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Re: Algorithm that makes maximum compression of completly diffused data.

References <205bfa4f-29de-43de-be5a-72a12d77d0c9@googlegroups.com> <mailman.1835.1383162420.18130.python-list@python.org> <c73c8aa6-cac4-4f02-ae83-31cea167c172@googlegroups.com> <s9ra79dvvnd01rpuqg9hfh6bija8u2q49h@4ax.com> <5275c065$0$29972$c3e8da3$5496439d@news.astraweb.com>
Date 2013-11-03 15:10 +1100
Subject Re: Algorithm that makes maximum compression of completly diffused data.
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Message-ID <mailman.1965.1383451840.18130.python-list@python.org> (permalink)

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On Sun, Nov 3, 2013 at 2:17 PM, Steven D'Aprano
<steve+comp.lang.python@pearwood.info> wrote:
> There is a way to apparently get around these limits: store data
> externally, perhaps inside the compression application itself. Then, if
> you just look at the compressed file (the "data.zip" equivalent, although
> I stress that zip compression is *not* like this), you might think it has
> shrunk quite a lot. But when you include the hidden data, the compression
> is not quite so impressive...

Storing externally is, of course, a very useful thing - it's just not
compression. For instance, a git repository (and quite likely a
Mercurial one too) keeps track of files as blobs of data referenced by
their cryptographic hashes. The current state of a directory can be
described by listing file names with their object hashes, which is a
very compact notation; but it doesn't have _all_ the information, and
the "decompression" process involves fetching file contents from the
library. It's a tool in the arsenal, but it's not compression in the
same way that PK-ZIP is.

With real compression algorithms, there's usually an "out" clause that
detects that the algorithm's doing a bad job. The file format for
PK-ZIP and, I expect, every other archiving+compression file format,
has allowances for some of the files to be stored uncompressed. That
way, there's no need for any file to be enlarged by more than some
signature - say, a one-byte "compression type" marker, or even a
one-bit mark somewhere. But enlarged they must be, for the reasons
Steven explained.

