Wednesday, December 8, 2010

LZ4 : New version

Following yesterday's improvements on MMC search algorithm, here comes logically a new version of LZ4 "HC", for High Compression, which serves as a living demo to MMC.

It's noticeably faster, about 20% more than earlier "Fusion" version, which makes it close to 40MB/s. Not too bad considering it is a full search. The new version 0.8 can be downloaded on LZ4 Homepage.

While working on the multi-level promotion improvement, i made a small mistake in the length counter loop, which made me discover a new trick about buffer management. Thanks to this trick, less verifications are necessary, and therefore speed is a little bit increased. This trick can be re-used in many other context, and as a consequence, can be speed up LZ4 Ultra-Fast too, which make it even faster. So you'll find a new version of LZ4 too. Funny how new ideas are sometimes discovered ...

versionCompression RatioSpeedDecoding
LZ4 "Ultra Fast"0.52.062232 MB/s780 MB/s
LZ4HC "High Compression"0.82.34538.2 MB/s835 MB/s

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