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Re: [Bug-gsl] ode solve: adaptive step size control

From: Brian Gough
Subject: Re: [Bug-gsl] ode solve: adaptive step size control
Date: Tue, 09 Oct 2007 20:35:45 +0100
User-agent: Wanderlust/2.14.0 (Africa) Emacs/22.1 Mule/5.0 (SAKAKI)

At Mon, 8 Oct 2007 22:38:19 -0700,
Philip Du Toit wrote:
> I use gsl_odeiv_control to implement adaptive step size control.
> I understand that this function reduces the step size by a scaling  
> factor to ensure that an error tolerance is met.
> Is there any checking to be sure that underflow after many rescalings  
> does not cause the stepsize to become zero?


There isn't any checking for this, but it in practice it hasn't been
reported as a problem.  If you have an example program that shows it,
please could you send it as a bug report. Thanks.

> Is there anyway to ensure that the adaptive control never reduces the  
> stepsize below a prescribed lower bound regardless of the error?

It should be possible for you to check the value of h returned by
gsl_odeiv_evolve_apply -- it is only a suggested value so it is
possible to override it on subsequent calls.

best regards,

Brian Gough
(GSL Maintainer)

Network Theory Ltd,
Publishing the GSL Manual - http://www.network-theory.co.uk/gsl/manual/

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