README

About libfreevec 

libfreevec is a free (LGPL) library with hand-optimized replacement routines 
for GLIBC, such as memcpy(), strlen(), etc. These routines have been written 
specifically to take advantage of the AltiVec (a.k.a Velocity Engine or VMX), 
and will only work on processors that include this unit. This means they will 
not work on older processors, such as 603, 604, 750 (G3) or the POWER family 
of CPUs. 

Check the Features (http://www.freevec.org/features.php) page for more details
on the exact set of functions that are included, with comments and rough 
speed gain estimates, and the FAQ for additional information about using 
the library itself. 


The author writes on the history of libfreevec: 


"I have been a PowerPC user for many years, but I had never had the opportunity 
to work with a G4 processor until late September 2004. At that time, I attended 
various AltiVec tutorials/seminars at the Euro SNDF show which were held by Dr 
Sergei Larkin and Chuck Corley from Freescale. I would like to thank both of 
them as they provided myself with the inspiration to work on the AltiVec engine. 
During said seminars, I was shown how much performance is hidden in this small 
and underestimated CPU. In times when everyone seems to be focused on 64-bit 
technology, it is no surprise that some people dismiss the G4 processor as 
outdated technology. If only you knew... 

Thanks to the support by Genesi and Freescale, I was given an Open Desktop 
Workstation for development purposes at the show and was highly motivated 
to do software development on this platform. Soon after the seminars ended, 
I started researching for source code on programming the AltiVec unit and 
its applications. To my surprise, I discovered that the G4 vector engine 
is basically unused by Linux itself which happens to be my platform of choice 
whereas it speeds up many system components in MacOS X. 

Why is this so? I have not found a definite answer to this question. One 
possible reason could be that AltiVec was originally designed as a multimedia 
extension and for processing media data. While this simple fact cannot be 
denied, it is still no convincing argument why this exciting technology has 
been neglected and not been used for more ordinary tasks which might increase 
the performance of the whole system. 

For example, did you know that you can do byte swapping with AltiVec 7 times 
faster than with scalar code? Or that it is possible to sort integers and 
floats 4 times faster with the help of AltiVec? Were you aware that it helps 
to do string searching faster? Memory hashing gets upto 7 times faster. The 
list could just go on and on... 

With these things in mind, I was determined to take an active role in allowing 
Linux and other operating systems to profit from AltiVec on a system wide 
scale. With the financial help of Genesi, I was able to start work on 
libfreevec which is presented to you on this website. libfreevec is a library 
with many common glibc routines, rewritten and optimized to use the vector 
engine found in the G4/G4+ PowerPC CPUs by Freescale. These processors are 
most commonly used in Apple Mac computers and the Genesi Pegasos II Open 
Desktop Workstation (ODW). In addition to the glibc routines, it also 
includes custom routines which were designed to speed up various other 
performance-critical tasks. For example, it includes special AltiVec 
optimized versions of various string and memory functions from libstring 
which is part of the MySQL package. 

Eventually, I hope to see the code being integrated in glibc so that the 
whole Linux system may benefit from AltiVec when run on the right hardware. 
The current version is released under the terms of the free LGPL license and 
I sincerly hope that it will enable many interested developers to give a 
performance boost to their applications for the PowerPC platform."