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From Luc Maisonobe <Luc.Maison...@free.fr>
Subject Re: [math] ODE integrator
Date Fri, 05 Jun 2009 18:12:24 GMT
Angelo Port a écrit :
> Hi,
> 
> I am attempting to use the "DormandPrince54Integrator". I have listed the
> implementation steps below:
> 
> 1. Implement my version of the "FirstOrderDifferentialEquations" interface
> with my equations. 
> 2. Initialize my IVP values and called the DR54 integrator
> 
> When I run the integrator, my output always matches my input at each time
> step. I have probed the independent time variable  and it appears to step
> towards my final time as expected. Did I forget a step? Any help or
> suggestions are appreciated.

What you have done should be sufficient.
Could you check your differential equations output non-zero values ?
Could you chekc a simplified set of differential equations like for example

  public void computeDerivatives(double t, double[] y, double[] yDot) {
    Arrays.fill(yDot, 1.0);
  }

Did you check the value at each step using a StepHandler or did you
check only the final values after the integrator run ?
Could you compare your code with the junit test cases that are in the
source tree ?
Could you copy/paste the part of your code corresponding to the
differential equations and the integrator call in a new message to the
list ?

Luc

> 
> Angelo


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