From: Brian Gough <bjg@network-theory.co.uk>
To: Tuomo Keskitalo <Tuomo.Keskitalo@iki.fi>
Cc: gsl-discuss@sourceware.org
Subject: Re: GSL ode-initval development
Date: Wed, 03 Sep 2008 10:58:00 -0000 [thread overview]
Message-ID: <m3fxohwla9.wl%bjg@network-theory.co.uk> (raw)
In-Reply-To: <48BA4766.6070701@iki.fi> <48BD8EF0.5030502@iki.fi>
At Sun, 31 Aug 2008 10:25:26 +0300,
Tuomo Keskitalo wrote:
> I have been writing a non-linear equation solver based on a modified
> Newton iteration method, and a question about failures has come up. What
> value should the non-linear equation solver return to the stepper (and
> from there to user) in the case that the method reaches a maximum number
> of Newton iterations and therefore fails? GSL_CONTINUE or GSL_FAILURE or
> something else?
I'd suggest GSL_FAILURE to start with. Hopefully the solver won't fail
that often.
> which values of variables y should a stepper which uses step doubling
> for error estimation return: The values from the single step or the
> values from two half steps? You would expect to get the values of single
> step from "a stepper", but the values from two half steps should be more
> accurate, and they are available.
The final value of y should come from the two half steps as they are
more accurate. See rk4.c for an example and the error estimate.
--
Brian Gough
prev parent reply other threads:[~2008-09-03 10:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-17 8:39 Tuomo Keskitalo
2008-08-18 18:11 ` Brian Gough
2008-08-31 7:26 ` Tuomo Keskitalo
2008-09-02 19:08 ` ode-initval stepper logic Tuomo Keskitalo
2008-09-03 10:58 ` Brian Gough [this message]
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