FindRoot problem
- To: mathgroup at smc.vnet.net
- Subject: [mg4812] FindRoot problem
- From: "Arturas Acus" <acus at itpa.lt>
- Date: Fri, 20 Sep 1996 01:12:37 -0400
- Sender: owner-wri-mathgroup at wolfram.com
Dear All,
I came to the conclusion that FindRoot sometimes behaves a bit
strange. Say I want to calculate:
x=x/.First[FindRoot[(x-Pi),{x,-4,4},AccuracyGoal->20, WorkingPrecision->30,
Compiled->False,MaxIterations->Infinity]
The result of this is MachineNumber!!! It seems, problem is related
with evaluation of Pi. And hint N[Pi,30] do not help!!
Then I tried:
x=x/.First[FindRoot[x-Rationalize[N[Pi,30],0],{x,{-4,4}},
Compiled->False,AccuracyGoal->20,MaxIterations->Infinity,
WorkingPrecision->30]]
3.141592653589793238462643383279
Now it works correct. Does anybody had similar problem?
I tried two methods: secant and brent's. Both gives the same
results. Can anybody explain this behaviour? This is important for my
job.
Sincerely
Arturas Acus
Arturas Acus
Institute of Theoretical
Physics and Astronomy
Gostauto 12, 2600,Vilnius
Lithuania
E-mail: acus at itpa.lt
Fax: 370-2-225361
Tel: 370-2-612906
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