Re: How to cope with tiny numbers in FindRoot
- To: mathgroup at smc.vnet.net
- Subject: [mg63204] Re: How to cope with tiny numbers in FindRoot
- From: "Jean-Marc Gulliet" <jeanmarc.gulliet at gmail.com>
- Date: Mon, 19 Dec 2005 07:00:57 -0500 (EST)
- Organization: Open University, U.K.
- References: <dnrn37$pvo$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
<dkjk at bigpond.net.au> a écrit dans le message de news: dnrn37$pvo$1 at smc.vnet.net... | Hi group, | | I'm trying to numerically determine the solution of an equation whose | coefficients are of the order 10^-100 or less. I've been running into | all sorts of errors relating to MaxIterations and step size but so far | I haven't been able to find any useful information in the Mathematica | book. If you're interested in the notebook i'm using, you can find it | here: | | http://users.bigpond.net.au/jdstokes/theory2.nb | | Thanks | | James. | Hi James, Having read more carefully your mail and notebook, I may suggest some options that should help *FindRoot* to deal with small coefficients: 1 - Try not to use the package _RealsOnly_ so Mathematica is free to use the full range of its internal algorithms (even those that might involve at some stage use the complex plane). 2 - Enter all the numeric values as exact numbers, 1/2 or 606992/10^5 rather than 0.5 or 6.06992 for instance. 3 - Use the optional parameters *WorkingPrecision* and *MaxIteration* with sufficiently high values: I have done some test with 1000 and 500 respectively and got solutions for {omega-ro, 1, 10, 10} and {omega-z, 1, 30, 10}. Best regards, /J.M. 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