applets/gatherers.html

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   2 <head>
   3         <title>Gatherers</title>
   4         <link rel="stylesheet" type="text/css" href="../styles.css"/>
   5 </head>
   6 <body>
   7 <div id="content">
   8 <h2>Gatherers</h2>
   9 <h3>Agent Algorithm</h3>
  10 <p>
  11         A gatherer agent chooses the closest visible piece of food
  12         that is currently not being carried by anyone (and is not
  13         already in the agent's home base) and accelerates towards it.
  14         If no "uncarried" food can be found, the agent tries to find
  15         food carried by a member of the opposing team to accelerate
  16         towards. If no food is visible the agent sets his acceleration
  17         to a random vector to search for food. When it gets close
  18         enough to pick up a piece of food, it picks it up and carries
  19         it towards its home base corner for 20 time cycles, and drops
  20         it again. The gatherer must then rest for 10 time cycles
  21         before picking up another piece of food. During these 10
  22         time cycles, the "exhausted" agent does not accelerate.
  23 </p>
  24 <h4>Pseudocode</h4>
  25 <div class="pseudocode">
  26 <pre>if have food
  27    if have carried food for 20 time cycles
  28       drop food
  29    else
  30       accelerate towards home base
  31 else if have rested for 10 time cycles
  32    if can see uncarried food not in home base
  33       if am close enough to pick it up
  34          pick up food
  35       else
  36          accelerate towards closest uncarried food
  37    else if can see food carried by opponent
  38       accelerate towards opponent with food
  39    else
  40       accelerate in random direction
  41 else
  42    set acceleration to zero</pre>
  43 </div>
  44 <h3>Observed Behavior</h3>
  45 <p>
  46         The result of this algorithm is a kind of "Capture the Flag"
  47         game, except with multiple flags (and that the flags are called
  48         "food"). The applet is set to stop play if one team wins the game
  49         by getting all the food items into its home base.
  50 </p>
  51 <p>
  52         Since one agent cannot carry a piece of food from the
  53         opponent's base without setting it down and resting for a bit, it
  54         is very likely that if an attempt is made by lone agent to steal
  55         a piece of food from the opponents' base, the food with be
  56         snatched back up by the enemy when he sets it down to rest. So,
  57         of course, the better strategy is to steal food in teams of two
  58         or more.
  59 </p>
  60 <p>
  61         If the teams have close to the same number of members, the
  62         result is pretty much a stalemate. However, if the teams are
  63         significantly unevenly matched, one will almost always win.
  64         If there are too many players on a team, they can get in
  65         the way and hinder, rather than help, efforts. Another problem
  66         that happens (especially when team sizes are high) is that agents
  67         get trapped in their own bases because they don't know to pick up
  68         a piece of food that is in their way. Since the pieces of food are
  69         defined as stationary by default, colliding with them does no good
  70         to free trapped agents. A trapped agent will only be freed if an
  71         opponent removes one of the pieces of food blocking his path.
  72 </p>
  73 <p>
  74         One unexpected observation is the benefit of the default drop
  75         spot (the place the food is placed when the agent drops it) being
  76         directly in front (in the direction of the velocity vector) of the
  77         agent. What often happens is that an agent carrying a piece of
  78         food will be pursued by one or more of his opponents. When the
  79         agent drops the food to rest, his body is between the food and the
  80         pursuers, so unless his opponents can figure a way to go around
  81         him and pick up the food within 10 time cycles, the agent can
  82         simply pick up the food again and continue!
  83 </p>
  84 <p>
  85         For added fun, try unchecking the "Stationary Food" box to allow
  86         the food to drift around and respond to collisions. The resulting
  87         behavior is that several agents from a team take on "food control
  88         duty" and stay around the home base moving food back inside that
  89         has drifted out. If the ratio of agents to food is sufficiently
  90         low, "food containment" will occupy all of their time, and there
  91         will be no missions to steal the other team's food at all!
  92 </p>
  93 <h3>The Applet</h3>
  94 <applet archive="../dist/appletbots.jar"
  95         code="appletbots.gatherers.GatherersApplet"
  96         alt="Gatherers Applet"
  97         width="600"
  98         height="450">
  99         <div>
 100                 If you see this, you need to either enable java, or install the Sun Java
 101                 Virtual Machine in your browser. To do so,
 102                 <a href="http://java.sun.com/getjava/download.html">click here</a>.
 103         </div>
 104 </applet>
 105 <h3>Source Code</h3>
 106 <ul>
 107         <li>
 108                 <a href="../src/GatherersApplet.java.html">GatherersApplet.java</a>
 109         </li>
 110         <li>
 111                 <a href="../src/Gatherer.java.html">Gatherer.java</a>
 112         </li>
 113         <li>
 114                 <a href="../src/Food.java.html">Food.java</a>
 115         </li>
 116         <li>
 117                 <a href="../src/GatherersWorld.java.html">GatherersWorld.java</a>
 118         </li>
 119 </ul>
 120 <a href="../" class="return">Back to the Applet Bots Home</a>
 121 </div>
 122 <div class="official">
 123         The official version of this file is at <a href="http://applet-bots.sourceforge.net/applets/gatherers.html">applet-bots.sourceforge.net</a>
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