The sections have been modified a fair amount. The Entries menu has been extended to have: Fixing entries, Updating author info, Thanks for the help. The first two were moved from FAQ and the last one from About. The rationale for these, in order: entries and authors have to do with entries and most of the help involves entries. It also has to do with website but in 'about' it does not seem the right place, unless maybe it is renamed to 'Credits' or something (I am not suggesting this one way or the other). This one is debatable but that was the rationale. The Status menu has been extended to have: Markdown guidelines and Security policy. The rationale is that the markdown guidelines are part of contest guidelines and the security policy is about the status of the entries and how if there are any security problems they will not be addressed (instead of about the IOCCC). The FAQ was extended to have: Compiling entries, Running entries, How to help. The reason to not have compiling and running entries under Entries is because this is 'how to' and also the menu was too long. How to help seems like a good idea under FAQ too (was in About). About was extended to have the new 'about.html' page (from about.md). This is a rare case where a new file is useful as it fits under 'About'. The menu now is: Home page, About the IOCCC, The Judges, Contact us. I was pondering the 'About [the IOCCC]' at the top and also naming it 'About us' but it seemed like a link to index.html was necessary and as for 'about us' it seemed less clear as to whether it was about the judges or the contest itself. The FAQ has been updated slightly for this. After further inspection the bin/index.html and the inc/index.html links were removed from the about section. With these changes, renaming an item or slight reordering notwithstanding, I believe that #2006 is probably in good shape.
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width=300
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<h1>The International Obfuscated C Code Contest</h1>
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<h2>1992/vern - Best of Show</h2>
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<h3>plays chess</h3>
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</div>
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<a class="Left" href="../nathan/index.html">← 1992/nathan</a>
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<a class="Left" href="../index.html">↑ 1992 ↑</a>
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<a class="Left" href="../westley/index.html">1992/westley →</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/vern.c">C code</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/Makefile">Makefile</a>
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<a class="Right" href="#inventory">Inventory</a>
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<a class="Right" href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F1992%2Fvern%2Findex.html">✓</a>
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<h2 id="author">Author:</h2>
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<ul>
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<li>Name: <a href="../../authors.html#Vern_Paxson">Vern Paxson</a><br>
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Location: <a href="../../location.html#US">US</a> - <em>United States of America</em> (<em>United States</em>)</li>
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<h2 id="to-build">To build:</h2>
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<pre><code> make all</code></pre>
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<h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
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<p>The current status of this entry is:</p>
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<blockquote>
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<p><strong>STATUS: INABIAF - please DO NOT fix</strong></p>
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||
</blockquote>
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<p>For more detailed information see <a href="../../bugs.html#1992_vern">1992/vern in bugs.html</a>.</p>
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<h2 id="to-use">To use:</h2>
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<pre><code> ./vern 3 # <-- default is 2</code></pre>
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<h2 id="try">Try:</h2>
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<p>You might start off by giving the following input:</p>
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<pre><code> 63 43
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76 55
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71 52
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67 57 # <-- this may take a while</code></pre>
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<h2 id="judges-remarks">Judges’ remarks:</h2>
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<p>The judges assume no responsibility for the obfuscated opening
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suggested above. :-)</p>
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<p>For a real quick game try:</p>
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<pre><code> ./vern
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65 55
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66 46</code></pre>
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<p><strong>NOTE</strong>: Move values must be restricted to the range 00 to 77.</p>
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<p><strong>NOTE</strong>: Because some mailers have problems with the original winning source,
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a slightly modified version with shorter lines has been provided.</p>
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<h2 id="authors-remarks">Author’s remarks:</h2>
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<p>This program plays chess. You play the white pieces and the program the black
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pieces. Moves are entered as a two-digit number specifying the coordinates of
