build index.html for all winners
Updated manifest as per recent file changes. Updated winner `.winner.json` to reflect the manifest changes. Added [bin/all_run.sh](bin/all_run.sh) tool to run a command over all winning entries. These tools had slight improvements in the help usage message: * bin/gen-author.sh VERSION="1.3.1 2024-01-16" * bin/gen-inventory.sh VERSION="1.0.1 2024-01-16" * bin/pandoc_wrapper.sh VERSION="1.3.1 2024-01-16" * bin/subst.default.sh VERSION="1.1.1 2024-01-16" * bin/subst.winner-index.sh VERSION="1.1.1 2024-01-16" The `bin/readme2index.sh` tool was improved so that if the `index.html` file exists and the tool forms the exact same content, then the file `index.html` file is NOT touched. * bin/readme2index.sh VERSION="1.1 2024-01-16" We used the following command to generate `index.html` files for all winning entries: ```sh bin/all_run.sh -v 3 bin/readme2index.sh ``` NOTE: We have not (yet) built HTML files above the winner directory level (e.g., no year level nor top level HTML), nor have be built non-index HTML files for winners. NOTE: By default we are running `pandoc(1)` with: ``` --fail-if-warnings=true ``` This means that any problems with markdown to HTML generates an error. This is done to be sure that the HTML conversion is clean. We had to fix the following `README.md` files: * `2000/rince/README.md` The reference [^2] was never used. We made a guess that [^2] applies to the same spot as [^1]. Perhaps there is a better spot where [^2] applies? NOTE: For every reference, there MUST be some place where that reference is used. * 2012/vik/README.md The string "$...$" is assumed to be a TeX encoded string. NOTE: Every "$..$" needs to be backslashed as in "\$..\$". * 2018/burton1/README.md The reference [2] was duplicated. We changed the second [2] to [3]. NOTE: Every reference needs to have a unique number. * 2020/carlini/README.md The string "$...$" is assumed to be a TeX encoded string. NOTE: Every "$..$" needs to be backslashed as in "\$..\$". We also found 2 errors in the `author/author_handle.json` file set: * author/Anonymous_2001.json The `author/Anonymous_2001.json` file was missing. * author/Jari_Arkko.json The winner ID for `1989_jar.1` had a typo.
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<!DOCTYPE html>
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
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<!-- START: two lines up starts content from: inc/top.default.html -->
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<!-- -->
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<!-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
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<!-- !!! DO NOT MODIFY THIS FILE - This file is generated by a tool !!! -->
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@@ -6,27 +8,464 @@
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<!-- !!! DO NOT MODIFY THIS FILE - This file is generated by a tool !!! -->
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<!-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! -->
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<!-- -->
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<!-- file: 2000/bmeyer/index.html created by: fake.gen_index.sh version: 1.0.5 2023-10-31 -->
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<html lang="en">
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<!-- END: this line ends content from: inc/top.default.html -->
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<!-- -->
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<!-- This file was formed by the tool: bin/readme2index.sh version: 1.1 2024-01-16 -->
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<!-- -->
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<!-- START: this line starts content from: inc/head.default.html -->
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>2000 bmeyer</title>
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<meta name="description" content="IOCCC year: 2000 IOCCC winner: bmeyer winner index page">
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<meta name="keywords" content="IOCCC,2000,bmeyer,winner index page">
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<link rel="stylesheet" href="/temp-test-ioccc/ioccc.css">
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<meta charset="utf-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
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<title>2000/bmeyer</title>
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<meta name="description" content="2000 IOCCC winner bmeyer">
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<meta name="keywords" content="IOCCC, 2000, IOCCC 2000, IOCCC winner, bmeyer">
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</head>
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<!-- END: this line ends content from: inc/head.default.html -->
