[Gllug] Re: [linuxjobs] Cypher: help requested

[Rich Walker]

Chris Bell <chrisbell at overview.demon.co.uk> writes:

> On Tue 01 Jun, Jim Bailey wrote:
>> 
>> On Jun 01, 11:31, Andrew Halliwell wrote:
>> > So, an infinity:1 compression ratio for ITV then... (as compressing an
>> > entire night's viewing would result in a zero length file)
>> 
>> I don't think so, IANAM but some very odd things happen when
>> mathematicians start messing about with infinity.  Maybe a mathematician
>> could shed some light on it.

I am a trained mathematician, but I've never played one on TV.

>From an information-theoretic point of view, there is zero information
to begin with in 24 hours of ITV (You're expecting all of it, so no
information is conveyed - there are no surprises).

Hence, it should be possible to compress the whole thing down to the
statement "You watched ITV for 24 hours". 

Applying standard compression algorithms to this statement:
rw at thoth:rw 942M : echo "You watched ITV for 24 hours" | gzip -9vc | wc
 -6.9%
      0       2      49
rw at thoth:rw 942M : echo "You watched ITV for 24 hours" | bzip2 -9vc | wc
  (stdin):  0.397:1, 20.138 bits/byte, -151.72% saved, 29 in, 73 out.
      0       5      73
rw at thoth:rw 942M : echo "You watched ITV for 24 hours" | wc
      1       6      29
rw at thoth:rw 942M :

So, no compression is better than telling someone they watched ITV.

>> 
>> Peace Jim
>
>    In this case you could try using calculus to determine the rate of change
> of compressed file size as the input file time/length approaches the day
> time/length.

Note that, since ITV contains no information, d(compressed)/dt is
proportional to log(t):

You watched ITV for 24 hours   - 29
You watched ITV for 168 hours  - 30
You watched ITV for 8760 hours - 31

Hmm. Maybe I've unravelled his compression algorithm.

cheers, Rich.


>
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> Chris Bell
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