Assignment 4

Programming Assignment - Game Playing Algorithms

Task

The task in this programming assignment is to implement an agent that plays the Max-Connect4 game using search. Figure 1 shows the first few moves of a game. The game is played on a 6x7 grid, with six rows and seven columns. There are two players, player A (red) and player B (green). The two players take turns placing pieces on the board: the red player can only place red pieces, and the green player can only place green pieces.

It is best to think of the board as standing upright. We will assign a number to every row and column, as follows: columns are numbered from left to right, with numbers 1, 2, ..., 7. Rows are numbered from bottom to top, with numbers 1, 2, ..., 6. When a player makes a move, the move is completely determined by specifying the COLUMN where the piece will be placed. If all six positions in that column are occupied, then the move is invalid, and the program should reject it and force the player to make a valid move. In a valid move, once the column is specified, the piece is placed on that column and "falls down", until it reaches the lowest unoccupied position in that column.

The game is over when all positions are occupied. Obviously, every complete game consists of 42 moves, and each player makes 21 moves. The score, at the end of the game is determined as follows: consider each quadruple of four consecutive positions on board, either in the horizontal, vertical, or each of the two diagonal directions (from bottom left to top right and from bottom right to top left). The red player gets a point for each such quadruple where all four positions are occupied by red pieces. Similarly, the green player gets a point for each such quadruple where all four positions are occupied by green pieces. The player with the most points wins the game.

Your program will run in two modes: an interactive mode, that is best suited for the program playing against a human player, and a one-move mode, where the program reads the current state of the game from an input file, makes a single move, and writes the resulting state to an output file. The one-move mode can be used to make programs play against each other. Note that THE PROGRAM MAY BE EITHER THE RED OR THE GREEN PLAYER, THAT WILL BE SPECIFIED BY THE STATE, AS SAVED IN THE INPUT FILE.

As part of this assignment, you will also need to measure and report the time that your program takes, as a function of the number of moves it explores. All time measurements should report CPU time, not total time elapsed. CPU time does not depend on other users of the system, and thus is a meaningful measurement of the efficiency of the implementation.
Sample Max-Connect Game
Figure 1: Sample Max-Connect Game (15 moves in)

Interactive Mode

In the interactive mode, the game should run from the command line with the following arguments (assuming a Java implementation, with obvious changes for C++ or other implementations):

java maxconnect4 interactive [input_file] [computer-next/human-next] [depth]

For example:

java maxconnect4 interactive input1.txt computer-next 7
After reading the input file, the program gets into the following loop:
  1. If computer-next, goto 2, else goto 5.
  2. Print the current board state and score. If the board is full, exit.
  3. Choose and make the next move.
  4. Save the current board state in a file called computer.txt (in same format as input file).
  5. Print the current board state and score. If the board is full, exit.
  6. Ask the human user to make a move (make sure that the move is valid, otherwise repeat request to the user).
  7. Save the current board state in a file called human.txt (in same format as input file).
  8. Goto 2.

One-Move Mode

The purpose of the one-move mode is to make it easy for programs to compete against each other, and communicate their moves to each other using text files. The one-move mode is invoked as follows:

java maxconnect4 one-move [input_file] [output_file] [depth]

For example:

java maxconnect4 one-move red_next.txt green_next.txt 5

In this case, the program simply makes a single move and terminates. In particular, the program should:

Sample code

The sample code needs an input file to run. Sample input files that you can download are input1.txt and input2.txt. You are free to make other input files to experiment with, as long as they follow the same format. In the input files, a 0 stands for an empty spot, a 1 stands for a piece played by the first player, and a 2 stands for a piece played by the second player. The last number in the input file indicates which player plays NEXT (and NOT which player played last). Sample code is available in: The sample code implements a system playing max-connect4 (in one-move mode only) by making random moves. While the AI part of the sample code leaves much to be desired (your assignment is to fix that), the code can get you started by showing you how to represent and generate board states, how to save/load the game state to and from files in the desired format, and how to count the score (though faster score-counting methods are possible).

Measuring Execution Time

You can measure the execution time for your program on omega by inserting the word "time" in the beginning of your command line. For example, if you want to measure how much time it takes for your system to make one move with the depth parameter set to 10, try this:

time java maxconnect4 one-move red_next.txt green_next.txt 10

Your output will look something like:
    real    0m0.003s
    user    0m0.002s
    sys     0m0.001s

Out of the above three lines, the user line is what you should report.

Grading

The assignments will be graded out of 100 points. There is also upto 15 possible extra credit points.

How to submit

Implementations in C, C++, Java, and Python will be accepted. If you would like to use another language, make sure it will compile on omega and clear it with the instructor beforehand. Points will be taken off for failure to comply with this requirement.
The assignment should be submitted via Blackboard. Submit a ZIPPED directory called assignment4_<net-id>.zip (no other forms of compression accepted, contact the instructor or TA if you do not know how to produce .zip files). The directory should contain source code. Including binaries that work on omega (for Java and C++) is optional. The submission should also contain a file called readme.txt, which should specify precisely:

Submission checklist

Is the code running on omega?
Does the submission include eval_explanation.txt?
Does the submission include the table of depth limit vs runtime?
Does the submission include a readme.txt file, as specified?