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<!-- START: this line starts content from: inc/body.default.html -->
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<body>
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<h1>2000 bmeyer</h1>
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<!-- END: this line ends content from: inc/body.default.html -->
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<!-- START: this line starts content from: inc/header.default.html -->
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<p>XXX - fake content until readme2index is working - XXX</p>
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<div class="header">
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||||
<img src="/temp-test-ioccc/png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
|
||||
<h1>The International Obfuscated C Code Contest</h1>
|
||||
<h2>2000/bmeyer</h2>
|
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</div>
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<hr style="width:50%;text-align:left;margin-left:0">
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<!-- END: this line ends content from: inc/header.default.html -->
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<!-- START: this line starts content from: inc/topnav.mid.html -->
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<!-- Start Nu Html Checker -->
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<p><a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F2000%2Fbmeyer%2Findex.html">Nu Html check https://ioccc-src.github.io/temp-test-ioccc/2000/bmeyer/index.html</a></p>
|
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<!-- End Nu Html Checker -->
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||||
<div class="topnav">
|
||||
<a class="Left" href="../bellard/index.html">← bellard</a>
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<a class="Left" href="../index.html">↑ 2000 ↑</a>
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||||
<a class="Left" href="../briddlebane/index.html">briddlebane →</a>
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<a class="Right" href="#inventory">Inventory</a>
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</div>
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<!-- END: this line ends content from: inc/topnav.mid.html -->
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<!-- START: this line starts content from: inc/begin-row.default.html -->
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<div class="row">
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<div class="leftcolumn">
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<!-- END: this line ends content from: inc/begin-leftcolumn.default.html -->
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<!-- START: this line starts content from: inc/sidenav.default.html -->
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<div class="sidenav">
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<a href="#content">Jump to contents</a>
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</div>
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<hr>
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<div class="sidenav">
|
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<a href="/temp-test-ioccc/index.html">IOCCC Home</a>
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<a href="/temp-test-ioccc/years.html">Winning Entries</a>
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<a href="/temp-test-ioccc/winners.html">People who have won</a>
|
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</div>
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<hr>
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<div class="sidenav">
|
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<a href="/temp-test-ioccc/news.html">IOCCC News</a>
|
||||
<a href="/temp-test-ioccc/faq.html#submit">How to enter the IOCCC</a>
|
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<a href="/temp-test-ioccc/faq.html">FAQ</a>
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</div>
|
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<hr>
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<div class="sidenav">
|
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<a href="/temp-test-ioccc/bugs.html">Bugs & (mis)features</a>
|
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<a href="/temp-test-ioccc/faq.html#fix_a_winner">Fixing IOCCC winners</a>
|
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<a href="/temp-test-ioccc/faq.html#fix_web_site">Fixing the web site</a>
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<a href="/temp-test-ioccc/faq.html#fix_author">Fixing winner info</a>
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<a href="/temp-test-ioccc/thanks-for-help.html">Thanks for the help</a>
|
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</div>
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<hr>
|
