[pydstool-users] simulation with many auxiliary equations

[gyro f. <gyr...@gm...>]

Hi,

I am a newbie with PyDSTool and would appreciate your advice on how
to solve a large system of ODEs that also contains a lot of
auxiliary equations that define and scale variables and parameters.

Here is a small example that illustrates the sort of problem I am
trying to solve:


state variables
---------------
y1, y2, y3

parameters
----------
a1,a2,a3
b1,b2,b3
c1,c2,c3
d1,d2,d3

conversion equations
--------------------
s1 = a1/b1
s2 = a2/b2
s3 = a3/b3
z1 = y1/c1
z2 = y2/c2
z3 = y3/c3

differential equations
----------------------
dy1/dt = s1*z1 - s2*dy2/dt
dy2/dt = s3*z1 - s4*z3
dy3/dt = s2*z3 - s3*z2*dy1/dt

initial conditions
------------------
y1(0) = d1
y2(0) = d2
y3(0) = d3


The examples included in the documentation and distribution are
helpful, but I am unclear on how to specify this system most
efficiently. I am also not clear on when symbolic variables can be
used or if they would help in this instance.

Thank you very much.

Kind regards,
gyro