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Date: Wed, 22 Dec 2004 16:56:24 +0100
From: =?iso-8859-1?Q?J=F6rn?= Engel <joern@wohnheim.fh-wedel.de>
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Subject: Re: JFFS3 & performance
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On Wed, 22 December 2004 16:30:20 +0100, Joakim Tjernlund wrote:
> 
> Can you do
> 1) First run a forward and then a backward version on memory space >= 2*L1 cache
> 2) Then do two forward runs on the same memory.
> 
> Compare the delta between 1) and 2)
> That should give a clue if it is worth having a backward version.

In my private not-too-scientific hash-table test, I do a strlen()
before calling engel32.  The reverse version is 1.5% faster, even
though the strings are in the 80byte arena.  That's well over noise
level.

> > Adler32 beats the hell out of every other algorithm.  Except for the
> > backwards part, it appears to be a clear winner.
> 
> Have you look at the assembler Engler32 generates? Every instruction counts
> in such small loops.

Not yet.  Might be worth a try, though.  Since it's losing in direct
comparison, but equal in the hash test, it might be slightly stronger
than adler32.

BTW: I reject the name "Engler32".  Few names are worse than
"engel32", but that one is. ;)

Jörn

-- 
A defeated army first battles and then seeks victory.
-- Sun Tzu