compression algorithm!

[Peter Corlett]

On Wed, Apr 08, 2009 at 10:43:34AM +0100, Paul Makepeace wrote:
> abhishek jain <abhishek.netjain at gmail.com> wrote:
>> Hi Friends,I have a task to discover or search for a compression
>> algorithm which compresses even 300 - 400 characters to about at least
>> 200-300% compression reducing them to 150 characters.
[...]
> One solution to this is to concatenate your files and then compress as one.

"150 characters" suggests that it might be distinct messages rather than
files, that these are to be sent over SMS or some other expensive
transmission medium, and these are to be compressed to reduce costs.
Concatenation would be inappropriate in that case as the messages would not
be sent in a timely manner, and some means of ordering the messages would be
required.

One other feature of general-purpose lossless compression schemes is that
the output size is going to vary depending on the complexity of the input.
This makes it somewhat tricky to say "I want to compress losslessly to 150
characters". You can lossily compress to 150 characters in a SMS of course:
it's called txtspeak.

The problem, as stated, is intractible. Rather than struggle along trying to
solve it, one should step back and reconsider that requirement and how some
other part of the greater system could be engineered to make it easier. I'd
consider using UDP datagrams over GPRS, for example.

As a side-note, you can't send 160 eight bit characters in a single SMS as
it uses a seven bit coding. You can send eight and sixteen bit messages, but
you get fewer characters.