[Libreoffice] Windows installer size reduction effort - the compression theory

Kálmán „KAMI” Szalai kami911 at gmail.com
Tue Mar 1 05:39:39 PST 2011

Hi Michael,

2011-02-28 13:16 keltezéssel, Michael Meeks írta:
> Hi Kami,
> 	Wow - I'm so sorry, I missed your sexy mail for a week; that sucks -
> over-much merging on another branch :-) Tor has been on FTO, and
> Fridrich with his head down releasing 3.3.1 (and the Novell LibreOffice
> product) - which in part explains the lack of response to you (and
> Steven) - which sucks - sorry guys.
> On Tue, 2011-02-22 at 17:32 +0100, Kálmán „KAMI” Szalai wrote:
>> I ran few test to figure out what is the best method for installset
> 	These look great, nice spreadsheet.
Thanks, I just wanted to follow your helpful spreeadsheet :o).
>> So I went to other direction, whatif I increase the efficiency of LZM
>> compression of makecab. I found that we can use .Set CompressionMemory=
>> 21 setting. This setting produces 83,91% of original installer size and
> 	Oh - nice :-) that solves the install-space problem as well.
>> In the gray section I tried a special way when I uncompressed every
>> zip container (ODF, JAR, ZIP, etc) in the installset and every file
>> contains only stored data without compression. In this way I was able
>> to gain more 15 MB, but this require zip recompressing at the end of
>> installation process that may make it to complex and time consuming.
>> Please check the attached document, and if you want to go with it
>> apply the attached patches.
> 	Oh ! that sounds fun :-) 15Mb for that. Actually on master - we could
> use flat ODF files and get the same result (for some on-disk size
> growth) without having to re-compress, and they're dead fast in master.
> 	So - personally, I find it amazing that ZIP is better than LZMA - ever,
> it is such an older compression algorithm, and this flies in the face of
> everything I've seen in practise with it [ eg. we use LZMA for our RPMs
> in openSUSE these days AFAIR, better than bzip2, which in turn was
> better than .tgz (essentially zip) ].
I think the story is a bit different. Recompressing the already
compressed data is a simply waste of time and horsepower. It is always
better to compress uncompressed data. If you comapre zip and LZMA on the
whole uncompressed installer I am sure LZMA will provide much better
compression ratio.
> 	It'd be great to commit the first patch but can we instead hack:
> 	solenv/bin/modules/installer/globals.pm to patch:
>     $cabfilecompressionlevel = 7;
> 	rather than hard-coding that and leaving the variable there.
> 	The second - can you really confirm that LZMA is worse than zip ?
As I described below, I think as always recompressing compressed files
may have penalty in term of compression ration.
> 	Anyhow - great work :-)
I will provide a patch for it, thanks.
> 		Michael.

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