[SciPy-user] integrating a system of differential equations

ms devicerandom@gmail....
Wed May 27 10:30:56 CDT 2009


Hi Josh,

Joshua Stults ha scritto:
> Massimo,
> 
> If you're having stability problems, usually going to an implicit
> integration scheme will help.  Looks like the scipy.integrate.ode
> class lets you choose an integration scheme based on backward
> difference formulas, which should be unconditionally stable.  

Oh, good.

>You'll
> just need to supply a system function and a Jacobian function.

This is quite unclear to me. That is:
- A single function should calculate the whole system? This is what is
done of course, with each dy(j)/dt saved in a vector at index j for
every j-th equation; but I am not sure it is doable in the way ode wants
it -because I really don't understand how ode wants stuff.

- As for the Jacobian, I'm lost. If it is the matrix described here:

http://en.wikipedia.org/wiki/Jacobian_matrix

I don't understand, looks redundant -it seems in my case it will be a
vector of all my derivatives as a function of t (there are no other
variables I'm integrating) -but isn't it the output of the above
function? But it is all really new stuff for me, sorry.

thanks,
m.


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