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<div class="sidenav">
|
||||
<a href="/temp-test-ioccc/judges.html">The IOCCC Judges</a>
|
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<a href="/temp-test-ioccc/contact.html">Contacting the IOCCC</a>
|
||||
</div>
|
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<hr>
|
||||
<div class="sidenav">
|
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<a href="#top">Jump to top</a>
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</div>
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<!-- END: this line ends content from: inc/sidenav.default.html -->
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</div>
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<div class="rightcolumn">
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<!-- END: this line ends content from: inc/begin-rightcolumn.default.html -->
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<!-- START: this line starts content from: inc/before-content.default.html -->
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<a name="content"></a>
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<!-- END: this line ends content from: inc/before-content.default.html -->
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<!-- START: this line starts content generated by: bin/gen-author.sh -->
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<p><a name="author"><strong>Author:</strong></a> <br><br>Name: <a
|
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href="/temp-test-ioccc/winners.html#Bernd_Meyer">Bernd Meyer</a><br>
|
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Location: <a href="/temp-test-ioccc/location.html#AU">AU</a></p>
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<!-- END: next line ends content generated by: bin/gen-author.sh -->
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<h2 id="to-build">To build:</h2>
|
||||
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="fu">make</span></span></code></pre></div>
|
||||
<h2 id="to-use">To use:</h2>
|
||||
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./bmeyer</span></span></code></pre></div>
|
||||
<h2 id="try">Try:</h2>
|
||||
<p>In a video window (white text on black background):</p>
|
||||
<div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./try.sh</span></span></code></pre></div>
|
||||
<p>The script will suggest you compare the output of the program with
|
||||
images, prompting you to press any key to continue so that you may do
|
||||
so.</p>
|
||||
<h2 id="judges-remarks">Judges’ remarks:</h2>
|
||||
<p>Don’t even think of supplying different compression factors (the
|
||||
dashed argument) for compression and decompression! You’ve been
|
||||
warned.</p>
|
||||
<p>The author recommended on linux/x86, glibc 2.0, libc4/5:</p>
|
||||
<pre class="make"><code>bmeyer: bmeyer.c
|
||||
CC -DY="__setfpucw(0x127f)" -O6 $? -o $@ -lm</code></pre>
|
||||
<p>However many compilers use <code>-O3</code> as the maximum level for
|
||||
<code>-O</code> optimization.</p>
|
||||
<p>And on linux/x86, glibc 2.1:</p>
|
||||
<pre class="make"><code>bmeyer: bmeyer.c
|
||||
gcc -DY='int x=0x127f; __asm__ ("fldcw %0" : : "m" (*&x))' $? -o $@ -lm</code></pre>
|
||||
<p>Compile with the maximum possible optimization on your system. If
|
||||
your system has 80-bit internal representation of floating point values
|
||||
(x86, some Motorola processors) and you want the compressed format to be
|
||||
portable across platforms, you need to set your FPU to use 64 bit mode.
|
||||
Read the author’s remarks below for more details.</p>
|
||||
<p>If you cannot work out how to get into 64 bit mode, you can try using
|
||||
<code>-ffloat-store</code> if you compile with GCC (this may have a
|
||||
performance penalty). The resulting binary will have a good chance to
|
||||
produce portable files, but due to the resulting double-rounding (first
|
||||
internally set to 80 bit, then to 64 bit on writing the value to
|
||||
memory), there is a small but very real chance any given file produced
|
||||
might not be portable.</p>
|
||||
<p>The <a href="Makefile">Makefile</a> defaults to <code>-O3</code> and
|
||||
no <code>asm()</code> call.</p>
|
||||
<h2 id="authors-remarks">Author’s remarks:</h2>
|
||||
<p>This program is called <code>GLICBAWLS</code></p>
|
||||
<h4 id="function">Function</h4>
|
||||
<p><code>GLICBAWLS</code> stands for “Grey Level Image Compression By
|
||||
Adaptive Weighted Least Squares”.</p>
|
||||
<p>And that’s exactly what this program does — feed it a .PGM file
|
||||
(either raw [i.e. P5] or ASCII [i.e. P2]) on stdin, and it will output a
|
||||
compressed version to stdout. Feed it a compressed file on stdin, and it
|
||||
will decompress it to stdout — as either raw or ASCII .PGM, depending on
|
||||
what format it was compressed from. For example:</p>
|
||||
