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 ==== [MESSAGE SEPARATOR] ====