Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!amdahl!nsc!taux01!yuval
From: yuval@taux01.UUCP (Gideon Yuval)
Newsgroups: comp.arch
Subject: Re: Performance increase - a suggestion
Message-ID: <481@taux01.UUCP>
Date: 5 Feb 88 07:35:01 GMT
References: <3127@phri.UUCP> <9408@steinmetz.steinmetz.UUCP>
Reply-To: yuval@taux01.UUCP (Gideon Yuval)
Organization: National Semiconductor (Israel) Ltd.
Lines: 11
Summary: Newton-Raphson is NBG if IEEE standard FP needed

In a recent message, Dennis O'conner says:
>Message-ID: <9408@steinmetz.steinmetz.UUCP>

> NO. Sorry. But the fastest floating point division and root
> algorithms use Newton-Rapheson iteration, where the time to
> solution is proportional to log2( number_of_bits_of_result ).

Since, under machine arithmetic, a/b is NOT equal to a*(1/b), and since the
IEEE floating-point standard demands EXACT rounding, I don't see how Newton-
Raphson is any use an an IEEE environment.
-- 
Gideon Yuval, +972-52-522255 (work), -2-690992 (home), yuval@taux01.nsc.com