<div class="sourceCode" id="cb6"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./glicbawls</span> <span class="op"><</span> michael.pgm <span class="op">></span> michael.glic</span></code></pre></div>
|
||||
<p>and then</p>
|
||||
<div class="sourceCode" id="cb7"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./glicbawls</span> <span class="op"><</span> michael.glic <span class="op">></span> michael.decoded.pgm</span></code></pre></div>
|
||||
<p>As it turns out, <code>glicbawls</code> compresses greyscale images
|
||||
(or, more precisely, “natural” greyscale images) better than any other
|
||||
program I am aware of (with the exception of the not-yet-published
|
||||
program developed for my PhD thesis). Of course, this might take some
|
||||
time, so a progress indicator is provided. To make things more
|
||||
interesting, instead of a boring bar or percentage display, an ASCII
|
||||
rendition of the image being compressed/decompressed is output to
|
||||
<code>stderr</code> (assuming white text on black background). If you
|
||||
have trouble recognizing the image, try squinting at it ;-).</p>
|
||||
<p>If you still have trouble, simply use a terminal or xterm with more
|
||||
than 80 columns, and tell <code>glicbawls</code> about it by giving the
|
||||
number of columns as an argument. For example</p>
|
||||
<div class="sourceCode" id="cb8"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./glicbawls</span> 260 <span class="op"><</span>lavabus.pgm <span class="op">></span>lavabus.glic</span></code></pre></div>
|
||||
<p>will allow <code>glicbawls</code> to use up to 260 columns, which
|
||||
makes things much more recognizable.</p>
|
||||
<p>Still running out of space? Need to compress those images just a tad
|
||||
more? And maybe you can handle some loss due to the compression? If so,
|
||||
you can use <code>glicbawls</code>’ “near lossless” compression mode. In
|
||||
that mode, the decoded pixel values are allowed to differ from the
|
||||
originals, but there is an upper limit on the magnitude of the
|
||||
difference. For example, if a maximum error of 2 is allowed, an original
|
||||
pixel value of 37 could be decoded as 35, 36, 37, 38 or 39. In order to
|
||||
use this mode, simply give the maximum allowed error as an argument,
|
||||
with a dash (<code>-</code>) before it. For example:</p>
|
||||
<div class="sourceCode" id="cb9"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./glicbawls</span> <span class="at">-2</span> <span class="op"><</span> graph.pgm <span class="op">></span> graph.2.glic</span></code></pre></div>
|
||||
<p>will compress in a way that allows decompression with a maximum error
|
||||
of two. You can combine both types of arguments, i.e.:</p>
|
||||
<div class="sourceCode" id="cb10"><pre
|
||||
class="sourceCode sh"><code class="sourceCode bash"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./glicbawls</span> <span class="at">-3</span> 180 <span class="op"><</span> graph.pgm <span class="op">></span>graph.3.glic</span></code></pre></div>
|
||||
<p>will compress with a maximum error of 3, using a 180 column terminal
|
||||
for the progress display, and:</p>
|
||||
<div class="sourceCode" id="cb11"><pre
|
||||
class="sourceCode sh"><code class="sourceCode bash"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true" tabindex="-1"></a><span class="ex">./glicbawls</span> <span class="at">-3</span> 180 <span class="op"><</span> graph.3.glic <span class="op">></span> graph.3maxerr.pgm</span></code></pre></div>
|
||||
<p>will decompress the result on such a terminal.</p>
|
||||
<p>But wait, there is more — you can also feed <code>glicbawls</code>
|
||||
.PPM files (i.e. colour images), raw or ASCII, your choice.
|
||||
<code>glicbawls</code> will compress and decompress them just fine.
|
||||
However, it only does “reasonably well” on them; It beats PNG easily,
|
||||
but there are certainly programs out there that can compress colour
|
||||
images considerably better. And don’t even <em>think</em> about using it
|
||||
for so-called “artistic” images (i.e. anything that wasn’t scanned from
|
||||
a photo or camera)….</p>
|
||||
<h3 id="warning">WARNING</h3>
|
||||
<p><code>glicball</code> is rather CPU and FPU intensive. Don’t run it
|
||||
on anything slow. Things start to be usable around 300+MHz, with 600+
|
||||
being highly desirable.</p>
|
||||
<h3 id="compile-instructions">Compile Instructions</h3>
|
||||
<p>Unlike most compression program, <code>glicbawls</code> makes heavy
|
||||
use of floating point maths — and not all FPUs are created equal. Most
|
||||
importantly, the x86 and 68k FPUs use 80 bit floating point formats
|
||||
internally, while most other processors use IEEE 64 bit formats by
|
||||
default. If not taken care of, this means that a <code>glicbawls</code>
|
||||
file compressed on one CPU cannot generally be decompressed on
|
||||
another.</p>
|
||||
<p>Fortunately, just about all current FPUs can be put into IEEE 64 bit
|
||||
mode (or at least something close enough for <code>glicbawls</code>).
