Right, providing this "list of times" as a user provided function (not as an
array of doubles) is a more general and better interface. I have no problem
with that. (Note that one's provided function could simple access values in an
array as appropriate :-), so Sean and my simple case are also supported.
Barry
On Dec 10, 2012, at 11:59 PM, Shri <abhyshr at mcs.anl.gov> wrote:
> I think Jed is right. Rather than giving a list of times, it is better to
> provide user-defined callback function (or functions?) for detecting the
> non-smoothness or hitting a time before ts->final_time. MATLAB Ode solvers
> call these discontinuities as 'EVENTS' and provide callback functions to
> detect them. http://www.mathworks.com/help/matlab/ref/ode23.html.
>
> In the power grid project that I'm involved in, there can be three
> possibilities (could be more) when the DAE integrator needs to be stopped.
>
> i) An exogenous event such as a random disturbance at a given prespecified
> time.
> ii) The removal of this disturbance at another prespecified time. (only for
> analysis)
> iii) The removal of this disturbance due to some switching (switch on/off)
> based on threshold crossing (the threshold crossing and switching action
> could be at the same time or delayed).
> iv) Some switching action due to abnormal conditions.
>
> Later on in the project, we will be passing the states from TS at the end of
> each time step to a commercial software that decides the switching logic and
> passes the switching times back to TS PostStep() interface. Thus, there could
> be a need of stopping TS based on the switching times.
>
> Another example of event detection is in circuit simulation where in the zero
> crossing of the waveform needs to be detected.
>
> I think having callback functions for 'EVENTS' would be the right approach.
>
> I recently requested for a couple of features in TS and Jed, Barry, and Emil
> kindly :) agreed
> i) The feature of hitting the exact time has been added to the adaptive
> time-step controller and can be accessed via -ts_exact_final_time MATCHSTEP.
> Note that this is not available with methods that don't use an adaptive
> controller.
> ii) TS can be stopped at any given time via TSPostStep() by calling
> TSSetConvergedReason() with the flag TS_CONVERGED_USER.
>
> Shri
> On Mon, Dec 10, 2012 at 8:36 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> I'd the ability to provide to TS a list of times at which I'd like the ODE
> integrator have exactly match that time on a time-step (that is adjust the
> delta t near that time to hit it exactly). This is something Shri needs.
>
> Is this general enough to add to the library itself? He can write an adaptive
> controller that hits any times he wants.
>
> As a library feature, I'd be more interested in having a controller that
> attempted to hit the zeros of a user-provided functional (because that could
> be used for other forms of model nonsmoothness).
>
>