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the piece to be moved followed by another two-digit number specifying the
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coordinates of where to move it. Rows and columns are numbered starting with
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<code>(0,0)</code> for the upper-left-hand corner (black’s queen’s rook) and going to
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<code>(7,7)</code> for the lower-right-hand corner (white’s king’s rook). For example, the
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<code>PK4</code> opening for white is indicated as <code>"64 44" (without the quotes)</code>. Moves
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are read using <code>scanf()</code> so care should be taken to not enter the wrong number
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of fields.</p>
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<p>If the move you enter is illegal then you are just prompted again to
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move. If the move is legal then the new position is displayed and the
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program starts computing its response. For every 64 board positions it
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examines a “.” is printed. Once it has chosen its move it simply
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displays the board updated to reflect the move.</p>
|
||
<p>Your move is prompted for using a string like <code>"1351 9 2 >"</code>. The first
|
||
number is how many board positions the program examined when computing
|
||
its previous response. The second number is its anticipated value for
|
||
the move it just made (with larger numbers meaning an ultimately better
|
||
board position for it), and the third number is the evaluation it
|
||
assigns to the your current position (larger numbers meaning better
|
||
positions for you). A <code>></code> indicates that you are not in check; for
|
||
check it is changed to <code>!</code>.</p>
|
||
<p>There are a few limitations on play:</p>
|
||
<ul>
|
||
<li>castling can only be done on the king’s side.</li>
|
||
<li>prohibitions against castling out of or through check are not enforced.</li>
|
||
<li>prohibitions against castling if the king or rook have moved are not enforced.</li>
|
||
<li>pawns are always promoted to queens.</li>
|
||
<li>en passant is not allowed.</li>
|
||
<li>the board-position-repeated-three-times and fifty-moves stalemates are not
|
||
recognized.</li>
|
||
</ul>
|
||
<p>If you checkmate the computer it prints “Rats!” and exits. If your own
|
||
checkmate is imminent it prints “Har har.” but doesn’t exit so it can
|
||
rub your nose in defeat (which may be a move or two away if you’re
|
||
playing at a high “ply” - see the next paragraph). Stalemates are not
|
||
recognized per se, but when selecting its move the program assigns a
|
||
stalemate position a value of 0 so it will try for a stalemate if its
|
||
other options are worse.</p>
|
||
<p>The program takes one optional argument indicating the ply (lookahead) it should
|
||
use. The default is 2, which is enough to keep it from making flaming blunders.
|
||
The higher the ply, the better the play, and the longer you have to wait. For
|
||
example, at a ply of 2, a response to the <code>PK4</code> opening takes about 1.8 CPU
|
||
seconds on a SPARC ELC when compiled <code>-O</code> with Sun <code>cc</code>. A ply of 3 takes 13
|
||
CPU seconds (and results in a different response to <code>PK4</code>) and a ply of 4 takes
|
||
a little under 4 CPU minutes (and for <code>PK4</code> comes up with the same response as a
|
||
ply of 3). A ply of 3 is in general good enough to avoid not only flaming
|
||
blunders but also immediately stupid moves altogether. A ply of 4 will find all
|
||
mate-in-two’s.</p>
|
||
<h3 id="notice-to-those-who-wish-for-a-greater-challenge">NOTICE to those who wish for a greater challenge:</h3>
|
||
<p><strong>If you want a greater challenge, don’t read any further</strong>:
|
||
just try to understand the program via the source.</p>
|
||
<p>If you get stuck, come back and read below for additional hints and information.</p>
|
||
<h3 id="obfuscation">Obfuscation</h3>
|
||
<p>This program is obfuscated in a number of ways. First, it abuses the
|
||
contest rule regarding <code>;</code>, <code>{</code>, and <code>}</code> in the source not counting
|
||
against the non-whitespace character limit if followed by whitespace.
|
||
As can be seen from the build file, certain combinations of these
|
||
characters followed by a particular whitespace character are expanded
|
||
at build time into much-needed text. Without this hack the program
|
||
wouldn’t pass the character limit. A nice side effect is that the
|
||
initial source is gloriously difficult to peruse. In particular, the Makefile
|
||
does:</p>
|
||
<pre><code> sed <vern.c 's/{ /(/g;s/} /)/g;s/; /#define /' |
|
||
sed 's/} /=/g;s/{ /i/g' >vern.tmp.c</code></pre>
|
||
<p>and compiles <code>vern.tmp.c</code>.</p>
|
||
<p>Second, the rather ho-hum step has been taking of naming each variable
|
||
with a one or two letter identifier to render it meaningless (and save
|
||
space). This tactic is rather effective in a complex program.</p>
|
||
<p>Third, the board is represented not as an array of pieces but rather as
|
||
an array of function pointers (with a separate array representing
|
||
whether a piece is white or black). This obfuscates the program’s
|
||
central data structure. There is one function per type of piece; when
|
||
called they return 1 if the current move is illegal for that piece and
|
||
0 if it is legal. The functions also as a side effect set a global
|
||
indicating the type of the piece (though the type can also be determined
|
||
by comparing the function pointer with the function itself).</p>
|
||
<p>Fourth, there are no independent routines for generating potential moves.
|
||
Instead, the program generates its moves by brute force: for every piece it
|
||
controls on the board, it attempts to move it to every square on the board.
