tinanemati / connect_4_ai

Connect 4 AI Application with 80% winning ability (ECS 170 SS'2 UCD)

AI Project

Part I: Evaluation Function

Estimating how "good" a state is for us(or how "bad" a state is for the opponent) based on number of consecutive pieces and weighted each term while considering the opponent's pieces.

There were roughly five tasks completed here:

1. Count the num of 3's, 2's and 1's for self.position in each row, column and diagonals.

2. Count the num of 3's, 2's and 1's for self.opponent.position in each row, column and diagonals.

3. Store the count in two dictionaries.

   • Example: output_dict['3': 1, '2':2, '1':5] for self and output_dict2['3': 1, '2':2, '1':5] for opponent.

4. Calculate the score using the bellow function:

   • Note that the weight for the num of 3's consecative pieces is higher than 2's consecative pieces to assure we are blocking the opponet's move and priotizing the 3's pieces to 2's.

res_self = 1 * output_dict.get(1, 0) + 25 * output_dict.get(2, 0) + 100 * output_dict.get(3, 0)
res_opponent = 1 * output_dict2.get(1, 0) + 25 * output_dict2.get(2,0)+ 100 * output_dict2.get(3, 0)

5. Return the score --> res_self-res_opponent

Part II: Coding the Agent

Using minimax with alpha-beta pruning, code your algorithm to play the game.

To make things easier and faster for us to read and go over the code, we took advantage of the professor's implementaion of min and max in PA2 helper video.

we have methods called: def MAX(self, env, prev_move, depth, alpha, beta)and def MIN(self, env, prev_move, depth, alpha, beta) that return the updated value of 'MIN and updated value of MAX for us, so we are able to store that in max_vand min_v variables. Afterwards, we will save and
make the next move using our driver function.

Using our minimax implementation with alpha-beta pruning, allowed us to play faster since we are able to prune some nodes and don't go through them, as result we are winning most of the 20 games.

In order to imrpove the efficiency of our program:

1. we decided to change the weight of our evalution function, to be able to block the opponent, this helped us play much faster and better.
2. we decided to play around with our depth, having depth of 3 and 5 was too high for our minimax to select the best move, so we decreased it to 2.
3. we decided to order our nodes in the most optimal order(center column gets evaluted first and then we move to edge columns [3,2,4,1,5,0,6] instead of [0,1,2,3,4,5,6], however, after implementation we noticed that our agent hasn't imrpoved as much and as a matter of fact, we are losing more games, so we decided to put it back to the prev implementation.

Part III: Evaluation Function

Evaluate your agent against the benchmark agents.

● OurAgent vs StupidAI:

games	OurAgent - p1 vs. StupidAI -p2	StupidAI - p1 vs. OurAgent - p2
game 1	p1 wins	p2 wins
game 2	p1 wins	p2 wins

● OurAgent vs RandomAI -- 5 times:

games	OurAgent - p1 vs. RandomAI -p2	RandomAI - p1 vs. OurAgent - p2
seed 0	p1 wins	p2 wins
seed 1	p1 wins	p2 wins
seed 2	p1 wins	p2 wins
seed 3	p1 wins	p2 wins
seed 4	p1 wins	p2 wins

● OurAgent vs MonteCarloAI -- 10 times:

games	OurAgent - p1 vs. MonteCarloAI -p2	MonteCarloAI - p1 vs. OurAgent - p2
seed 0	p1 wins	p2 wins
seed 1	p1 wins	p2 loses
seed 2	p1 wins	p2 wins
seed 3	p1 wins	p2 wins
seed 4	p1 wins	p2 wins
seed 5	p1 wins	p2 wins
seed 6	p1 wins	p2 wins
seed 7	p1 wins	p2 wins
seed 8	p1 wins	p2 wins
seed 9	p1 wins	p2 wins