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NDSolve is really slow in version 8 but not 7

• To: mathgroup at smc.vnet.net
• Subject: [mg126036] NDSolve is really slow in version 8 but not 7
• From: Jonathan Frazer <J.Frazer at sussex.ac.uk>
• Date: Fri, 13 Apr 2012 04:53:22 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

Hi All,

I'm using NDSolve to solve a set of roughly 40 first order differential equations. It takes about 10 seconds in version 7 but more like 850 in version 8. Does anyone know why this might be and how I can speed things up?

Also for one scenario I'm getting the error

NDSolve::"ndsz" :  ""At "\[NoBreak]t\[NoBreak]" == "\[NoBreak]39.77534338386624`\[NoBreak]", step size is \
effectively zero; singularity or stiff system suspected."

I realise its difficult to help without me giving an example but its a bit tricky to do so. Are there any standard tricks I could try?

Many thanks,

Jonny