Landon Curt Noll
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<img src="../../png/ioccc.png" alt="IOCCC image by Matt Zucker" width=300 height=110>
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<h1>The International Obfuscated C Code Contest</h1>
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<h2>2015/hou - Most Well-rounded Hash</h2>
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<div class="navbar">
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<a class="Left" href="../endoh4/index.html">← endoh4</a>
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<a class="Left" href="../index.html">↑ 2015 ↑</a>
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<a class="Left" href="../howe/index.html">howe →</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/prog.c">C code</a>
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<a class="Right" href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/Makefile">Makefile</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#Qiming_HOU">Qiming HOU</a><br>
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Location: <a href="../../location.html#CN">CN</a> - <em>People’s Republic of China</em> (<em>China</em>)</li>
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<h2 id="to-build">To build:</h2>
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<pre><code> make</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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<pre><code> STATUS: INABIAF - please **DO NOT** fix</code></pre>
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<p>For more detailed information see <a href="../../bugs.html#2015_hou">2015 hou bugs</a>.</p>
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<h2 id="to-use">To use:</h2>
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<pre><code> echo something | ./prog
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./prog < file</code></pre>
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<h2 id="try">Try:</h2>
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<pre><code> ./try.sh</code></pre>
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<h2 id="judges-remarks">Judges’ remarks:</h2>
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<p>A good start for understanding this entry might be
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<a href="rfc1321.txt">rfc1321.txt</a>. How does it compute this using only a
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single looping construct? The original reference source code for this
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algorithm is about 355 lines of code, yet this entry is only 199 lines with
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one statement per line and it isn’t using lots of macro expansion tricks like
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the reference code!</p>
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<p>Some things that make you go, “huh?”</p>
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<pre><code> ./prog < prog.c | cut -c-5
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./prog < Makefile | cut -c-4</code></pre>
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<p>How are those values magically returned?</p>
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<p>What happens with a large file? Something over 256K.</p>
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<pre><code> ./prog < large_file</code></pre>
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<p>Where does that message come from?</p>
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<h2 id="authors-remarks">Author’s remarks:</h2>
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<p>This looks like a normal C program.</p>
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<p>Almost everything is a <code>double</code>.</p>
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<p>There are tell-tale signs like <code>pow(2,(?/12))</code> and <code>exp(-?*?)</code> (names redacted).
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You can also find a bunch of cosines and polynomial evaluations.</p>
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<p>It looks like a ????? ???????????, right?</p>
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<p>Run and find out.</p>
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<h3 id="why-obfuscated">Why obfuscated</h3>
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<p>Some poor scripting folks only have access to doubles (Jav?script, L?a, BA?IC,
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etc.).</p>
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<p>As a C programmer, I feel obliged to show a gesture of sympathy, to experience
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their pain and provide an answer.</p>
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<p>Except when absolutely necessary (<code>printf</code>, <code>int main()</code>, array indexing), there
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isn’t a single integer. Even <code>getchar()</code> and <code>EOF</code> are immediately converted.</p>
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<p>Since <code>bool</code> counts as an integer type too, there is no boolean either. No
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comparison, no <code>if</code>, no <code>?:</code>, no <code>||</code> <code>&&</code>. Everything is done in a single loop
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that terminates on <code>printf(3)</code>. Straight up arithmetic.</p>
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<p><code>floor(3)</code> and <code>ceil(3)</code> are technically double-to-double functions, but they feel
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like cheating. Yes <code>cos(3)</code>, no <code>floor(3)</code>.</p>
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<h3 id="limitations">Limitations</h3>
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<p>Hard requirements:</p>
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<ul>
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<li><p>The platform must implement the <code>double</code> type as IEEE754-compliant 64-bit
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floating point numbers. The 80-bit intermediate format used by x87 is
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considered as an violation of this. The code should print an error message on
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such platforms.</p></li>
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<li><p>The program must start with the CPU / FPU in round-to-nearest mode.</p></li>
