[SciPy-User] Why does scipy.integrate.odeint still provide a result even after "repeated convergence failures"?

[Brian Merchant]

Hi Sturla,

I am using fixed parameters. However, the parameters interact non-linearly
with other parameters and the phase variables (for example, via Hill
functions).

I have implemented this system of ODEs in scipy.integrate.odeint without
issue. This is a second implementation that has been rewritten from scratch
so that I could clean up the supporting code.

Kind regards,
Brian

On Tue, May 12, 2015 at 5:36 AM, Sturla Molden <sturla.molden at gmail.com>
wrote:

> Are you trying to fit an ODE or just solve an ODE with known parameters?
>
> Fitting parameters by solving an ODE can be a notoriously difficult
> problem with respect to convergence. There are methods such as "multiple
> shooting" which can improve the situation. But fitting an ODE is often
> an ill-posed problem.
>
>
> Sturla
>
>
>
> On 12/05/15 07:44, Brian Merchant wrote:
> > Hi Warren,
> >
> > Just an update: I was able to "zero" in on the portion of the model that
> > causes the issue (I set the ode function to just return 0 for every
> > other variable, except the one that causes issues).
> >
> > I can't find an error in the Python code responsible for calculating the
> > derivative for that variable (I stepped through it, it simply implements
> > a Hill equation:
> > http://en.wikipedia.org/wiki/Hill_equation_%28biochemistry%29), and the
> > results provided by odeint in the end don't  seem *obviously*
> out-of-whack.
> >
> > Brian
> >
> > On Mon, May 11, 2015 at 9:52 PM, Warren Weckesser
> > <warren.weckesser at gmail.com <mailto:warren.weckesser at gmail.com>> wrote:
> >
> >
> >
> >     On Tue, May 12, 2015 at 12:43 AM, Brian Merchant
> >     <bhmerchant at gmail.com <mailto:bhmerchant at gmail.com>> wrote:
> >
> >         Hi all,
> >
> >         Why does scipy.integrate.odeint still provide a result even
> >         after "repeated convergence failures"? Is this result still of
> use?
> >
> >
> >
> >     Which version of scipy are you using?  Can you give a short example
> >     that demonstrates the problem?
> >
> >     Warren
> >
> >
> >         Kind regards,
> >         Brian
> >
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