On Friday 01 Aug 2003 16:32, Tom Kaitchuck wrote:

> To clarify things, I arrived at my numbers by taking a hypothetical size
> index between 1 and 2 units. For the values between 1 and 1 + 1/8 zips
> would compress the file into a file of size .25 and above that could go to
> size .5. For Bzips, anything below 1.5 would go to .25 and everything above
> would go to .5. So, assuming random samples: Bzip results in one notch
> improvement 3/8Th's of the time. Zips will use ~23% the bandwidth of
> uncompressed files, and bzips use 18.75% as much. (or 80% as much as the
> zips.)

OK, I see how you reached the figures.

There is another potential issue. The compression we are discussiong here is 
per file, not for a whole archive. ZIP performaed worse on the archive 
because it compresses each file separately, the archives them all together. 
This is inherently less efficient, and it skewed your test somewhat in favour 
of gzip/bzip2.

The fairer test would be to toar the entire directory and the zip -9 that. 
What is the difference then? The most relevant test would be to actually 
compress each file separately in every case, and see the relative compression 
ratios on all files. That is what is going to be happening in the node.

I think the edge of bzip2 may go down in that case, but I am not sure by how 
much.

Gordan
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