|
||||
Unfortunately, there is no standard way of doing so. For this reason,
|
||||
the build file contains <em>three</em> compile lines; one for machines
|
||||
that already use 64 bit mode by default (most RISC processors), one for
|
||||
linux/x86 machines using libc4, libc5 or glibc2.0, and one for linux/x86
|
||||
machines using glibc2.1 (glibc2.1 no longer exports the
|
||||
<code>__setfpucw()</code> function, necessitating the use of gcc inline
|
||||
assembly. *Grumble*).</p>
|
||||
<p>So, if you are building on a machine that does not, by default, use
|
||||
IEEE 64 bit floating point doubles, you’ll have to define <code>Y</code>
|
||||
to be a command that switches it into that mode. If you fail to do so,
|
||||
your <code>glicbawls</code> executable will still be able to decompress
|
||||
its own compressed files, but you may be unable to exchange files with
|
||||
<code>glicbawls</code> on other machines.</p>
|
||||
<h3 id="obfuscation">Obfuscation</h3>
|
||||
<p>Most of the obfuscation of this program was driven by the desperate
|
||||
struggle to fit all of <code>glicbawls</code>’ features into code that
|
||||
fits the IOCCC’s size limits. All identifiers’ names are
|
||||
single-character, which was only possible by ruthless exploitation of
|
||||
scope. There is a function <code>M()</code> that handles nearly all
|
||||
input from <code>stdin</code>, handles all output to
|
||||
<code>stdout</code>, and also recursively calculates one of the
|
||||
mathematical expressions needed for error modelling. There is a function
|
||||
that calculates <code>(A^(-1)*b)*x</code> with <code>A</code> being a
|
||||
matrix and <code>b</code> and <code>x</code> being vectors, and does so
|
||||
in a very efficient way — but one would be hard pressed to find it.
|
||||
There is an arithmetic coder that is even less recognizable. A lot of
|
||||
loop variables don’t get initialized, but instead the code is arranged
|
||||
in such a way that they just happen to have the right value when control
|
||||
flow reaches the loops. Lots of functions use the same two global
|
||||
scratch variables. Variables change their meaning all the time, and the
|
||||
differences between compressing and decompressing are handled in rather
|
||||
subtle ways all over the program. The string that holds the ASCII values
|
||||
for displaying the progress image doubles as a description on how to
|
||||
find a pixel’s causal neighbours. And then there are a few
|
||||
<code>#define</code>s that really are just in there to save a few
|
||||
characters, but as an added “benefit” make the source ever more
|
||||
unreadable.</p>
|
||||
<p>In short — running it through the preprocessor and the pretty-printer
|
||||
will give you something that looks slightly less like line noise and
|
||||
slightly more like a C program, but unless you are a true wizard, it is
|
||||
unlikely to gain you any insights into what is actually going on….<a
|
||||
href="#fn1" class="footnote-ref" id="fnref1"
|
||||
role="doc-noteref"><sup>1</sup></a></p>
|
||||
<h3 id="bugs-assumptions-and-todo">Bugs, Assumptions and TODO</h3>
|
||||
<p><code>glicbawls</code> assumes that characters are 8 bit wide, and
|
||||
that the character set used is ASCII. If one of these isn’t true, all
|
||||
hell will break loose.</p>
|
||||
<p>The .PGM headers are not checked very thoroughly —
|
||||
<code>glicbawls</code> will happily try to encode lots of files that it
|
||||
shouldn’t touch. The old adage of “garbage in, garbage out” holds in
|
||||
that case. Furthermore, even if <code>glicbawls</code> detects an
|
||||
incorrect input, it fails to provide a meaningful error message, and
|
||||
instead simply aborts.</p>
|
||||
<p>When decompressing a near-lossless encoded image, the maximum allowed
|
||||
error is required as a command line parameter. This should really be
|
||||
saved in the compressed file!</p>
|
||||
<p><code>glicbawls</code> relies on the decimal representation of all
|
||||
integers having less than 255 digits. While ANSI C does not guarantee
|
||||
this, it seems rather unlikely that anyone in the foreseeable future
|
||||
would use images with <code>10^255</code> rows, columns or different
|
||||
levels of grey. Also, it is assumed that any integer used can be cast to
|
||||
a <code>double</code> and back without loss of precision. This limits
|
||||
the number of rows, columns and grey levels to 9 quintillion, which
|
||||
should also be sufficient for the next few years.</p>
|
||||
<p>There is a theoretical chance that you might get a division by zero
|
||||
error. You have a MUCH better chance of getting hit by lightning the
|
||||
very second you realize that you just won a few million in a lottery.
