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Topic: NDSolve is using Solve?
Replies: 3   Last Post: Sep 12, 2013 11:14 PM

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Posts: 13
Registered: 3/9/11
Re: NDSolve is using Solve?
Posted: Mar 9, 2011 4:22 PM
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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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