Neil Turner's Blog

Blogging about technology and randomness since 2002

7-Zip

In boredom, I wrote a small VBScript document that wrote a file with the words to ’10 Green Bottles’, except you could set the initial number. Using 7500 as the initial number, I ended up with a 1.24MB text file, with the first 7500 lines of the song…

Anyway, as an experiment, I applied various compression methods to the file to see which one could make it the smallest. Here are my results:
(added RAR, GnomeZip and BZip2)

Comparison of zip formats
FormatSizeRatio
Original file.TXT1272 KB100%
WinZip 8.1.ZIP64.2KB5.05%
7-Zip 2.30 beta 24.ZIP57.8KB4.54%
7-Zip 2.30 beta 24.GZ57.8KB4.54%
ICEOWS 4.10.ICE33.8KB2.66%
WinRAR 3.10 beta 2.RAR33.8KB2.66%
7-Zip 2.30 beta 24.bz226.0KB2.04%
7-Zip 2.30 beta 24.7Z10.1KB0.79%

No, I couldn’t believe it either. I’ve always had good results from 7-Zip, particularly when using the 7z format. What annoys me is that 7-Zip is open source, released under the LGPL. Anyone could use this code in their own programs; so why do they not bother?

The performance of BZip2 also impressed me, though I was expecting more from the RAR format; even when optimised for text files, it still only equaled the performance of ICE. This is especially poor as WinRAR is Shareware and is one of only a handful of programs able to create RAR files. In all cases the compression was set to maximum.

The performance of the ICE format, which is apparently optimised for text files, is promising, but is still beaten by 7z.

5 Comments

  1. Have you tried the RAR format? I just compared 7-ZIP to WinZip and WinRAR, and in all the cases I tried, RAR came out tops, followed by 7Z, then ZIP.
    You can find WinRAR at http://www.rarsoft.com/ .
    – Ciaran.

  2. What setting did you have WinZip on? When you create a new archive, you have the Compression options of ‘Maximum (slowest)’, ‘Normal’, ‘Fast’, ‘Super fast’ and ‘None’.

  3. The other cool thing is they let me have the old command line version that I could stick on a floppy and use from any pc without having to install any software!

  4. In all cases where there was an option to set compression levels, I used maximum. I’ve updated it now.
    Ciaran – strange; RAR didn’t come out that well here. Maybe it depends on the file set.

  5. I got 7-zip 2,but i can’t get that good result of it.(have turned compres. 2 maximum(best))if anyone vcan help me i will really appreciate that,and by the way,what i#m trying 2 ‘zip’ are 6 xvid-video files,ca.200mb per file…..