Overall Results

Size

The results are shown as the percentage of the average size then averaged over all the tests.

7z	72.4%
ace	80.4%
arj	98.7%
jar	99.4%
lha	97.0%
rar	86.9%
sit	90.0%
tar.bz2	84.8%
tar.gz	96.3%
tar.lzo	106.9%
tar.Z	142.3%
zip	98.5%
zoo	146.3%

The clear winner seems to be 7z. Ace gets a good second but it is 10% larger than 7z. The next bunch are bz2, rar and sit. These stand above the rest which generally got similar results with the exceptions of compress and zoo. It is possible to split the compressors into generations. Zoo and compress (tar.Z) are the first generation and perform very poorly. Arj, jar, lha. gzip and zip are the everyday compressors which we grew up with in the second generation of compressors. Rar, bzip2 and sit are third generation which are taking over the current third generation. Ace seems to have got something right and they extend the third generation forward but not enough to break away. And 7z seems to be the start of the forth generation. The format and the source are open so I wouldn't be surprised to see a range of tools adapting it and filling the fourth generation.

Compression time

7z	265.2%
arj	41.0%
jar	43.2%
lha	123.6%
rar	168.8%
sit	172.7%
tar.bz2	110.1%
tar.gz	74.8%
tar.lzo	168.7%
tar.Z	37.8%
zip	65.4%
zoo	28.7%

7z performs the slowest on the compression time but this can be excused due to its compression ratio. Zoo and compress are fastest performers but they have poor compression. Arj and jar, which got similar sizes to zip and lha, but perform faster than others in their group.

Decompression time

7z	99.3%
ace	90.2%
arj	49.0%
jar	15.3%
lha	35.0%
rar	147.1%
sit	505.3%
tar.bz2	233.1%
tar.gz	16.6%
tar.lzo	3.4%
tar.Z	55.1%
zip	15.6%
zoo	19.2%

As predicted lzo wins the decompression by a long margin. Sit on the other hand performs very poorly. This may be a programming fault, but having 500% higher than average decompression times is pathetic. Bz2 doesn't keep up with the rest either.

Winners

First Place: 7-zip

I was pleasantly surprised that there is still area for improvement in the field. Certainly the compression time may be long but the file size reduction more than makes up for it. Take for example the Linux kernel. Currently distributed using bz2 (which scored second best in size on the linux benchmark). Taking 3 minutes longer to compress, 7z will cut 1 Megabyte off the archive size and save each person decompressing it 11 seconds. And the rom files which are currently are distributed in zips would cut the archive from 24Mb down to 10Mb. And most importantly the project is open source (LGPL).

Shared Runners-up: Ace, Bzip2 and Rar

Bz2 and rar seem on par and there isn't much to distinguish between them. Bz2 is open and compresses slightly tighter. Rar has better decompression times. Ace on the other hand is a bit more annoying as it only comes with a decompresser on unix but it is reasonably fast. It is nice to see that open source solutions seem to surpass commercial software and here bz2 even with its stream based input still manages to keep up with the best commercial software.

Distinction: LZO

LZO was designed for embedded systems which do not have as much memory or processing power as desktop PCs. In decompression it run at 120Mb per second compared to bz2 which runs at just 4Mb/s. Very interesting and ideal for those embedded applications where the overhead of adding a gzip style library to the system would defeat the point of using compression in the first place.