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From: MacDonald, Calum (MAT) on 10 Jan 2010 03:30
I am trying to solve an ODE numerically using NDSolve but get a message

" step size is effectively zero; singularity or stiff system suspected."

Can anyone please suggest an otion I can use along with 'Method' to attempt to overcome the problem?

I have tried Method -> "ExplicitRungeKutta" and it doesn't work. What other options are available?

Thanks for any help.


Glasgow Caledonian University is a registered Scottish charity, number SC021474

Winner: Times Higher Education's Widening Participation Initiative of the Year 2009 and Herald Society's Education Initiative of the Year 2009
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From: dh on 11 Jan 2010 05:30


Hi,

the message means that the at some place the solution is changing very

rapidly compared to the rest of the integration range. You may e.g.

split the integration range into several intervalls. You may also try

the option: "StiffnessSwitching".

Anyway, it always helps if you give a simple example.

Daniel



MacDonald, Calum (MAT) wrote:

> I am trying to solve an ODE numerically using NDSolve but get a message

>

> " step size is effectively zero; singularity or stiff system suspected."

>

> Can anyone please suggest an otion I can use along with 'Method' to attempt to overcome the problem?

>

> I have tried Method -> "ExplicitRungeKutta" and it doesn't work. What other options are available?

>

> Thanks for any help.

>

>

> Glasgow Caledonian University is a registered Scottish charity, number SC021474

>

> Winner: Times Higher Education's Widening Participation Initiative of the Year 2009 and Herald Society's Education Initiative of the Year 2009

> http://www.gcal.ac.uk/newsevents/news/bycategory/theuniversity/1/name,6219,en.html

>



From: Mark McClure on 11 Jan 2010 05:31
On Sun, Jan 10, 2010 at 3:30 AM, MacDonald, Calum (MAT)
<C.A.MacDonald(a)gcal.ac.uk> wrote:
> I am trying to solve an ODE numerically using NDSolve but get a message
> "step size is effectively zero; singularity or stiff system suspected."
> Can anyone please suggest an otion I can use along with 'Method' to attempt to
> overcome the problem?

Of course, it's hard to advise without a specific example but, if you
type the word "stiff" into either the Mathematica 7 Documentation
Center or the online documentation center here:
http://reference.wolfram.com/mathematica/guide/Mathematica.html, you
will find a wealth of information on stiffness in ODEs.

Mark McClure

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