C#•8mo ago

❔ TicTacToe Minimax isnt working properly

Hello ive been trying to make a tictactoe game where the player plays against an AI that uses the minimax algorithm but the bot is making suboptimal moves and even after surfing the web i am confused as to why.. the methods i use to determine a move for the bot are

GetMove(); Minimax(); Eval()

GetMove(); Minimax(); Eval()

im attaching the whole code as a file

message.txt

16 Replies

JakenVeina•8mo ago

define "suboptimal moves"

Accord•8mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

Freez•8mo ago

the algorithm isnt taking the best moves in a given situation hence missing easy wins or losing when it could be easily avoided

JakenVeina•8mo ago

in a given situation

like what?

Freez•8mo ago

Freez•8mo ago

in this example where the bot is X and its his and everything in white is already in the game he would play the red X therefore missing the easy win with the green one

JakenVeina•8mo ago

excellent, let's run the algorithm for that state this is our move logic, yeah?

int maxEval = int.MinValue;

for (int y = 0; y < currentGame._size; y++)
{
    for (int x = 0; x < currentGame._size; x++)
    {
        if (currentGame.IsSafe(y, x))
        {
            currentGame._grid[y, x] = 'X';
            int eval = MiniMax(currentGame, 'O');
            currentGame._grid[y, x] = ' ';
            if (eval > maxEval)
            {
                maxEval = eval;
                _move = new int[] { y, x };
            }
        }
    }
}
return maxEval;

int maxEval = int.MinValue;

for (int y = 0; y < currentGame._size; y++)
{
    for (int x = 0; x < currentGame._size; x++)
    {
        if (currentGame.IsSafe(y, x))
        {
            currentGame._grid[y, x] = 'X';
            int eval = MiniMax(currentGame, 'O');
            currentGame._grid[y, x] = ' ';
            if (eval > maxEval)
            {
                maxEval = eval;
                _move = new int[] { y, x };
            }
        }
    }
}
return maxEval;

what happens for a game state of

  x 0 1 2
y
0   X O O
1   X
2

  x 0 1 2
y
0   X O O
1   X
2

Freez•8mo ago

we get a maxEval of 3 with a move of y=1, x=1 going from this

Freez•8mo ago

to this

Freez•8mo ago

(dont mind the cyan square its the player's indicator)

JakenVeina•8mo ago

why's that? it ought to be a 4 er rather the optimal move is a 4 for y=2, x=0 is that one not returning a 4, or is the 4 not getting captured properly?

Accord•8mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

Freez•8mo ago

i think it returned a 3 for it too when debugging but since its the same it didnt overwrite it as a better eval im not able to look into it today nor the first half of tomorrow but after that id be free if you're still eager to help resolve this issue in the meantime you could of course look into it on yoyr own if you'd like

JakenVeina•8mo ago

I have if the evaluation for y=2,x=0 is returning 3, then that's your problem. It should be 4.

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❔ TicTacToe Minimax isnt working properly