivity. > >> It is obviously important that TS not just chug along without error if a >> timestep fails. >> >> So this is possible, but it's somewhat inconsistent between methods. It >> would help a great deal to build a suite of test problems that provide some >> way to evaluate error (even just through self-convergence) so that we can >> test whether an adaptive method is performing well. > > Perhaps you could do this for the heat equation with harmonic initial data. > >> My intent is to provide some common interface for adaptive controllers as >> well as some sample controllers. The controller can evaluate whether to >> accept or reject a step as well as choosing the next time step and, for the >> variable-order families, the method to use for the next step (selected from >> a list of candidate schemes). This is basically what I did in TSGL and >> later, and what Lisandro did in TSAlpha, but we need to unify the interface >> despite these methods giving us somewhat different information in their >> (embedded or extrapolated) error estimates. > > This sounds great. > >> I think TSAlpha has the best tested adaptive controller right now. Getting >> all the cool adaptive features into TSARKIMEX is next, hopefully with a >> unified interface for user-provided controllers. > > So now that I have TSBEULER working for my problem, should I try to upgrade > to TSALPHA ? > > Cheers, > Rich ________________________________ Richard Foa Katz Dept Earth Sciences, Univ Oxford http://foalab.earth.ox.ac.uk
