Re: [Visualpython-users] vpython and ode solvers

[Hans F. <H.F...@so...>]

Hi Gary,

> I've been wondering if there would be a programming, accuracy, or
> performance benefit to using a fancy ode solver with vpython rather than
> the canonical v = v + F/m * dt especially as the number of objects
> grows.  My thinking was that I could call the solver once per "frame"
> (say, 1/30 sec), solve for all of the variables all at once, and perhaps
> have better accuracy, and perhaps get more objects into the simulation.
>
> I began to experiment with scipy's odeint, and got some demos working.
> I ran across some instabilites that I tracked down, but before going any
> further I thought I'd ask:
>
> Does this seem worth the effort?

We used scipy.integrate.odeint quite successfully (in a teaching context).

> Is there something I haven't considered that dooms this idea?
Not sure. What doesn't work?

> Has someone already done this?
>
> The instablilty I found is related to in the way odeint (LSODA??)
> manages the independent variable.  I'd like to look at other solvers.
Are saying, it takes too large steps?


> Any suggestions?  In particular I'd like to look at a 4th order
> Runge-Kutta solver, but  the only RK4s that I've found are written in
> python.  Does anyone know where there's a python-wrapped C or Fortran RK
> solver?
My feeling is that the solver in odeint is far more sophisticated than a
RK4 solver. However, I would need more information as to what is
'instable' and what you have tried to overcome this.

Cheers,

Hans