Beyond gzip

Dan Ingalls Dan.Ingalls at disney.com
Sun May 27 05:07:24 UTC 2001


I wrote...
>> Hmm.  Should be easy to do.  Also, easy to find out how much 
>> it will help.  I'll just zap the hashes in a normal image and 
>> see how much better it compresses.
>
A. wrote...
>I don't think you'll see a lot of improvement unless you go a step further.
>What I tried was re-ordering the objects so that they're arranged by class
>and by size (and for some others even by intrinsic ordering such as
>strings). This is important because LZ compressors won't look beyound
>certain distances (and also the smaller the distance, the better the
>compression). Here's one thing you could try to see a bit of this effect:
>Create an image segment that contains all Strings in the image in
>lexicographical order. Write this IS; try to compress it. Now dump the hash
>bits and try again.

Good idea.

In this same vein, you can see where I was going with pointer locality.  It would be a very quick loop to make every pointer reference be self-relative, which might well give us a bunch of small numbers, meaning lots of zeroes, and hence better compression.

Actually I was trying to give this project away.
Therefore (and for a couple of other reasons ;-), I promise not to do anything on it for a week.

;-)
	- Dan






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