Re: Re: odd behavior of NDSolve
- To: mathgroup@smc.vnet.net
- Subject: [mg11725] Re: [mg11702] Re: odd behavior of NDSolve
- From: David Withoff <withoff@wolfram.com>
- Date: Thu, 26 Mar 1998 03:08:53 -0500
> Richard Finley wrote: > > > Hi Selwyn, > > > > Actually, I don't believe there is any mystery behind the behavior. > > Since it is a numerical integration routine, it is subject to > > accumulated error depending on step size, maximum number of steps, > > etc...and it just so happens in this case that it becomes unstable > > around 12.03. > > Accumulated error is something I'm quite familiar with, but this > behavior is not about accumulated error. NDSolve is taking ONE giant > step, right past the interesting part of the solution when tmax > > 12.03. As Paul Abbott correctly pointed out, the real cause is the > default value of Infinity for MaxStepSize. (Seems to me that a more > sensible default for MaxStepSize might be something like tmax/10.) > > Selwyn If you want the maximum step size to be tmax/10, you could use MaxRelativeStepSize -> 1/10 so that the maximum step size will be limited to tmax/10 for any value of tmax. If you wish you could set this to be the default value of MaxRelativeStepSize. Dave Withoff Wolfram Research