|
||||
But if it happens to you, don’t say I didn’t warn you! Instead, go out
|
||||
and buy a lightning rod and a lottery ticket ;-)</p>
|
||||
<p>At one point, a pointer to <code>int</code> is used as the target of
|
||||
a <code>"%1[#]"</code> conversion in a <code>scanf(3)</code>, which
|
||||
makes gcc rather unhappy, but shouldn’t really cause anyone any trouble.
|
||||
The same goes for a couple of assignments which are used as truth
|
||||
values.</p>
|
||||
<h3 id="algorithm">Algorithm</h3>
|
||||
<p>An exhaustive explanation of the algorithm used would go beyond the
|
||||
scope of an info file, and would also be quite difficult in pure ASCII,
|
||||
so the following is just a rough outline, and contains some
|
||||
compression-speak…</p>
|
||||
<p>The image is handled in <a
|
||||
href="https://en.wikipedia.org/wiki/Scan_line">scanline</a> ordering.
|
||||
For each pixel, an expected value is calculated by creating a least
|
||||
squares predictor of order 12 based on all of the previously
|
||||
encoded/decoded pixels. However, the contribution of each pixel is
|
||||
weighted according to its <a
|
||||
href="https://en.wikipedia.org/wiki/Taxicab_geometry">Manhattan-distance</a>
|
||||
from the current pixel, <code>D</code>. That weight used is
|
||||
<code>pow(0.8,D)</code>. <a href="#fn2" class="footnote-ref" id="fnref2"
|
||||
role="doc-noteref"><sup>2</sup></a> <a href="#fn3" class="footnote-ref"
|
||||
id="fnref3" role="doc-noteref"><sup>3</sup></a> <a href="#fn4"
|
||||
class="footnote-ref" id="fnref4" role="doc-noteref"><sup>4</sup></a></p>
|
||||
<p>In a similar way, the prediction <em>errors</em> for all previous
|
||||
pixels are combined — a weighted average (with weight
|
||||
<code>pow(0.7,D)</code>) of the squares of all previous prediction
|
||||
errors is taken, and the square root of the (appropriately scaled)
|
||||
result is called sigma.</p>
|
||||
<p>The predicted value and sigma are then used as the parameters of a <a
|
||||
href="https://en.wikipedia.org/wiki/Student%27s_t-distribution">Student
|
||||
or t-distribution</a> (which is similar to a <a
|
||||
href="https://en.wikipedia.org/wiki/Normal_distribution">normal
|
||||
distribution</a>, but has more weight in the tails), providing a <a
|
||||
href="https://en.wikipedia.org/wiki/Probability_distribution">probability
|
||||
distribution</a> for the current pixel.</p>
|
||||
<p>Next, the possible interval of values for the current pixel is
|
||||
halved, and through integration of the probability distribution, a
|
||||
probability is calculated for the pixel value being in the lower half.
