Rename hint.txt and hint.text to README.md
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# Most complex ASCII fluid - Honorable mention
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Yusuke Endoh
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<mame@ruby-lang.org>
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<https://github.com/mame/>
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## Judges' comments:
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### To build:
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make endoh1
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### To run:
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./endoh1 < configuration.txt
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### Try:
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./endoh1 < endoh1.c
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./endoh1 < pour-out.txt
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./endoh1 < fountain.txt
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### Selected Judges Remarks:
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Let's play Jeopardy!
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* A: An obfuscated program that deals with complex numbers and produces animated ASCII graphics.
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* Q: What is a Mandelbrot simulator?
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Bzzzt!
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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.
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One configuration file was inspired by an [XKCD what if? entry](http://whatif.xkcd.com/6/).
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## Author's comments:
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### Synopsis
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**DO NOT FORGET "-DG=1 -DP=4 -DV=8"** and make your terminal window larger
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than 80 x 25.
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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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### What it is
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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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`-'`' `-'`-' `-'`-' `-'`' `'`' `'`' `'`'
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This program is a fluid simulator using "Smoothed-particle hydrodynamics (SPH)"
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method.
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<http://en.wikipedia.org/wiki/Smoothed-particle_hydrodynamics>
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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).
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This program reads a text from standard input, and uses it as an initial
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configuration of the particles. The character `#` 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.
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The compilation options `-DG=1 -DP=4 -DV=8` 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.
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"Marching square"-like algorithm is used to render the particles.
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<http://en.wikipedia.org/wiki/Marching_squares>
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### Portability
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The program requires a C99 compiler; it uses `complex` types and one-line
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comments. It also uses `usleep`, which may require `-D_BSD_SOURCE` 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 `-std=c99 -Wall -W -Wextra -pedantic` says
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nothing.
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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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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.
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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 `I` (complex's imaginary unit), but I bet this is cygwin's issue;
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it is surely a C99 feature.
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### Obfuscation w/ Spoiler
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First of all, the source code itself serves as an initial configuration.
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Preprocessing directives (such as `#include`)'s `#` serve as walls.
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This program uses `double complex` 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, `force += G` suffices, rather than
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`force += G*I`.
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(Incidentally, you can exert horizontal gravity by using, such as, `-DG=I`)
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Every five entries of `double complex a[]` contain information of one particle:
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position, wall-flag, density, force, and velocity, in turn.
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You can use `G`, `P`, and `V` as a guide to find the calculation code of
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gravity, pressure, and viscosity forces.
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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.
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### Notes about Additional Files
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"logo.txt" is a source of the logo in this remark file.
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"column.txt" is a water column collapse, which is a popular demo of SPH.
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"pour-out.txt" pours you a cup of tea.
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"tanada.txt" simulates "Terrace farming". ("Tanada" means a "terraced rice
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fields" in Japanese.)
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"clock.txt" is a "water" clock created by HAMANO Tsukasa.
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Other \*.txt files are due to the judges.
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"endoh1\_color.c" is a variant that shows the density by using terminal 256
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colors.
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### Acknowledgment
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I would like to thank my wife @hirekoke for her teaching me the SPH method.
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The judges <strike>ordered</strike> suggested creating a color version
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after the judgment.
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The judges and HAMANO Tsukasa (The silver medalist at this IOCCC) kindly
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provided many configuration files.
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--------------------------------------------------------------------------------
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<!--
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(c) Copyright 1984-2015, [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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