[SciPy-user] integrate.odeint , stiff chemical equations and mass conservation -any hint?

Anne Archibald peridot.faceted@gmail....
Tue Jun 2 15:43:24 CDT 2009


2009/6/2 ms <devicerandom@gmail.com>:
> Hi Anne,
>
> Thanks for the suggestions! I didn't know about pydstool and I will
> definitely try it.
>
>> On the other hand, it may be more valuable to keep the total mass as a
>> free parameter so that you can judge the quality of your solutions by
>> looking at how much it varies. After all, the total mass is only one
>> direction in which your approximate solution can deviate from the true
>> solution.
>
> True; however we want to use the model to predict somehow the
> concentrations of species in a chemical system, and if mass is not
> conserved (it goes up like 10 times) such prediction won't look good :)

Indeed not, but it seems to me that there's a risk that enforcing mass
conservation will avoid that problem but then leave you with answers
that are just as wrong but not in an obvious way.

Anne

>> It's also, of course, possible there's a bug in your derivative
>> function - it's worth checking that the derivative vector is always
>> orthogonal to the gradient of mass-as-a-function-of-your-parameters.
>
> Thanks for the hint, I will check it.
>
> m.
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