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</ul>
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<p>Soft requirements:</p>
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<ul>
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<li><p>The compiler must respect <code>volatile</code>. The code is formatted to warn about
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that, though.</p></li>
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<li><p>The printed result is only correct on little-endian machines. The program
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takes care to warn about this issue after printing an incorrect big-endian
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result. Error messages become garbled, though.</p></li>
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</ul>
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<p>Tested platforms:</p>
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<ul>
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<li>Linux 3.18.7, Rasperberry Pi 2, clang 3.0-6.2, (works)</li>
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<li>Linux 3.18.7, Rasperberry Pi 2, gcc 4.6.3, (works)</li>
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<li>Mac OS X 10, x64, Apple LLVM version 6.1.0 (clang-602.0.53), (works)</li>
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<li>Windows 8.1, x86, MSVC 2012 (works)</li>
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<li>Windows 8.1, x64, MSVC 2012 (works)</li>
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<li>Windows 8.1, x86, MinGW gcc 4.6.2 (fails, prints error message)</li>
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<li>Windows 8.1, x86, MinGW gcc 4.6.2 with -msse2 -mfpmath=sse (works)</li>
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</ul>
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<!--
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Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
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You are free to share and adapt this file under the terms of this license:
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Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
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For more information, see:
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<div id="inventory">
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<h1 id="inventory-for-2015hou">Inventory for 2015/hou</h1>
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</div>
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<h2 id="primary-files">Primary files</h2>
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<ul>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/prog.c">prog.c</a> - entry source</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/Makefile">Makefile</a> - entry Makefile</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/prog.orig.c">prog.orig.c</a> - original source</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/try.sh">try.sh</a> - how to run</li>
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<li><a href="rfc1321.txt">rfc1321.txt</a> - RFC 1321 - MD5 Message-Digest Algorithm</li>
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</ul>
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<h2 id="secondary-files">Secondary files</h2>
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<ul>
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<li><a href="2015_hou.tar.bz2">2015_hou.tar.bz2</a> - download entry tarball</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/README.md">README.md</a> - markdown source for this web page</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/.entry.json">.entry.json</a> - description of entry in JSON</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/.gitignore">.gitignore</a> - list of files that should not be committed under git</li>
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<li><a href="large">large</a> - large input data</li>
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<li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2015/hou/.path">.path</a> - directory path from top directory</li>
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<li><a href="index.html">index.html</a> - this web page</li>
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</ul>
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<hr style="width:10%;text-align:left;margin-left:0">
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<h4>
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Jump to: <a href="#">top</a>
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<!--
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Copyright © 1984-2024 by Landon Curt Noll. All Rights Reserved.
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You are free to share and adapt this file under the terms of this license:
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Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
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For more information, see:
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<div id="copyright"><h2>Copyright and CC BY-SA 4.0 License</h2></div>
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<p>All IOCCC content including this file and web page are:</p>
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<b> Copyright © 1984-2024 by Landon Curt Noll. <a href="https://creativecommons.org/faq/#what-does-some-rights-reserved-mean">Some Rights Reserved</a>.</b>
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<p>This work is licensed by Landon Curt Noll under:</p>
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<p><b><a href="https://creativecommons.org/licenses/by-sa/4.0/?ref=chooser-v1"
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target="_blank" rel="license noopener noreferrer" style="display:inline-block;"> CC BY-SA 4.0
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<p>The <b>CC BY-SA 4.0 LEGAL CODE</b> for this license is found under:</p>
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<h2>Coda</h2>
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<p><a href="https://validator.w3.org/nu/?doc=https%3A%2F%2Fioccc-src.github.io%2Ftemp-test-ioccc%2F2015%2Fhou%2Findex.html">Nu HTML check this web page</a></p>
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<p><a href="#top">Jump to top</a> <a href="#content">Jump to Content</a> <a href="#inventory">Jump to Inventory</a></p>
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