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MathGroup Archive 2007

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Re: NDSolve doesn't stop

  • To: mathgroup at smc.vnet.net
  • Subject: [mg74360] Re: NDSolve doesn't stop
  • From: bar at ANTYSPAM.ap.krakow.pl
  • Date: Mon, 19 Mar 2007 05:53:49 -0500 (EST)
  • Organization: Akademia Pedagogiczna w Krakowie
  • References: <etikd4$j5c$1@smc.vnet.net> <etlchi$nrv$1@smc.vnet.net>

Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com> wrote:

> {{ET -> InterpolatingFunction[{{0., 20.}, {0., 1.}}, <>], FI -> \
> InterpolatingFunction[{{0., 20.}, {0., 1.}}, <>]}}
> tmax = 21 ==> a warning message is issued: it might be worth reading it
>   NDSolve::"eerr" : "Warning: Scaled local spatial error estimate of 
> (159.0346060966196) at (t) = (21.) in the direction of independent 
> variable (x) is much greater than prescribed error tolerance. Grid 
> spacing with (15) points may be too large to achieve the desired 
> accuracy or precision. A singularity may have formed or you may want to 
> specify a smaller grid spacing using the MaxStepSize or MinPoints 

Success!, Bun i'm not suse how it works :-)
When i put:
PrecisionGoal ->10 (if need by)
MaxStepSize->0.005
MaxSteps->Infinity

I can obtain silution for a long time (t=100 is enough)
My question is : Is there optimal procedure to change this parameters?

Pegards, Olaf



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