fast arc tangent routine available?

[mcdonald at uxe.cso.uiuc.edu]

>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