|
||
Those moves that are legal it then explores to see their effects, using
|
||
<a href="https://en.wikipedia.org/wiki/Alpha-beta_pruning">alpha-beta search</a>. This
|
||
tactic somewhat obfuscates the algorithm used by the program.</p>
|
||
<p>Finally, there are three key constants that occur throughout the program: <code>64</code>,
|
||
<code>8</code>, and <code>3</code> (<code>lg 8</code>). Rather than making these available at compile-time,
|
||
which provides a hint as to what the program is up to, they are computed
|
||
probabilistically at run-time. An instance of the <a href="https://en.wikipedia.org/wiki/Renewal_theory#Inspection_paradox">“Inspection
|
||
Paradox”</a> is
|
||
used which happens to produce a value that on average is close to <code>64</code>.</p>
|
||
<p><code>10000</code> instances of this value are computed, added up, and then divided by
|
||
<code>100</code>. Sometimes the value produced will be <code>63</code> or <code>65</code> instead of <code>64</code> (but
|
||
I’ve never observed any other values), so the result is then rounded to the
|
||
nearest multiple of <code>4</code>, and then the other constants are derived from it.</p>
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
||
|
||
For more information, see:
|
||
|
||
https://creativecommons.org/licenses/by-sa/4.0/
|
||
|
||
-->
|
||
<!-- AFTER: last line of markdown file: 1992/vern/README.md -->
|
||
|
||
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|
||
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|
||
|
||
<!-- START: this line starts content generated by: bin/output-index-inventory.sh -->
|
||
|
||
<div id="inventory">
|
||
<h1 id="inventory-for-1992vern">Inventory for 1992/vern</h1>
|
||
</div>
|
||
<h2 id="primary-files">Primary files</h2>
|
||
<ul>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/vern.c">vern.c</a> - entry source code</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/Makefile">Makefile</a> - entry Makefile</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/vern.orig.c">vern.orig.c</a> - original source code</li>
|
||
</ul>
|
||
<h2 id="secondary-files">Secondary files</h2>
|
||
<ul>
|
||
<li><a href="1992_vern.tar.bz2">1992_vern.tar.bz2</a> - download entry tarball</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/README.md">README.md</a> - markdown source for this web page</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/.entry.json">.entry.json</a> - entry summary and manifest in JSON</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
|
||
<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1992/vern/.path">.path</a> - directory path from top level directory</li>
|
||
<li><a href="index.html">index.html</a> - this web page</li>
|
||
</ul>
|
||
<hr style="width:10%;text-align:left;margin-left:0">
|
||
<h4>
|
||
Jump to: <a href="#">top</a>
|
||
</h4>
|
||
|
||
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||
|
||
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||
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||
|
||
</div>
|
||
|
||
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|
||
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|
||
|
||
<!--
|
||
|
||
Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
|
||
|
||
You are free to share and adapt this file under the terms of this license:
|
||
|
||
Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
|
||
|
||
For more information, see:
|
||
|
||
https://creativecommons.org/licenses/by-sa/4.0/
|
||
|
||
-->
|
||
|
||
<div class="footer">
|
||
|
||
<div id="copyright"><h3>Copyright © 1984-2024 by Landon Curt Noll:
|
||
<a href="https://creativecommons.org/faq/#what-does-some-rights-reserved-mean"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">Some Rights Reserved</a></h3>
|
||
<p>
|
||
This work is <b>licensed by Landon Curt Noll</b> under
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/?ref=chooser-v1"
|
||
target="_blank"
|
||
rel="license noopener noreferrer"
|
||
style="display:inline-block;">CC BY-SA 4.0</a></b>.
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/cc.png"
|
||
alt="cc inside circle symbol">
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/by.png"
|
||
alt="person inside circle symbol">
|
||
<img style="height:22px!important;margin-left:3px;vertical-align:text-bottom;"
|
||
src="../../png/sa.png"
|
||
alt="arrow looping back on itself inside circle symbol"><br>
|
||
You should <b>carefully review</b> the
|
||
<b><a href="https://creativecommons.org/licenses/by-sa/4.0/legalcode.en"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">CC BY-SA 4.0 LEGAL CODE</a></b>
|
||
before using the licensed material.<br>
|
||
You may wish to review the
|
||
<b><a href="../../license.html"
|
||
target="_blank"
|
||
rel="license noopener noreferrer">highlights of some of the key features and terms</a></b>
|
||
of <b>CC BY-SA 4.0</b>.<br>
|
||
</p>
|
||
</div>
|
||
|
||
<div id="coda"><h3>Coda</h3>
|
||
<p>
|
||
<a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F1992%2Fvern%2Findex.html" rel="nofollow">Nu HTML check this web page</a><br>
|
||
<a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a><br>
|
||
</p>
|
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</body>
|
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</html>
|
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