ChrisA

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Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 11:21 -0700
  Re: Algorithm that makes maximum compression of completly diffused data. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-30 18:53 +0000
    Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 12:01 -0700
      Re: Algorithm that makes maximum compression of completly diffused data. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-30 19:18 +0000
        Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 12:22 -0700
          Re: Algorithm that makes maximum compression of completly diffused data. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-30 19:31 +0000
        Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 12:23 -0700
          Re: Algorithm that makes maximum compression of completly diffused data. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-30 19:35 +0000
          Re: Algorithm that makes maximum compression of completly diffused data. Ethan Furman <ethan@stoneleaf.us> - 2013-11-02 21:26 -0700
      Re: Algorithm that makes maximum compression of completly diffused data. Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-10-30 20:28 +0100
      Re: Algorithm that makes maximum compression of completly diffused data. Joshua Landau <joshua@landau.ws> - 2013-10-30 21:30 +0000
        Re: Algorithm that makes maximum compression of completly diffused data. rusi <rustompmody@gmail.com> - 2013-10-31 05:54 -0700
      Re: Algorithm that makes maximum compression of completly diffused data. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-10-30 21:52 +0000
      Re: Algorithm that makes maximum compression of completly diffused data. Tim Chase <python.list@tim.thechases.com> - 2013-10-30 18:01 -0500
      Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-10-31 10:41 +1100
  Re: Algorithm that makes maximum compression of completly diffused data. Dan Stromberg <drsalists@gmail.com> - 2013-10-30 12:29 -0700
  Re: Algorithm that makes maximum compression of completly diffused data. Tim Delaney <timothy.c.delaney@gmail.com> - 2013-10-31 06:35 +1100
    Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 12:47 -0700
  Re: Algorithm that makes maximum compression of completly diffused data. Modulok <modulok@gmail.com> - 2013-10-30 13:46 -0600
    Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 12:47 -0700
      Re: Algorithm that makes maximum compression of completly diffused data. Gene Heskett <gheskett@wdtv.com> - 2013-10-30 16:32 -0400
      Re: Algorithm that makes maximum compression of completly diffused data. Tim Roberts <timr@probo.com> - 2013-11-02 14:31 -0700
        Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-11-02 14:37 -0700
        Re: Algorithm that makes maximum compression of completly diffused data. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-03 03:17 +0000
          Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-03 15:10 +1100
          Re: Algorithm that makes maximum compression of completly diffused data. Joshua Landau <joshua@landau.ws> - 2013-11-03 15:34 +0000
          Re: Algorithm that makes maximum compression of completly diffused data. Joshua Landau <joshua@landau.ws> - 2013-11-03 15:51 +0000
          Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-11-03 19:40 -0800
          Re: Algorithm that makes maximum compression of completly diffused data. Tim Chase <python.list@tim.thechases.com> - 2013-11-04 07:08 -0600
        Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-11-04 05:53 -0800
          Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-11-04 06:00 -0800
          Re: Algorithm that makes maximum compression of completly diffused
 data. Dave Angel <davea@davea.name> - 2013-11-04 08:27 -0600
            Re: Algorithm that makes maximum compression of completly diffused data. rusi <rustompmody@gmail.com> - 2013-11-04 06:46 -0800
            Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-11-04 14:34 -0800
              Re: Algorithm that makes maximum compression of completly diffused
 data. Dave Angel <davea@davea.name> - 2013-11-04 19:29 -0600
              Re: Algorithm that makes maximum compression of completly diffused data. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-05 04:33 +0000
                Re: Algorithm that makes maximum compression of completly diffused data. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-05 04:36 +0000
          Re: Algorithm that makes maximum compression of completly diffused data. Tim Roberts <timr@probo.com> - 2013-11-07 00:05 -0800
            Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-11-07 10:59 -0800
            Re: Algorithm that makes maximum compression of completly diffused data. Tim Roberts <timr@probo.com> - 2013-11-07 11:22 -0800
            Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 09:26 +1100
              Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-11-07 18:05 -0800
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 13:17 +1100
                Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-11-07 18:25 -0800
                Re: Algorithm that makes maximum compression of completly diffused data. rusi <rustompmody@gmail.com> - 2013-11-07 18:36 -0800
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 13:36 +1100
                Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-11-07 18:43 -0800
                Re: Algorithm that makes maximum compression of completly diffused data. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-08 04:47 +0000
                Re: Algorithm that makes maximum compression of completly diffused   data. Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2013-11-08 20:09 +1300
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 18:21 +1100
                Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-11-08 07:48 -0800
                Re: Algorithm that makes maximum compression of completly diffused data. rusi <rustompmody@gmail.com> - 2013-11-08 07:57 -0800
                Re: Algorithm that makes maximum compression of completly diffused data. Ian Kelly <ian.g.kelly@gmail.com> - 2013-11-08 11:48 -0700
                Re: Algorithm that makes maximum compression of completly diffused data. "R. Michael Weylandt <michael.weylandt@gmail.com>" <michael.weylandt@gmail.com> - 2013-11-07 21:43 -0500
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 14:05 +1100
                Re: Algorithm that makes maximum compression of completly diffused data. Roy Smith <roy@panix.com> - 2013-11-07 22:08 -0500
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 14:24 +1100
                Re: Algorithm that makes maximum compression of completly diffused data. "R. Michael Weylandt <michael.weylandt@gmail.com>" <michael.weylandt@gmail.com> - 2013-11-07 23:05 -0500
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 15:06 +1100
                Re: Algorithm that makes maximum compression of completly diffused
 data. Dave Angel <davea@davea.name> - 2013-11-07 22:12 -0600
                Re: Algorithm that makes maximum compression of completly diffused data. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-08 05:32 +0000
                Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-11-07 18:24 -0800
                Re: Algorithm that makes maximum compression of completly diffused   data. Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2013-11-08 20:16 +1300
                Re: Algorithm that makes maximum compression of completly diffused data. Chris Angelico <rosuav@gmail.com> - 2013-11-08 13:27 +1100
      Re: Algorithm that makes maximum compression of completly diffused data. Ethan Furman <ethan@stoneleaf.us> - 2013-11-02 21:26 -0700
      Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-11-02 23:09 -0700
      Re: Algorithm that makes maximum compression of completly diffused data. Michael Torrie <torriem@gmail.com> - 2013-11-03 08:14 -0700
    Re: Algorithm that makes maximum compression of completly diffused data. jonas.thornvall@gmail.com - 2013-10-30 12:49 -0700
  Re: Algorithm that makes maximum compression of completly diffused data. Grant Edwards <invalid@invalid.invalid> - 2013-10-30 21:18 +0000
  Re: Algorithm that makes maximum compression of completly diffused data. Mark Janssen <dreamingforward@gmail.com> - 2013-10-30 14:26 -0700
  Re: Algorithm that makes maximum compression of completly diffused data. Dave Angel <davea@davea.name> - 2013-10-31 03:22 +0000
  Re: Algorithm that makes maximum compression of completly diffused data. Gene Heskett <gheskett@wdtv.com> - 2013-11-03 04:50 -0500

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