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copied!<p>The main issue here is I believe the usage of object variables instead of local variable.</p> <p><code>self.move</code> is an <em>object variable</em>, every time you change it - every level of the recursion "sees" the change, which is usually a bad thing for recursive algorithms.</p> <p>Recursive algorithms should be self contained, and do minimal if any change on the calling environment - it makes it much easier to walk over the flow of the algorithm.</p> <p>The two main issues I see in this code are:</p> <ol> <li><code>self.move</code> should be a <em>local</em> variable (declare it as <code>move</code>). When you later do: <code>board.unmakeMove(self.move, player)</code> - I suspect that the board is undoing a different move, which was set deeper in the recursion tree, and not the one you intended. Using a local variable will eliminate this undesired behavior.</li> <li>Each level of the recursive call is setting <code>self.max_eval = float('-infinity')</code> - so you constantly change it, though it is probably not what you want to do.</li> </ol> <p>The solution should be something like that:</p> <pre><code>def negaMax(self, board, rules, ply, player): """ Implements a minimax algorithm. """ if ply == 0: return self.positionEvaluation() max_eval = float('-infinity') move_list = board.generateMoves(rules, player) for move in move_list: board.makeMove(move, player) currentEval = -self.negaMax(board, rules, ply - 1, board.getOtherPlayer(player)) board.unmakeMove(move, player) if currentEval > max_eval: max_eval = currentEval return max_eval </code></pre> <p>I am not 100% certain it will indeed solve everything in the code (but it will solve some of it) but I am 100% certain avoiding object variables will make your code much easier to understand and debug.</p>

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