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From: | Jonny Taylor |
Subject: | Re: [Help-gsl] ODE solvers and overdamped motion |
Date: | Fri, 11 Sep 2009 12:04:55 +0100 |
(1) is an improvement, but a monotonic decrease in abs(y) would have been nice. (2) is a big disappointment because my highest priority is lower run-time. (3) causes quite a few problems because evaluating such configurations accurately is difficult to impossible, and I am wary about "lying" to the solver in my response without knowing what knock-on effect that might have.
Does this sound like what you would expect, or am I still misusing something?
Cheers Jonny On 11 Sep 2009, at 11:26, Frank Reininghaus wrote:
Hi, 2009/9/11 Jonny Taylor <address@hidden>:the issue I am having can be seen in a simple overdamped springcalculation (the derivatives function simply returns dydt[i] = -y [i] * 9.0).Such ODEs are called 'stiff equations', see http://en.wikipedia.org/wiki/Stiff_equationThis makes me wonderif there is something I can do, or a different stepper I can use, that will improve the performance. I wonder if fundamentally the problem is that themotion involved is exponential decayThis is indeed the case. You might want to try one of the implicit ODE solvers.Best regards, Frank
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