RE: Linux Kernel Floating Point Emulation and CORDIC

nathan.zook@amd.com
Fri, 24 Dec 1999 16:53:56 -0600

EEEEEwwww! Cordic is UGLY! There is a reason that Intel & we (AMD) have
gone with polyonmial & rational function approximations. BTW, our
algorithms are quite accurate. If you are running in another world, or just
want to emulate, look into equal-ripple approximations. You will chew some
serious processor power finding good functions, but what you get can be
nice.

Nathan

> -----Original Message-----
> From: Arthur Jerijian [SMTP:lightmanaj@earthlink.net]
> Sent: Thursday, December 23, 1999 5:58 PM
> To: linux-kernel@vger.rutgers.edu
> Subject: Linux Kernel Floating Point Emulation and CORDIC
>
> For the mathematics and theoretical computer science enthusiasts here on
> this
> list:
>
> I have taken a look at the source code of the Linux Kernel floating point
> emulation engine for i386 (as of 2.2.12, don't know if it changed in
> 2.3.x). I
> noticed that it uses Taylor/Maclaurin polynomials to approximate the sine,
> cosine, tangent, and inverse tangent functions. Wouldn't CORDIC be a
> better
> algorithm for computing trigonometric and exponential functions instead?
> CORDIC
> is a method for calculating mathematical functions using only addition,
> shifting, and looking up entries in a table. More details can be found at
> http://www.ezcomm.com/%7Ecyliax/Articles/RobNav/sidebar.html
>
> Thanks,
> --Arthur
>
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