[SciPy-user] PyDSTool and SciPy (integrators)

Gabriel Gellner ggellner@uoguelph...
Thu Apr 17 21:35:09 CDT 2008


> >  I think the right return format depends what people want from the
> >  solution. I see two major kinds of problem one might use an ODE solver
> >  for:
> >
> >  * Integrate out to some stopping point and give the values of
> >  dependent and independent variable there.
> >  * Integrate out to some stopping point and give back a representation
> >  of the solution.
> >
> >  (The first case can in principle be obtained by evaluating the second
> >  at the endpoint, but at the cost of replacing O(1) space by O(n)
> >  space.)
> 
> I personally do not find the former very useful, as I almost always
> want to know something about the intermediate points. My understanding
> is the dopri and radau integrators inherently return the whole
> solution, so maybe an additional calling option supporting the former
> usage could just throw everything out but the last point before the
> whole solution gets copied into a numpy object.
> 
I don't think this is true, as far as I understand the dopri codes don't save
anymore than the runge kutta method needs which is a single step, it is up to the
user supplied callback to save any information, so I think you could just
write a callback that after each point checks if the time is the terminal time
and only save that point.

I will try a proof of concept of this.

Gabriel


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