Re: [tlug] Compression Comparison (WAS: Tip of the Day: "ghosting" a machine with nc and dd)

[Nguyen Vu Hung <vu-hung@example.com>]

Daniel A. Ramaley さんは書きました:
> On Tuesday 17 July 2007 14:01, Stuart Luppescu wrote:
>   
> > Compressor     Compresssed             Time
> >               File Size
> > ----------     ------------           --------
> > bzip2           146,586                0.914
> > bzip2 -9        146,586                0.868
> >
> > These results rather surprised me, especially the comparison of bzip2
> > and bzip2 -9, so I decided to try it on another machine.
> >     
>
> Did you perform the tests in the order you listed them? It is likely 
> that the first run is slightly slower because the file has to be read 
> from disk, whereas for subsequent tests it would be in cache. When 
> testing speed i usually use files of at least a few hundred MB and/or 
> take the average of several trials to reduce the effects of caching.
>   
In general, compression ration and compression performance are trade-off.
The compression algorithms are different in gzip and bzip2.

Another thing is that the nature of the data to be compressed matters.
If you want to "benchmark" bzip2 and gzip, I would recommend the
combinations of following cases:

1. Test data: text files ( random or having pattern ), binary ( 
unstriped ),
  compressed by another algorithm.

Then compare their compression time, the resources that they needs, 
compression ration.

I already did a small "research" on this topic and posted to tlug ( but 
onone had replied ).

Dig tlug archive or search my blog ( http://360.yahoo.com/vuhung16 )

gl hfa,

VH