|
||||
During encoding, the actual value is examined, and the result encoded
|
||||
using an arithmetic coder. During decoding, the arithmetic decoder
|
||||
provides the information which half the actual value is in. In both
|
||||
cases, the interval borders are adjusted accordingly, the arithmetic
|
||||
coder/decoder updated, and the interval halving repeated until the
|
||||
precise value has been en/decoded<a href="#fn5" class="footnote-ref"
|
||||
id="fnref5" role="doc-noteref"><sup>5</sup></a>.</p>
|
||||
<h3 id="photo-credit">Photo Credit:</h3>
|
||||
<p><a href="lavabus.pgm">Lavabus</a> was taken by the judge, Landon Curt
|
||||
Noll. <a href="michael.pgm">Michael</a> was provided by the author. <a
|
||||
href="lenna.glic">Lenna</a> is a 1972 Playboy centerfold (doesn’t show
|
||||
very much).</p>
|
||||
<ul>
|
||||
<li><p><a href="michael.pgm">michael.pgm</a></p>
|
||||
<p>The author’s Godchild and nephew.</p></li>
|
||||
<li><p><a href="lavabus.pgm">lavabus.pgm</a></p>
|
||||
<p>A bus that was trapped by lava from <a
|
||||
href="https://en.wikipedia.org/wiki/Kīlauea">Kilauea volcano</a> in
|
||||
Hawaii, US. Nobody was in the bus at the time, BTW. Photo date:
|
||||
1981.</p></li>
|
||||
<li><p><a href="lenna.glic">lenna.glic</a></p>
|
||||
<p>A November 1972 Playboy centerfold was scanned in long ago and has
|
||||
been used for image compression research since then. Playboy originally
|
||||
threatened to prosecute unauthorized use, but eventually granted that,
|
||||
having been in use for image compression testing for so long, it was now
|
||||
a useful benchmark. (Note: This picture doesn’t show very
|
||||
much.)</p></li>
|
||||
</ul>
|
||||
<h2 id="copyright-and-cc-by-sa-4.0-license">Copyright and CC BY-SA 4.0
|
||||
License:</h2>
|
||||
<p>This file is Copyright (c) 2023 by Landon Curt Noll. All Rights
|
||||
Reserved. You are free to share and adapt this file under the terms of
|
||||
this license:</p>
|
||||
<pre><code>Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)</code></pre>
|
||||
<p>For more information, see:
|
||||
https://creativecommons.org/licenses/by-sa/4.0/</p>
|
||||
<section id="footnotes" class="footnotes footnotes-end-of-document"
|
||||
role="doc-endnotes">
|
||||
<hr />
|
||||
<ol>
|
||||
<li id="fn1"><p>Yes, this could be seen as a challenge….<a
|
||||
href="#fnref1" class="footnote-back" role="doc-backlink">↩︎</a></p></li>
|
||||
<li id="fn2"><p>Actually, the weight is <code>pow(0.8,D)/s</code>, where
|
||||
<code>s</code> is the sigma used for encoding/decoding the particular
|
||||
previous pixel. Dividing by <code>s</code> is a rather arbitrary action
|
||||
justified only by the improvement in results. Mathematically, I can only
|
||||
justify dividing by <code>s^2</code>, or not dividing at all….<a
|
||||
href="#fnref2" class="footnote-back" role="doc-backlink">↩︎</a></p></li>
|
||||
<li id="fn3"><p>Obviously, these least squares predictors are not
|
||||
calculated from scratch for each pixel. Some clever reuse of earlier
|
||||
results allows <code>O(1)</code> calculation, rather than the
|
||||
<code>O(previous_rows*columns)</code> this description would suggest.<a
|
||||
href="#fnref3" class="footnote-back" role="doc-backlink">↩︎</a></p></li>
|
||||
<li id="fn4"><p>As anyone who has ever tried local least squares knows
|
||||
from bitter experience, there is a lot of numerical instability
|
||||
associated with them. So <code>glicbawls</code> adds a bias towards an
|
||||
averaging predictor to the equation system the least squares predictor
|
||||
is calculated from. The weight that is given to this bias is constantly
|
||||
adjusted throughout coding/decoding, thus justifying the ‘a’ in
