- To: mathgroup at smc.vnet.net
- Subject: [mg32040] Re: NDSolve-memory
- From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
- Date: Thu, 20 Dec 2001 03:42:02 -0500 (EST)
- Organization: Universitaet Leipzig
- References: <email@example.com>
- Sender: owner-wri-mathgroup at wolfram.com
my package with Runge-Kutta solvers
has a RKReturn option. With RKReturn->RKEndPoint no interpolation is
and only the end point is returned. If you set RKReturn->
interpolation function is generated.RKReturn->RKPoincareSection make a
Poincare section on the hypersurface that is given by PSHyperplane
The solvers expect a system of first order equations. The equations must
autonom. The Runge-Kutta methods are for non-stiff and middle-stiff
With the Method option you can select methods of order 3-8 and atleast
higher order metthods should work with middle stiff problems.
The RKReturn->RKEndPoint option should solve your problem.
Pieter-Jan.DeSmet at fys.kuleuven.ac.be wrote:
> Dear readers,
> I have a system of differential equations
> F( y(t) ,y'(t) ,t )=0, with initial condition y(0) = y0.
> Here y(t) is a vector-valued function, let us denote the dimension of
> this vector by n. When I solve this system in Mathematica with NDSolve,
> the program uses too much memory and crashes if n is too big.
> (In my case this happens when n = 6).
> I am however only interested in the value of y at t=1 ( y(1) ). So, I think
> that Mathematica can be more memory efficient if it throws away all
> previous values of y(t) it does not need anymore in its difference scheme. Is
> there a method to impose this? Of course, the result of NDSolve would not give
> an InterpolatingFunction object any more.
> Other suggestions to reduce the needed memory are also appreciated. Lowering
> PrecisionGoal and AccuracyGoal does not seem have much effect on the memory.
> Pieter-Jan De Smet
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