Comments on: Fixed point math in pure CPP http://manuel.bit-fire.com/2007/10/31/fixed-point-math-in-pure-cpp/ Fri, 19 Mar 2010 20:31:25 +0000 hourly 1 http://wordpress.org/?v=3.0.1 By: Manuel http://manuel.bit-fire.com/2007/10/31/fixed-point-math-in-pure-cpp/comment-page-1/#comment-9655 Manuel Wed, 05 Dec 2007 23:21:00 +0000 http://manuel.bit-fire.com/?p=78#comment-9655 Thank you for your feedback Kurt: i performed various test at the time on a desktop machine, obviously with a release build, but on a Pentium D i didn’t notice improvements at all, floating point was showily faster than anything else. It may be possible that my tests weren’t exhaustive as they should, i used a matrix-based test and a 3d rasterizer: both tests showed up big fixed point improvements on mobile platforms but none on the desktop. I’ll try to search my old tests, too bad i don’t think i still have what i used at the time.. Have you played with compiling/linking options and stuff like that? Thank you for your feedback Kurt: i performed various test at the time on a desktop machine, obviously with a release build, but on a Pentium D i didn’t notice improvements at all, floating point was showily faster than anything else.
It may be possible that my tests weren’t exhaustive as they should, i used a matrix-based test and a 3d rasterizer: both tests showed up big fixed point improvements on mobile platforms but none on the desktop.
I’ll try to search my old tests, too bad i don’t think i still have what i used at the time..
Have you played with compiling/linking options and stuff like that?

]]> By: Kurt Guntheroth http://manuel.bit-fire.com/2007/10/31/fixed-point-math-in-pure-cpp/comment-page-1/#comment-9654 Kurt Guntheroth Mon, 03 Dec 2007 21:43:00 +0000 http://manuel.bit-fire.com/?p=78#comment-9654 I am the “Kurt” referenced in the article. My experience is that fixed-point costs about 15% more than integer math, and is about twice as fast as floating point math on Intel Pentium-4 processors, and using Microsoft visual c++ versions from 6 to .Net-2005. In evaluating the performance of fixed point arithmetic routines, it is important to compile a “release” build. On debug builds, the compiler creates function calls for all your template functions. Function call overhead eats the performance gains from using fixed point. I am the “Kurt” referenced in the article. My experience is that fixed-point costs about 15% more than integer math, and is about twice as fast as floating point math on Intel Pentium-4 processors, and using Microsoft visual c++ versions from 6 to .Net-2005.

In evaluating the performance of fixed point arithmetic routines, it is important to compile a “release” build. On debug builds, the compiler creates function calls for all your template functions. Function call overhead eats the performance gains from using fixed point.

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