Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!spool.mu.edu!mips!atha!aunro!alberta!edson!news
From: jpenne@ee.ualberta.ca (Jerry Penner)
Newsgroups: comp.dsp
Subject: Re: Fast way to evaluate an exponential
Message-ID: <1991Jun9.082640.26871@ee.ualberta.ca>
Date: 9 Jun 91 08:26:40 GMT
Article-I.D.: ee.1991Jun9.082640.26871
References: <1991Jun9.071214.2073@noose.ecn.purdue.edu>
Sender: news@ee.ualberta.ca
Organization: University of Alberta Electrical Engineering
Lines: 13

In article <1991Jun9.071214.2073@noose.ecn.purdue.edu> muttiah@stable.ecn.purdue.edu (Ranjan S Muttiah) writes:
>
>Is there a fast way to evaluate e^-x (using table look ups) than having to
>use exp(.) in c ?  I have to call the exponential many times and looking for
>ways to save time.

Yes, use CORDIC algorithms.  These beasties usually use fixed point
arithmetic.  A recent issue of Dr. Dobbs Journal (hopefully available
at your library) gives a description and source code.  They don't use
table lookups but are fast.
-- 
Jerry Penner		  | jpenne@bode.ee.ualberta.ca
Edmonton, Alberta, Canada |  OR  alberta!bode!jpenne