Compression - Re: Quantized Indexing Source Code (update & alg. history)

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Re: Quantized Indexing Source Code (update & alg. history)

Matt Mahoney

2006-01-10, 9:55 pm

Matt Mahoney wrote:
> David A. Scott wrote:
>
> There is some room for improvement. I tried compressing 10,000,000
> bytes of random charaters A, B, C. fpaq0 compresses it to 1,982,988
> bytes. The theoretical limit is 1/8 lg 3 = 1,981,203, a difference of
> 1785 bytes. For 1,000,000 bytes it compresses to 198,322 bytes, a
> difference of 201.7 bytes.
>
> -- Matt Mahoney

I posted fpaq1.cpp to
http://www2.cs.fit.edu/~mmahoney/compression/#fpaq0
It is an improved order 0 arithmetic coder using 64 bit arithmetic. On
a 10MB file which repeats "ABC" it is 25 bytes over the theoretical
limit, and I believe most of this is due to approximations made by the
model early in compression.

-- Matt Mahoney

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