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MathGroup Archive 2007

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Re: NDSolve doesn't stop

  • To: mathgroup at smc.vnet.net
  • Subject: [mg74358] Re: NDSolve doesn't stop
  • From: bar at ANTYSPAM.ap.krakow.pl
  • Date: Mon, 19 Mar 2007 05:52:43 -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:
> > notebook file is "not readable" so I put it on www
> > http://robox.ap.krakow.pl/~bar/pde.nb
> tmax = 20 ==> no warning message issued (indeed for any 0 < tmax <)
> 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 
> options. More...

 There is a problem, I can't see this message,
message window i empty, noetebook i running continuously,
without any message too,

(Mathematica 5.1
Linux localhost 2.6.19-gentoo-r5 #10 SMP PREEMPT Tue Feb 20 21:34:30 CET 2007 i686 Intel(R)
Pentium(R) 4 CPU 3.00GHz GenuineIntel GNU/Linux)

top shows 0%CPU, 0%Memory

When i try MaxStepSize->0.001
thet top shows 99%CPU
and %MEM is growing up to 100% (in about 5 minutes)
and %CPU decreases to 0%

In this time I killed process ...


There is a problem with my individual installation ?

The system of equations is not difficult, without nonlinearity,
I can solve it "hand-made" , by reduction to ODE equation
by separation t/x variable

I decided to use Math because i hoped to see solution
in addition nonlinearity ...

Regards , Olaf




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