Extra Credit: Pacman Capture the Flag

Introduction

The course contest involves a multi-player capture-the-flag variant of Pacman, where agents control both Pacman and ghosts in coordinated team-based strategies. Your team will try to eat the food on the far side of the map, while defending the food on your home side. The contest code is available as a zip archive. It should be run in the same Python environemnt as previous assignments.

Key Files to Read:

• capture.py The main file that runs games locally. This file also describes the new capture the flag GameState type and rules.

• captureAgents.py Specification and helper methods for capture agents.

• baselineTeam.py Example code that defines two very basic reflex agents, to help you get started.

Files to Edit:

• myTeam.py This is where you define your own agents for inclusion in the competition. (This is the only file that you submit.)

Supporting Files (Do not Modify):

• game.py The logic behind how the Pacman world works. This file describes several supporting types like AgentState, Agent, Direction, and Grid.

• util.py Useful data structures for implementing search algorithms.

• distanceCalculator.py Computes shortest paths between all maze positions.

• graphicsDisplay.py Graphics for Pacman

• graphicsUtils.py Support for Pacman graphics

• textDisplay.py ASCII graphics for Pacman

• keyboardAgents.py Keyboard interfaces to control Pacman

• layout.py Code for reading layout files and storing their contents

Rules of Pacman Capture the Flag

Layout

The Pacman map is now divided into two halves: blue (right) and red (left). Red agents (which all have even indices) must defend the red food while trying to eat the blue food. When on the red side, a red agent is a ghost. When crossing into enemy territory, the agent becomes a Pacman.

Scoring

As a Pacman eats food dots, those food dots are stored up inside of that Pacman and removed from the board. When a Pacman returns to his side of the board, he "deposits" the food dots he is carrying, earning one point per food pellet delivered. Red team scores are positive, while Blue team scores are negative.

If Pacman is eaten by a ghost before reaching his own side of the board, he will explode into a cloud of food dots that will be deposited back onto the board.

Eating Pacman

When a Pacman is eaten by an opposing ghost, the Pacman returns to its starting position (as a ghost). No points are awarded for eating an opponent.

Power Capsules

If Pacman eats a power capsule, agents on the opposing team become "scared" for the next 40 moves, or until they are eaten and respawn, whichever comes sooner. Agents that are "scared" are susceptible while in the form of ghosts (i.e., while on their own team's side) to being eaten by Pacman. Specifically, if Pacman collides with a "scared" ghost, Pacman is unaffected, and the ghost respawns at its starting position (no longer in the "scared" state).

Observations

Agents can only observe an opponent's exact configuration (position and direction) if they or their teammate is within 5 squares (Manhattan distance). In addition, an agent always gets a noisy distance reading for each agent on the board, which can be used to approximately locate unobserved opponents.

Winning

A game ends when one team returns all but two of the opponents' dots. Games are also limited to 1200 agent moves (300 moves per each of the four agents). If this move limit is reached, whichever team has returned the most food wins. If the score is zero (i.e., tied) this is recorded as a tie game.

Computation Time

We will run your submissions on a CSE server. Each agent has 3 second to return each action. Each move which does not return within one second will incur a warning. After three warnings, or any single move taking more than 5 seconds, the game is forfeit. There will be an initial start-up allowance of 15 seconds (use the registerInitialState function). If your agent times out or otherwise throws an exception, an error message will be present in the log files, which you can download from the results page.

Designing Agents

Unlike earlier projects, an agent now has the more complex job of trading off offense versus defense and effectively functioning as both a ghost and a Pacman in a team setting. Furthermore, the limited information provided to your agent makes things more difficult.

Baseline Team

To kickstart your agent design, we have provided you with a team of two baseline agents, defined in baselineTeam.py. They are quite bad. The OffensiveReflexAgent simply moves toward the closest food on the opposing side. The DefensiveReflexAgent wanders around on its own side and tries to chase down invaders it happens to see.

File Format

You should include your agents in a file of the same format as myTeam.py. Your agents must be completely contained in this file.  

Interface

The GameState in capture.py should look familiar, but contains new methods like getRedFood, which gets a grid of food on the red side (note that the grid is the size of the board, but is only true for cells on the red side with food). Also, note that you can list a team's indices with getRedTeamIndices, or test membership with isOnRedTeam.

Finally, you can access the list of noisy distance observations via getAgentDistances. These distances are within 6 of the truth, and the noise is chosen uniformly at random from the range [-6, 6] (e.g., if the true distance is 6, then each of {0, 1, ..., 12} is chosen with probability 1/13). You can get the likelihood of a noisy reading using getDistanceProb.

