On Mon, Jul 09, 2007 at 09:15:07PM +0100, Andrew Coppin wrote: > Bulat Ziganshin wrote: >> Hello Andrew, >> >> Sunday, July 8, 2007, 7:07:59 PM, you wrote: >> >> i don't think that ppm is so complex - it's just probability of >> symbol in some context. it's just too slow in naive implementation >> >> > > Oh, sure, the *idea* is simple enough. Trying to actually *implement* it > correctly is something else... ;-)
Took me about an hour and 50 lines of code (about a year ago - this was one of my first Haskell programs) to implement a PPM (de)compressor that didn't crash, always generated the same output as input, and achieved 50% ratios on its own source code (not quite as good as gzip, but what do you expect from a completely untuned compressor?). Peak throughput: 2 bits / sec. :) >> the jhc is very different story > > Yes - last I heard, it's an experimental research project rather than a > production-ready compiler... Correct. It requires 5 minutes and 600MB of RAM to compile Hello, World, and fails with internal pattern match errors on anything significantly larger. Stefan
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