[GRASSLIST:6153] Re: Altivec optimization for GRASS modules?

[Lorenzo Moretti]

Hi
>  > Just curious.... has anyone thought about adding the possibility for
>>  Altivec acceleration to the source for any of the GRASS modules?
>
>
>for anyone (like me) who has no idea what Altivec is:
>
>   http://en.wikipedia.org/wiki/Altivec
>
>
>
>Hamish

It's a flag question from compiler (gcc 3.3) but remember, for 
example, now Grass use FFTW 2.1.5 library and it's not compatible 
with 3.0 lib that has Altivec inside.
Now blas and lapack libs are substituted with flag -framework vecLib 
http://developer.apple.com/releasenotes/MacOSX/vecLib.html

In the future will be possible to optimize Grass for 64 bit G5 
processor. From user reviews on OS X the performances are very good 
now with the normal flags. These compiler flags are more compatible 
for all OS X versions (10.2, 10.3, 10.4) and all processors (G3, G4 
altivec, G5 64 bit)


There are info about Altivec with a new good version of gcc 4.0 but 
only for 10.3 at http://hpc.sf.net

 From site
GCC 4.0 (auto-vectorizing) :

Recently compiled using source code from the GNU CVS servers, 
autovect-branch .  This contains beta versions of gfortran (GNU F95) 
and gcc (GNU C) compilers that can  perform limited 
auto-vectorization (i.e. modify code to take advantage of AltiVec, 
automatically).  Use flags -ftree-vectorize -maltivec to enable that 
option. For more information,  see this webpage .  Download my 
binaries, and cd to the download folder. Then gunzip 
gcc-vec-bin.tar.gz (if your browser didn't do so already) and sudo 
tar -xvf gcc-vec-bin.tar -C / .  It installs everything in /usr/local 
.  You invoke g95 by typing gfortran . Note that you may need to add 
the flag -lstdc++ for getting it recognize some of the unimplemented 
standard functions.  You will also need to have Apple's Developer 
Tools installed. They are included on a  separate CD in the retail 
version of OS X and also available as a free download from Apple's 
Developer Site .  Please install the most current version of 
Developer Tools.



Bye

-- 
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