Fwd: [openZIM dev-l] LZMA is working now

Mirko Lindner mirko at sharism.cc
Fri Jan 1 11:09:57 EST 2010


Hey,

here a mail Tommi (the main developer of the ZIM project) sent to the ZIM
developer-list yesterday, which is very encouraging for vido and openzim on
the NanoNote.

Happy new year everyone :)

/mirko

---------- Forwarded message ----------
From: Tommi Mäkitalo
Date: Thu, Dec 31, 2009 at 4:03 PM
Subject: [openZIM dev-l] LZMA is working now
To: dev-l at openzim.org


Hi,

I talked with the xz developer in IRC and he helped me to reduce memory
usage.

The problem was, that compressing with lzma with 9 uncompressing needs about
65MB of RAM. The needed memory is in fact dependend of used compression
level.
Using level 3 reduced the memory usage to about 1,5MB, that it works now on
the NanoNote. There is a additional flag LZMA_PRESET_EXTREME, which makes
compressing slower but compression ratio better. Using 3 + extreme results
in
a file, which works on Nanonote while the size is almost identical with 9 or
bzip2.

Uncompressing bzip2 chunks take about 2 seconds while lzma needs 0,5 seconds
on the nanonote. So we keep the size while improving speed with the factor
4!!!

Have a good Year.

Tommi
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