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Re: [Axiom-developer] Approximating Ei using polynomials

From: M. Edward (Ed) Borasky
Subject: Re: [Axiom-developer] Approximating Ei using polynomials
Date: Thu, 17 Jan 2008 19:32:11 -0800
User-agent: Thunderbird (X11/20071227)

address@hidden wrote:
> The A&S handbook lists polynomial coefficients for approximation of E1,
> the exponential integral. Does anyone know how these coefficients were
> derived? Is it a chebyshev polynomial? I want to dynamically compute
> these coefficients to the required precision.
> Tim
> _______________________________________________
> Axiom-developer mailing list
> address@hidden

Aren't there references in A&S? I don't have my copy handy, but IIRC
everything in there was painstakingly documented. In the good old days
of expensive scientific computing, finding things that could be computed
accurately with as few multiplies and divides as possible was a very big
deal. Extra points were awarded for methods that got decent results
using the crappy floating point arithmetic most machines had prior to
IEEE 754. :)

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