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MathGroup Archive 2003

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Re: serious NDSolve bug?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg44026] Re: serious NDSolve bug?
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sat, 18 Oct 2003 03:12:17 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <bmod0f$hof$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de
  • Sender: owner-wri-mathgroup at wolfram.com

Hi, 

and whe you write

f[kampas_?NumericQ]:=(u[\[Xi]] /. First[sprendinys1 =
 NDSolve[{Derivative[2][\[Psi]][\[Xi]] == (\[Xi]^2 - energija)*
            \[Psi][\[Xi]], Derivative[1][u][\[Xi]] == \[Psi][\[Xi]]^2,
 \[Psi][\[Xi]min] == 0,
           Derivative[1][\[Psi]][\[Xi]min] == kampas, u[\[Xi]min] == 0},
 {\[Psi][\[Xi]], u[\[Xi]]},
          {\[Xi], \[Xi]min, \[Xi]max}]] /. \[Xi] -> \[Xi]max)

and call

 teisingasKampas =
    FindRoot[f[kampas]==1, {kampas, -0.04, 0.04}]

all works as expected *and* your code is better readable.

BTW: Can you avoid postings with Mathematica's special characters ?

Regards
  Jens

Artþras Acus wrote:
> 
> Hi, All
> 
> In version 4.1 the following code works as expected.
> 
> \[Xi]min = -5; energija = 2*n + 1 /. n -> 1; \[Xi]max = 5;
> 
> teisingasKampas =
>   FindRoot[
>    (u[\[Xi]] /. First[sprendinys1 =
> NDSolve[{Derivative[2][\[Psi]][\[Xi]] == (\[Xi]^2 - energija)*
>             \[Psi][\[Xi]], Derivative[1][u][\[Xi]] == \[Psi][\[Xi]]^2,
> \[Psi][\[Xi]min] == 0,
>           Derivative[1][\[Psi]][\[Xi]min] == kampas, u[\[Xi]min] == 0},
> {\[Psi][\[Xi]], u[\[Xi]]},
>          {\[Xi], \[Xi]min, \[Xi]max}]] /. \[Xi] -> \[Xi]max) == 1,
> {kampas, -0.04, 0.04}]
> 
> In 5.0 I get message, that kampas is not a number. Changing FindRoot[ ]
> by RootSearch[] (from Ted Ersek package) did not help, therefore I
> suspect that there is serious bug in NDSolve argument evaluation
> procedure. How I can make it to work ?
> 
> Sincerely, Arturas Acus


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