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New post ompression rate in nanoseconds per byte on the largest file tested (e.g. seconds for enwik9). Speed is approximate and has no effect on ranking. A ~ means "very approximate". Not all tests are done on the same computer. Tests on my computer (Compaq Presario 5440, 2.188 Ghz Athlon-64 3500+, 2 GB memory, Windows XP SP2 or occasionally Ubuntu linux 2.6), are usually process times (user + system) measured with timer 3.01 by Igor Pavlov. This does not include disk I/O time, which can be significant for fast compressors. CPU time may increase because of Cool'n'Quiet, which updates the clock speed every 1/30 second and drops to 994 MHz if waiting on disk. I don't average over multiple runs. An underlined time means that no bet

ximate memory used for compression in MB. Decompression uses the same or possibly less. There is some ambiguity whether a megabyte means 10⁶ bytes or 2²⁰ bytes. The approximation is course enough that it doesn't matter. I use peak memory as measured with Windows Task Manager during compression (so if you really want to know, 1 MB = 1,024,000 bytes :) Memory does not include swap or temporary files. An underlined value means that no better compressor uses less memory.