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Message-ID: <472A8686.4080500@zytor.com>
Date: Thu, 01 Nov 2007 19:08:06 -0700
From: "H. Peter Anvin" <hpa AT zytor DOT com>
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CC: Robert Riebisch <Robert DOT Riebisch AT arcor DOT de>
Subject: Re: Why "upx --brute" might be a bad idea...
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H. Peter Anvin wrote:
> Robert Riebisch wrote:
>> Hi!
>>
>> Please read this thread at
>> <http://www.bttr-software.de/forum/forum_entry.php?id=1220>, how UPXed
>> binaries cause compile slowdowns.
>>
> 
> "upx --brute" and "upx --ultra-brute" runs a bunch of algorithms, and 
> picks the smallest one, which may or may not be LZMA.  I don't know how 
> they affect decompression speed, and it would be interesting to find out.
> 
> In particular, the NASM build robot 
> (ftp://ftp.zytor.com/pub/nasm/snapshots/) appear to generate marginally 
> smaller binaries with --[ultra-]brute than with --lzma --best, and I'm 
> wondering where the difference comes from.  It would also be nice to 
> know what algorithm it ends up using so I can tell it to use the same 
> one every time, instead of trying them all every time taking time (a 
> whopping minute every night ;)
> 

Just found upx --lzma --best --all-filters which generate the same 
output as --[ultra-]brute.

	-hpa