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212 lines
8.5 KiB
HTML
212 lines
8.5 KiB
HTML
11 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta name="GENERATOR" content="mkd2html 2.1.5a DL=DISCOUNT">
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
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<link rel="stylesheet"
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type="text/css"
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href="hint.css">
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<title>Most complex ASCII fluid - Honorable mention</title>
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</head>
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<body>
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<h1>Most complex ASCII fluid - Honorable mention</h1>
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<p>Yusuke Endoh<br>
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<a href="mailto:mame@tsg.ne.jp">mame@tsg.ne.jp</a></p>
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<h2>Judges' comments:</h2>
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<h3>To build:</h3>
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<pre><code>make endoh1
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</code></pre>
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<h3>To run:</h3>
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<pre><code>./endoh1 < configuration.txt
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</code></pre>
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<h3>Try:</h3>
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<pre><code>./endoh1 < endoh1.c
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./endoh1 < pour-out.txt
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./endoh1 < fountain.txt
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</code></pre>
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<h3>Selected Judges Remarks:</h3>
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<p>Let’s play Jeopardy!</p>
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<ul>
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<li>A: An obfuscated program that deals with complex numbers and produces animated ASCII graphics.</li>
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<li>Q: What is a Mandelbrot simulator?</li>
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</ul>
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<p>Bzzzt!</p>
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<p>Such heavily squeezed fluid simulation (this is parsed uniquely
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as fluids are not squeezable) has a few quirks that the judges were
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happy to experiment with.</p>
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<p>One configuration file was inspired by an <a href="http://whatif.xkcd.com/6/">XKCD what if? entry</a>.</p>
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<h2>Author’s comments:</h2>
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<h3>Synopsis</h3>
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<p><strong>DO NOT FORGET “-DG=1 -DP=4 -DV=8”</strong> and make your terminal window larger
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than 80 x 25.</p>
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<pre><code>gcc endoh1.c -DG=1 -DP=4 -DV=8 -D_BSD_SOURCE -o endoh1 -lm
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./endoh1 < endoh1.c
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./endoh1 < logo.txt
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./endoh1 < column.txt
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./endoh1 < pour-out.txt
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./endoh1 < tanada.txt
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</code></pre>
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<h3>What it is</h3>
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<pre><code>,___. ,. ,. ,. ,___. ,. ,. ,.
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|/--' || `' || |/--' `' || |\_.
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|\__. || ,. ,. ,. ,__/| |\__. ,. ,____. ,. ,. || ,_. |/-' ,_. ,__.
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|/--' || || || || |/-\| `--\| || |/\/\| || || || ,/-\. || ,/-\. |/-\.
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|| || `\_/| || |\_/| ,__/| || |||||| `\_/| || `\_/\.`\_. `\_/' || `'
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`' `' `--' `' `---' `---' `' `'`'`' `--' `' `-'`' `-' `-' `'
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,.,. ,.,.
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,/\/\. ,. ,. ,. ,/\/\. ,. ,. ,__.
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|||#/' || `' ,_.|| |||#/' `',_.,__. || ||\\. ,.
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|||#\. || ,. ,. ,.,/#||| |\//\. ,.|#||##| ,. ,. || ,.,. |\/-' ,.,. ,.|\.
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|\/--' ||,/\.|| |||#/\/| `\#||| |||#||/\|,/\.|| ||,/'`\.|#| ,/'`\.|\/-\.
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`\| ||`\#||| |||#||\| ,//\/| ||`\|||||`\#||| ||`\.,/\/\|,.`\.,/'`\| `'
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`' `' `-'`' `'`-'`-' `-'`-' `' `'`'`' `-'`' `' `'`--'`'`' `'`' `'
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,_.,_. ,. ,. ,. ,_.,_. ,. ,. ,.
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|#||#| || `' || |#||#| `' || ||,_.
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||\/#| ||,. ,. ,.,_.,/| |\||#| ,.,_.,__.,. ,. || ,.,. |||#| ,.,. ,.,_.
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|||##| |||| || |||#||#| |#||#| |||#||##||| || ||,/||\.||`-',/||\.|||#\.
