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Re: NDSolve is using Solve?

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  • Subject: [mg117074] Re: NDSolve is using Solve?
  • From: "J.Frazer" <j.frazer at>
  • Date: Wed, 9 Mar 2011 06:58:34 -0500 (EST)
  • References: <>

Ok so I have one idea. I read that restricting the function definition 
to be something like f[x_?NumericQ,y_?NumericQ] can enable you to avoid 
symbolic evaluation, speeding up the calculation by a factor of 10000 or 
so! My issue now is that I have functions that are defined in terms of 
derivatives of other previously defined functions, so I won't be able to 
blindly go through changing the function definitions. I suppose this 
means I will have to rewrite everything which will probably take me a 
couple of days. Given that I'm not even sure if this will work, any 
suggestions at this point would be very much welcome.



On 8 Mar 2011, at 12:17, J.Frazer wrote:

> Hello everyone,
> This is my first time posting so my apologies if I'm going about this 
the wrong way. I'm having the following problem:
> I'm using NDSolve but its not managing to get to the solution even if 
I leave it running over the weekend. If I greatly simplify one of the 
equations I can get a result but in either case I get the error messages
> Solve:: incnst
> Solve:: ifun
> This worries me as if its trying to simplify analytically, presumably 
as the equations becomes more complicated this will become incredibly 
time consuming.
> Do people agree this may be the cause of the long running time? If so, 
is there a way of stopping NDSolve from using Solve?
> Cheers,
> Jonny

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