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Re: ndsolve

  • To: mathgroup at smc.vnet.net
  • Subject: [mg22450] Re: ndsolve
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sun, 5 Mar 2000 00:23:46 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <89ibli$mvi@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

a) the Programming in Mathematica packages has a fixed stepsize
Runge-Kutta 
   method of order 4

   <<ProgramingInMathematica`RungKutta`
 
   will load the solver.

b) never uses an initial value solver without a step sizs control !
   A constant stepsize solver is slower, make more steps and 
   accumulate rounding errors. 

Hope that helps
  Jens

Bernd Brandt wrote:
> 
> Dear members,
> 
> Does NDSolve have an option to use FIXED stepsize, e.g. in RungeKutta?
> 
> NDSolve[{y'[x] == y[x], y[0] == 1}, y, {x, 0, 1}, Method -> RungeKutta,
> StartingStepSize -> 1, MaxStepSize -> 1]
> 
> This obviously will not work since stepsize control still functions.
> How can i reduce the RungeKutta-Fehlberg to a simple RK4?
> 
> Thanks,
> Bernd


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