Which zipping algorithm is best for text files

April 1st, 2009 by Ben Carigtan | File in: Windows XP Tips

As a computer professional I deal with a lot of huge log files in text format. Sometimes deleting those log files is not an option so I need to archive them preferably on a compressed format so they won’t occupy too much space. As I tried 7-Zip, I found out that you can set the specific algorithm for zipping easily by right clicking the file then adding it to the 7-Zip archive:

The 7-Zip window will appear where you can set the compression level and the compression method (i.e. algorithm):

There are 3 compression methods available [info taken from Wikipedia]:

PPMd – a PPM-based algorithm. This algorithm is mostly based on Dmitry Shkarin’s PPMdH source code. PPMd provides very good compression ratio for plain text files. There is no difference between compression speed and decompression speed. Memory requirements for compression and decompression also are the same.
LZMA – algorithm based on Lempel-Ziv algorithm. It provides very fast decompression (about 10-20 times faster than compression).
BZip2 – this algorithm has efficiency is surpassed by PPM algorithms. bzip2 gets within ten to fifteen percent of PPM, while being roughly twice as fast at compression and six times faster at decompression. LZMA is generally more efficient than bzip2, while having generally 4x faster decompression.

For comparative purpose, I sort the output files on ascending file size:

You can see that the output files are less than 1% smaller than the original file (log.mo witha size of 119MB). The LZMA format generated the smallest file but the difference with the supposedly “worst” algorithm (BZip2) is a negligible 267KB (1414KB – 1147KB). The LZMA compression on Ultra mode took about a minute longer than BZip2. So remember that you could get more space efficiency in the expense of compression time. If you are in a hurry use BZip2. If you need to get the most compressed size, use LZMA.

The generated files are compatible with WinZip and WinRar. You can decompress or unpack a 7z file using WinZip or WinRar if the receiving party does not have 7-Zip installed.