[RC5] Runtime optimization??

Jim C. Nasby decibel at distributed.net
Wed Mar 1 19:39:12 EST 2006


On Wed, Mar 01, 2006 at 08:42:10PM -0300, D?cio Luiz Gazzoni Filho wrote:
> 
> On Mar 1, 2006, at 8:20 PM, Fugu wrote:
> 
> >Why don't the cruncher cores compiled using fftw-like optimizations?
> >Assembly code may be slightly faster, but in needs to be remade for  
> >every platform...
> 
> This technique is worthwhile in FFTW (and even then, specialized  
> packages handily beat FFTW) because of issues like memory/cache  
> organization, size, speed, etc. RC5 is immune to those variations --  
> it is only affected by register allocation and instruction scheduling.
> 
> An effective FFTW-like optimizer for RC5 would be pretty similar to a  
> general C compiler's code generator/optimizer. Not only is this an  
> overly complicated piece of software, but it can't schedule  
> instructions all that well anyway -- just look at the performance of  
> C cores. Plus I dare any compiler's code generator to produce  
> something like kakace's software pipelined Altivec+integer RC5 core.
> 
> By the way, `assembly code may be slightly faster' qualifies for  
> understatement of the year. Even generic assembly code, without  
> targeting a specific processor, would easily beat the C cores.

BTW, should you wish to prove Decio wrong or try your hand at this, the
source code for the clients is available for download. :)
-- 
Jim C. Nasby, Database Architect            decibel at distributed.net
Give your computer some brain candy! www.distributed.net Team #1828

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