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Re: Numeric root-finding in Python

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From Robert Kern <robert.kern@gmail.com>
Subject Re: Numeric root-finding in Python
Date Sun, 12 Feb 2012 13:52:48 +0000
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On 2/12/12 6:41 AM, Steven D'Aprano wrote:
> This is only peripherally a Python problem, but in case anyone has any
> good ideas I'm going to ask it.
>
> I have a routine to calculate an approximation of Lambert's W function,
> and then apply a root-finding technique to improve the approximation.
> This mostly works well, but sometimes the root-finder gets stuck in a
> cycle.

I don't have any advice for fixing your code, per se, but I would just grab 
mpmath and use their lambertw function:

http://mpmath.googlecode.com/svn/trunk/doc/build/functions/powers.html#lambert-w-function

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco

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Thread

Numeric root-finding in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-12 06:41 +0000
  Re: Numeric root-finding in Python Eelco <hoogendoorn.eelco@gmail.com> - 2012-02-12 02:10 -0800
    Re: Numeric root-finding in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-02-12 13:39 +0000
    Re: Numeric root-finding in Python Terry Reedy <tjreedy@udel.edu> - 2012-02-12 16:19 -0500
  Re: Numeric root-finding in Python 88888 Dihedral <dihedral88888@googlemail.com> - 2012-02-12 05:13 -0800
  Re: Numeric root-finding in Python Robert Kern <robert.kern@gmail.com> - 2012-02-12 13:52 +0000
    Re: Numeric root-finding in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-12 22:53 +0000
  Re: Numeric root-finding in Python inq1ltd <inq1ltd@inqvista.com> - 2012-02-12 10:20 -0500
    Re: Numeric root-finding in Python David Monaghan <monaghand.david@gmail.com> - 2012-02-21 01:33 +0000
      Re: Numeric root-finding in Python Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-02-21 02:21 +0000
  Re: Numeric root-finding in Python Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-02-12 11:47 -0500
  Re: Numeric root-finding in Python Dave Angel <d@davea.name> - 2012-02-12 12:00 -0500
  Re: Numeric root-finding in Python Mark Dickinson <mdickinson@enthought.com> - 2012-02-12 12:18 -0800
    Re: Numeric root-finding in Python Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-12 23:05 +0000
      Re: Numeric root-finding in Python Dave Angel <d@davea.name> - 2012-02-12 18:52 -0500

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