MathGroup Archive 2006

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: NDSolve::ndsz question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg63696] Re: NDSolve::ndsz question
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 10 Jan 2006 01:48:51 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <dpnqoa$6rh$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

you may use high-precision computation (avoid 0.5 and 0.1 and use
1/2 and 1/10 instead) if you know that your solution has no
singularity -- otherwise you must program an initial value solver
that use rational approximations to the function instead of polynomes.

Regards
  Jens

"Flip" <fliptomato at gmail.com> schrieb im 
Newsbeitrag news:dpnqoa$6rh$1 at smc.vnet.net...
| Greetings, I'm trying to solve a differential 
equation  but I'm getting
| the following error:
|
| NDSolve::ndsz: At x == 18.84025621252942`, step 
size is effectively
| zero; \
| singularity or stiff system suspected
|
| I'm not sure how to deal with this--is there a 
way to allow smaller
| step sizes? Here is my complete code:
|
| k := 400000000;
| b  := 0.0023;
| epsR := 0.024;
| solution := NDSolve[
| {y'[x] == -k x^(-0.5) \[ExponentialE]^(-epsR x) 
(y[x]^2 - (b x^2
| BesselK[2,x])^2),
| y[0.1] == b*BesselK[2,0.1]/(0.1)}, y, 
{x,0.1,5000}]
| Evaluate[y[5000] /. solution]
|
| Any thoughts would be appreciated! Thanks,
| Flip
| 



  • Prev by Date: Re: Getting the value of the independent var from the dep.var using NDSolve
  • Next by Date: Re: Re: Can anybody help?
  • Previous by thread: Re: NDSolve::ndsz question
  • Next by thread: Re: NDSolve::ndsz question