|
||||
<code>glicbawls</code>.<a href="#fnref4" class="footnote-back"
|
||||
role="doc-backlink">↩︎</a></p></li>
|
||||
<li id="fn5"><p>In the case of near-lossless coding, the interval is not
|
||||
necessarily <em>halved</em>, but rather split at a convenient point (the
|
||||
split points are chosen in such a way as to minimise the expected number
|
||||
of bits needed for coding). Also, the iteration ends as soon as the
|
||||
interval is small enough to guarantee decoding within the requested
|
||||
maximum error.<a href="#fnref5" class="footnote-back"
|
||||
role="doc-backlink">↩︎</a></p></li>
|
||||
</ol>
|
||||
</section>
|
||||
<!-- START: this line starts content generated by: bin/gen-inventory.sh -->
|
||||
|
||||
<h1 id="inventory-for-2000bmeyer"><a name="inventory"></a>Inventory for
|
||||
2000/bmeyer</h1>
|
||||
<h2 id="primary-files">Primary files</h2>
|
||||
<ul>
|
||||
<li><a href="index.html">index.html</a> - winner home page</li>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/bmeyer.c">bmeyer.c</a>
|
||||
- winning source</li>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/Makefile">Makefile</a>
|
||||
- winner Makefile</li>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/bmeyer.orig.c">bmeyer.orig.c</a>
|
||||
- original source</li>
|
||||
<li><a href="lavabus.pgm">lavabus.pgm</a> - Kilauea volcano bus trapped
|
||||
in lava</li>
|
||||
<li><a href="michael.pgm">michael.pgm</a> - author’s Godchild and
|
||||
Nephew</li>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/try.sh">try.sh</a>
|
||||
- how to run</li>
|
||||
<li><a href="lenna.glic">lenna.glic</a> - P10 scan of 1972 Playboy
|
||||
centerfold</li>
|
||||
<li><a href="2000_bmeyer.tar.bz2">2000_bmeyer.tar.bz2</a> - download
|
||||
winning source</li>
|
||||
</ul>
|
||||
<h2 id="secondary-files">Secondary files</h2>
|
||||
<ul>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/.gitignore">.gitignore</a>
|
||||
- list of files that should not be committed under git</li>
|
||||
<li><a href=".path">.path</a> - directory path from top directory</li>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/.winner.json">.winner.json</a>
|
||||
- description of winner in JSON</li>
|
||||
<li><a
|
||||
href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2000/bmeyer/README.md">README.md</a>
|
||||
- markdown source for index.html</li>
|
||||
</ul>
|
||||
|
||||
<!-- END: next line ends content generated by: bin/gen-inventory.sh -->
|
||||
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|
||||
|
||||
<!-- END: this line ends content from: inc/after-content.default.html -->
|
||||
<!-- START: this line starts content from: inc/end-rightcolumn.default.html -->
|
||||
|
||||
</div>
|
||||
|
||||
<!-- END: this line ends content from: inc/end-rightcolumn.default.html -->
|
||||
<!-- START: this line starts content from: inc/end-row.default.html -->
|
||||
|
||||
</div>
|
||||
|
||||
<!-- END: this line ends content from: inc/end-row.default.html -->
|
||||
<!-- START: this line starts content from: inc/footer.default.html -->
|
||||
|
||||
<div class="footer">
|
||||
<hr>
|
||||
<h2>Coda</h2>
|
||||
<p><a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F2000%2Fbmeyer%2Findex.html">Nu HTML check this web page</a></p>
|
||||
<p><a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a></p>
|
||||
</div>
|
||||
|
||||
<!-- END: this line ends content from: inc/footer.default.html -->
|
||||
<!-- START: this line starts content from: inc/bottom.default.html -->
|
||||
|
||||
</body>
|
||||
</html>
|
||||
|
||||
<!-- END: this line ends content from: inc/bottom.default.html -->
|
||||
Reference in new issue
Block a user