Race The Rabbit
Race the Rabbit is a simple predator-pray game where hunters is chasing a rabbit.
In the simplest version of Race the Rabbit, the world consists of
an n x n discrete grid where each
cell is either open or, with probability p,
contains an obstacle. Assume without
loss of generality that the border cells of the world contain only obstacles.
At each time step the hunter may move north, south, east or west into an open
cell followed by the rabbit doing likewise. The rabbit moves randomly though it
will stay at its current position if it attempts to enter an obstacle cell.
There is no bound placed on the amount of computational resources the Hunter
may apply at each time step. The game ends when the hunter overtakes the
rabbit.
Rules
The world
The chance
takes place in a two-dimensional grid world which may contain obstacles in form
of holes in the ground.
- Obstacles are randomly
distributed over the world
- Only one Hunter at a time can
occupy a position in the world. Any Hunter trying to move to a position
where another hunter or an obstacle is located will simply not move and
louse its turn
Rabbit and Hunters
One Rabbit and one or two Hunters take part in Race the Rabbit.
The goal for the Hunters is to catch the rabbit by moving to the same position
as the rabbit. The Rabbit moves around randomly. Rabbit and Hunters moves in
turns with fixed order, Rabbit, Hunter 1,
Hunter 2, Rabbit and so on.
There are
two types of hunters:
Search Hunter
Has
complete information about the world, the position of the rabbit and the
position of any opponents in the game. Information is retrieved via a map that
is automatically updated as the games goes on.
Perception Hunter
Has
incomplete information about the world and positions of rabbit and opponents.
However, it can retrieve partial information via its senses. Any obstacles that
are in front of the agent or to any of its sides can be seen at a distance of 5
squares from the hunter. Obstacles behind the hunter or positioned diagonally
to the hunter is not seen. The visual field is illustrated bellow.
Exact
information about the rabbit's position can only be obtained if the rabbit are
within the visual field, similar to obstacles. However, even if the hunter can
not see the rabbit, he can still smell it and estimate an approximate position.
The quality of this approximation is better if the rabbit is near the
hunter. Formally, the smell percept
is normally distributed with a mean at the true distance to the rabbit, and a
variance of 0.1*d, where d is the Euclidian distance to the
rabbit.
The
Perception Hunter can also smell other hunters, in exactly the same way as he
can smell the rabbit.
Implementation
The game is
implemented in Java and hunters can be created as java-classes extending one of
the abstract classes SearchHunter or PerceptionHunter.
Download
Source code
for race the rabbit is available here:
Compile
Unpack the
downloaded zip-file. Open a command shell, go to the folder where the source is
stored and execute
javac *.java
Run
Execute the
following command to run Race the Rabbit
java RunRabbit <hunter1>
<hunter2> <Config.xml>
Race the
Rabbit works on any system with standard Java VM 6.0 or later. <hunter1>
and
<hunter2> should
be names of class-files implementing the Hunter interface. At least one hunter
class must be specified, but the second one is optional. As a test hunter, you
can specify ExampleHunter which comes
with the source package.
<Config.xml> is an optional argument specifying the
configuration file. If omitted, RaceTheRabbit.xml
is used and will be created if missing. This file may specify many properties
about the game, including the size of the map, where obstacles are placed,
starting positions for the rabbit and hunters, game speed and so on. The xml file
must follow racetherabbit.xsd. Another
example configuration can be found in TestMap.xml.
Documentation
See also Race the Rabbit API
Have fun!