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From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.lang.c
Subject: Re: fast arc tangent routine available?
Message-ID: <225800217@uxe.cso.uiuc.edu>
Date: 31 Aug 89 16:22:00 GMT
References: <6002@pt.cs.cmu.edu>
Lines: 12
Nf-ID: #R:pt.cs.cmu.edu:6002:uxe.cso.uiuc.edu:225800217:000:446
Nf-From: uxe.cso.uiuc.edu!mcdonald    Aug 31 11:22:00 1989


>Hello, does anyone know if there are any 'arc tangent' routines, which run
>faster than atan() and atan2() of the standard C math library?

Range reduce the problem down to 0 to pi/4 (from pi/4 to pi/2 there
is an obvious geometrical relation to 0 to pi/4).

Then use a table lookup with both starting points and slopes stored
at a suitable number of points. For high accuracy you might need to
store quadratic coefficients also.

Doug McDonald