mirror of https://github.com/dirtbags/tanks.git
118 lines
4.9 KiB
HTML
118 lines
4.9 KiB
HTML
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<!DOCTYPE html>
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<html lang="en-US">
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<head>
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<meta charset='utf-8'>
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<meta name="viewport" content="width=device-width">
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<link rel="stylesheet" href="/assets/css/dirtbags.css?v=">
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<link rel="icon" type="image/png" href="/assets/images/icon.png">
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<script src="assets/js/tanks.js"></script>
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<script src="assets/js/figures.js"></script>
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<title> by </title>
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</head>
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<body>
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<h1 id="title">History</h1>
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<p>This is a port of the “Tanks” program written by Paul Ferrell
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<a href="mailto:pflarr@clanspum.net">pflarr@clanspum.net</a> in 2009-2010. Paul created the entire game based
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off a brief description I provided him of
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<a href="http://tpoindex.github.io/crobots">Crobots</a>
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and a vague desire to
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“make something fun for high school kids to learn some programming.” We
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ran Paul’s Tanks as part of a 100-attendee computer security contest in
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February of 2010 and by all accounts it was a huge success. It even
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made the nightly news.</p>
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<p>Paul’s version was written in Python and provided a custom language
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called “Bullet”, which looked like this:</p>
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<div class="highlighter-rouge"><pre class="highlight"><code>>addsensor(50, 0, 5, 1); # 0
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>addsensor(100, 90, 150, 1); # 1
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>addsensor(100, 270, 150, 1); # 2
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>addsensor(100, 0, 359, 0); # 3
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# Default movement if nothing is detected
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: move(70, 70) . turretccw();
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random(2, 3): move(40, 70) . turretccw();
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random(1, 3): move(70, 40) . turretccw();
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# We found something!!
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sense(3): move(0, 0);
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sense(1): turretcw();
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sense(2): turretccw();
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sense(0): fire();
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</code></pre>
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</div>
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<table class="figure">
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<caption>"Chashtank" cleans up.</caption>
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<tr>
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<td>
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<canvas id="shortround"></canvas>
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<script type="application/javascript">
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start("shortround", shortround);
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</script>
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</td>
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</tr>
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</table>
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<p>Nick Moffitt played with this original version and convinced me (Neale)
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that something like Forth would be a better language. I added some code
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to accept a scaled-down version of PostScript. The IRC channel we
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frequent collectively agreed to give this new language the derisive name
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“Forf”, which should ideally be followed by punching someone after it is
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spoken aloud. I wrote a Python implementation of Forf, which was slow,
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and then Adam Glasgall wrote a C implementation, which was quick.</p>
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<p>I decided to take Tanks to Def Con in July 2010, and just for bragging
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rights, to have it run on an Asus WL-500gU. This is a $50 device with a
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240 MHz MIPS CPU, 16MB RAM, and a 4MB flash disk, along with an
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802.11b/g radio, 4-port 10/100 switch, and an additional 10/100 “uplink”
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port; it’s sold as a home wireless router. I had originally intended to
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run it off a lantern battery just for fun, but eventually thought better
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of it: doing so would be wasteful for no good reason.</p>
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<p>Aaron McPhall <a href="mailto:amcphall@mcphall.org">amcphall@mcphall.org</a>, my summer intern at the time, got
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OpenWRT and Python onto the box and benchmarked it at about 60 seconds
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for a 16-tank game, after he had profiled the code and optimized a lot
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of the math. That wasn’t bad, it meant we could run a reasonably-sized
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game at one turn per minute, which we knew from past experience was
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about the right rate. But it required a USB thumb drive to hold Python,
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and when we used the Python Forf implementation, the run-time shot up to
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several minutes. I began this C port while Adam Glasgall, another fool
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on the previously-mentioned IRC channel, started work on a C version of
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a Forf interpreter.</p>
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<p>This C version with Forf runs about 6 times faster than the Python
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version with Bullet, on the WL-500gU. A 1GHz Intel Atom runs a 16-tank
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game in about 0.2 seconds.</p>
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<h2 id="whats-so-great-about-forf">What’s so great about Forf?</h2>
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<p>Nothing’s great about Forf. It’s a crummy language that only does
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integer math. For this application it’s a good choice, for the
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following reasons:</p>
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<ul>
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<li>No library dependencies, not even malloc</li>
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<li>Runs in fixed size memory</li>
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<li>Not Turing-complete, I think (impossible to make endless loops)</li>
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<li>Lends itself to genetic algorithms</li>
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</ul>
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<nav>
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<ul>
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<li><a href="/">Home</a></li>
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<li><a href="/running">Running</a></li>
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<li><a href="/history">History</a></li>
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<li><a href="/thanks">Thanks</a></li>
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<li><a href="https://github.com/dirtbags/tanks" title="Tanks on Github">Source</a></li>
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</ul>
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</nav>
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</body>
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</html>
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