Monday, January 15, 2007

Release 3.0l (download)

This release raises the instruction buffer size and documents the related performance issue. Problems related to setting -W (input window size) especially small or especially large were fixed: the new minimum is 16KB, the new maximum is 16MB. A regression in the unit test was fixed: the compression-level changes in 3.0k had broken several hard-coded test values.

The encoder has compression-level settings to optimize variously for time and space, such as the width of the checksum function, the number of duplicates to check, and what length is considered good enough. There are 10 parameters (Zlib, by comparision, has 4), but the flag which sets them (-C) is undocumented. I am documenting these and developing experiments to find better defaults.

There's a new page about external compression.

Thanks for your feedback (file a new issue).

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