Re: [Monotone-devel] Re: results of mercurial user survey

[Nathaniel Smith]

On Sun, Apr 30, 2006 at 10:45:16PM -0700, Graydon Hoare wrote:
> Nathaniel Smith wrote:
> 
> >Plus it's totally non-streamable :-).  You'd basically end up doing
> >exactly what we do now, since bzip2 operates on blocks (hence the
> >"b")...
> 
> Eh, I'm not sure I really agree with this interpretation. As far as I 
> know, most compressors operate on (possibly padded) blocks; the only 
> things I mean by "streaming" are:
> 
>  - There's some retained state in the compressor, between blocks.
>  - The block size is unrelated to natural transmission units, hence you
>    need some secondary interaction between the transmission protocol and
>    the compressor to ensure proper flushing.

Sure.  But these aren't true for a BWT compressor, because BWT
scrambles a whole block at a time; you can't do BWT or inverse-BWT
until you have an entire block to work with at once.  And no state is
retained between blocks (unless you're tacking on an adaptive huffman
coder or something, but anyway, that's relatively trivial).

> (I always thought the "b" in "bzip2" was for "Burrows-Wheeler", but I 
> might be wrong; wikipedia suggests that bzip -- the ancestor to bzip2 -- 
> used arithmetic coding, so maybe it just stands for "better". Perhaps we 
> should ask Julian :)

Hmm, I was thinking it stood for "block sorting".  Your theories are
plausible too, though :-)

Umm.  Right.  Should probably get back to doing vaguely on-topic
things, shouldn't I?  I guess this little tangent is probably
educational for someone or t'other out there, anyway :-)

-- Nathaniel

-- 
Eternity is very long, especially towards the end.
  -- Woody Allen