Re: Random data cannot be compressed

On Thu, 06 Mar 2008 17:48:34 -0800, Ron Garret <rNOSPAMon@[EMAIL PROTECTED]
>
wrote:

>I finally got fed up with having to repeat myself all the time so I put 
>up a set of slides that explains all this:
>
>http://www.flownet.com/ron/halting_problem.pdf
>
>This is an old presentation, and some of these slides are not on point 
>so you might want to skip ahead and start with slide 12.

Look, I have no vested interest in the (in)compressibility of random
data. This whole discussion is nonsense about nonsense. I am well aware
of the definitions of randomness and why random data cannot be
compressed in general (and also why no compression algorithm can
compress all data sets). The only reason that I got involved at all is
because Richard is playing you, and probably laughing his head off while
at it. I was merely trying to explain _how_ he was playing you, so that
you'd have a way to fight back. But you just can't seem to understand
that the whole thing is semantic legerdemain.

WHEREAS: You're completely missing the point. This isn't about
compressing random data IN GENERAL. This is about compressing a SPECIFIC
data set, which happens to have been created using a random process.

In the following, D is a constant that has exactly the same value as the
"plain text" that we wish to compress. Given any plain text (randomly
generated or not), we can obviously create a constant D that has that
plain text as its value.

Here is the algorithm (pseudocode) to compress it to one bit:

 IF plainText = D THEN
   return 1
 ELSE
   return 0
 ENDIF

And here's the associated decompression algorithm:

 IF compressedData = 1 THEN
   return D
 ELSE
   return ""
 ENDIF

Do you get it now? For every SPECIFIC data set, we create a new pair of
SPECIFIC compression and decompression algorithms. Yes, it's
meaningless. That's what I've been trying to say all along.

Steve Schafer
Fenestra Technologies Corp.
http://www.fenestra.com/