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||`--' ||`\_.|| |||\||#| |#||#| ||||'||\|`\_.|| ||`\||#|`\.,.`\||/'||`--'
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`' `' |#||| `'|#||#| |#||#| `'`' `'`' |#||| `' |||/' |||| |||| `'
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`-'`' `-'`-' `-'`-' `-'`' `'`' `'`' `'`'
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</code></pre>
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<p>This program is a fluid simulator using “Smoothed-particle hydrodynamics (SPH)”
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method.</p>
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<p><a href="http://en.wikipedia.org/wiki/Smoothed-particle_hydrodynamics">http://en.wikipedia.org/wiki/Smoothed-particle_hydrodynamics</a></p>
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<p>The SPH particles represent the fluid flow. Particles have information about
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the position, density, and velocity. In every simulation step, they are
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changed by pressure force, viscosity force, and external force (i.e., gravity).</p>
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<p>This program reads a text from standard input, and uses it as an initial
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configuration of the particles. The character <code>#</code> represents “wall particle” (a
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particle with fixed position), and any other non-space characters represent
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free particles.</p>
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<p>The compilation options <code>-DG=1 -DP=4 -DV=8</code> represent, respectively, the factor
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of gravity, pressure, and viscosity. By changing their values, you can see
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different fluid behavior.</p>
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<p>“Marching square”-like algorithm is used to render the particles.</p>
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<p><a href="http://en.wikipedia.org/wiki/Marching_squares">http://en.wikipedia.org/wiki/Marching_squares</a></p>
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<h3>Portability</h3>
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<p>The program requires a C99 compiler; it uses <code>complex</code> types and one-line
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comments. It also uses <code>usleep</code>, which may require <code>-D_BSD_SOURCE</code> or somewhat
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to build with no warning. Under these conditions, it should be portable.
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At least, recent compilers with <code>-std=c99 -Wall -W -Wextra -pedantic</code> says
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nothing.</p>
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<pre><code>gcc -DG=1 -DP=4 -DV=8 -D_BSD_SOURCE -std=c99 -Wall -W -Wextra -pedantic endoh1.c
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clang -DG=1 -DP=4 -DV=8 -D_BSD_SOURCE -std=c99 -Wall -W -Wextra -pedantic endoh1.c
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</code></pre>
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<p>I expect it to work in any Unix-like environment. VTxxx/ANSI sequences are
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used to clear screen and move cursor to home.</p>
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<p>I’ve tested with gcc-4.6.3 and clang-3.0 on Linux (Ubuntu 12.04)
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and gcc-4.5.3 and clang-3.1 on Cygwin. On Cygwin, gcc and clang complain about
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a usage of <code>I</code> (complex’s imaginary unit), but I bet this is cygwin’s issue;
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it is surely a C99 feature.</p>
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<h3>Obfuscation w/ Spoiler</h3>
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<p>First of all, the source code itself serves as an initial configuration.
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Preprocessing directives (such as <code>#include</code>)’s <code>#</code> serve as walls.</p>
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<p>This program uses <code>double complex</code> to represent any 2D vector. But, note that
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x-axis and y-axis is swapped (real axis = y-axis, imaginary axis = x-axis).
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The purpose of swapping is not only obfuscation, but also short coding: for
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example, to add gravity to total force, <code>force += G</code> suffices, rather than
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<code>force += G*I</code>.
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(Incidentally, you can exert horizontal gravity by using, such as, <code>-DG=I</code>)</p>
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<p>Every five entries of <code>double complex a[]</code> contain information of one particle:
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position, wall-flag, density, force, and velocity, in turn.</p>
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<p>You can use <code>G</code>, <code>P</code>, and <code>V</code> as a guide to find the calculation code of
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gravity, pressure, and viscosity forces.</p>
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<p>Though some assignments may look meaningless, it is actually meaningful; it
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extracts “integer part of real part” from a complex value by assigning (and
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casting) it to an integer-type variable.</p>
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<h3>Notes about Additional Files</h3>
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<p>“logo.txt” is a source of the logo in this remark file.</p>
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<p>“column.txt” is a water column collapse, which is a popular demo of SPH.</p>
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<p>“pour-out.txt” pours you a cup of tea.</p>
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<p>“tanada.txt” simulates “Terrace farming”. (“Tanada” means a “terraced rice
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fields” in Japanese.)</p>
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<p>“clock.txt” is a “water” clock created by HAMANO Tsukasa.</p>
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<p>Other *.txt files are due to the judges.</p>
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<p>“endoh1_color.c” is a variant that shows the density by using terminal 256
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colors.</p>
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<h3>Acknowledgment</h3>
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<p>I would like to thank my wife @hirekoke for her teaching me the SPH method.</p>
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<p>The judges <strike>ordered</strike> suggested creating a color version
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after the judgment.</p>
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<p>The judges and HAMANO Tsukasa (The silver medalist at this IOCCC) kindly
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provided many configuration files.</p>
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<hr />
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<!--
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(c) Copyright 1984-2012, [Leo Broukhis, Simon Cooper, Landon Curt Noll][judges] - All rights reserved
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This work is licensed under a [Creative Commons Attribution-ShareAlike 3.0 Unported License][cc].
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[judges]: http://www.ioccc.org/judges.html
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[cc]: http://creativecommons.org/licenses/by-sa/3.0/
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-->
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<TABLE><TR>
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<TD><a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-sa/3.0/88x31.png" /></a></TD>
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<TD><P>© Copyright 1984-2012,
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<A HREF="/judges.html">Leo Broukhis, Simon Cooper, Landon Curt Noll</A>
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- All rights reserved<BR>
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This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 Unported License</a>.</P></TD>
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<TD> <!--<a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Transitional" height="31" width="88"></a>--></TD>
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</TR></TABLE>
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</body>
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</html>
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