Distance Calculation

To facilitate agent development, we provide code in distanceCalculator.py to supply shortest path maze distances.

CaptureAgent Methods

To get started designing your own agent, we recommend subclassing the CaptureAgent class. This provides access to several convenient methods, such as:

getFood(self, gameState)

Returns the food you're meant to eat. This is in the form of a matrix where m[x][y]=True if there is food you can eat (based on your team) in that square.

getFoodYouAreDefending(self, gameState)

Returns the food you're meant to protect (i.e., that your opponent is supposed to eat). This is in the form of a matrix where m[x][y]=True if there is food at (x,y) that your opponent can eat.

getOpponents(self, gameState)

Returns agent indices of your opponents. This is the list of the numbers of the agents (e.g., red might be [1,3]).

getTeam(self, gameState)

Returns agent indices of your team. This is the list of the numbers of the agents (e.g., blue might be [1,3]).

getScore(self, gameState)

Returns how much you are beating the other team by in the form of a number that is the difference between your score and the opponent's score. This number is negative if you're losing.

getMazeDistance(self, pos1, pos2)

Returns the distance between two points; These are calculated using the provided distancer object. If distancer.getMazeDistances() has been called, then maze distances are available. Otherwise, this just returns Manhattan distance.

getPreviousObservation(self)

Returns the GameState object corresponding to the last state this agent saw (the observed state of the game last time this agent moved - this may not include all of your opponent's agent locations exactly).

def getCurrentObservation(self)

Returns the GameState object corresponding to this agent's current observation (the observed state of the game - this may not include all of your opponent's agent locations exactly).

debugDraw(self, cells, color, clear=False)

Draws a colored box on each of the cells you specify. If clear is True, will clear all old drawings before drawing on the specified cells. This is useful for debugging the locations that your code works with. cells: list of game positions to draw on (i.e. [(20,5), (3,22)]), color: list of RGB values between 0 and 1 (i.e. [1,0,0] for red).

Restrictions

You are free to design any agent you want. However, you will need to respect the provided APIs if you want to participate in the competition. Agents which compute during the opponent's turn will be disqualified. In particular, any form of multi-threading is disallowed, because we have found it very hard to ensure that no computation takes place on the opponent's turn.

Getting Started

By default, you can run a game with the simple baselineTeam that the staff has provided:

python capture.py

A wealth of options are available to you.  To see them, run:

python capture.py --help

There are four slots for agents, where agents 0 and 2 are always on the red team, and 1 and 3 are on the blue team. Agents are created by agent factories (one for Red, one for Blue). See the section on designing agents for a description of the agents invoked above. The only team that we provide is the baselineTeam. It is chosen by default as both the red and blue team, but as an example of how to choose teams:

python capture.py -r baselineTeam -b baselineTeam

which specifies that the red team -r and the blue team -b are both created from baselineTeam.py.  We recommend testing your team as both red and blue against the baselineTeam.  To control one of the four agents with the keyboard, pass the appropriate option:

python capture.py --keys0

The arrow keys control your character, which will change from ghost to Pacman when crossing the center line.

Layouts

By default, all games are run on the defaultcapture layout. To test your agent on other layouts, use the -l option. In particular, you can generate random layouts by specifying RANDOM[seed]. For example, -l RANDOM13 will use a map randomly generated with seed 13.

Recordings

You can record local games using the --record option, which will write the game history to a file named by the time the game was played. You can replay these histories using the --replay option and specifying the file to replay. 

Submissions and contest

To submit your team, upload your myTeam.py file to Gradescope.  We will run the contest at the end of the quarter.  The contest will be all-against-all (round-robin) with each combination of teams ran in 3 fixed and 3 random layouts.  Teams will be awarded 3 points per win, 1 point per tie, and 0 points per loss.  Failed games (your team fails to run successfully) are losses.  The contest rankings will be ordered by points first, number of wins second.  The final submissoin date 

Extra credit

Extra credit will be calculated based on your position in the contest rankings.  The following will be added to your overall percentage in the class at the end of quarter:

• 1st Place: 2.5% (guarantees a 0.1 increase in overall grade point)

• 2nd Place: 2.3%

• 3rd Place: 2.1%

• 4th to 10th Place: 1.9%

• 11th to 20th Place: 1.7%

• Above Baseline: 1.5% (roughly 50% chance of a 0.1 increase in overall grade point) 

Acknowledgements

Thanks to Barak Michener and Ed Karuna for providing improved graphics and debugging help.