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我用 C 语言实现了一个国际象棋游戏，具有以下结构：

move - 表示在字符板上从 (a,b) 到 (c,d) 的移动[8][8]（棋盘）

move - 这是一个带有头部和尾部的动作的链接列表。

变量： playing_color 是 'W' 或 'B'。minimax_depth 是之前设置的 minimax 深度。

这是我的带有 alpha-beta 修剪的 Minimax 函数和 getMoveScore 函数的代码，它应该返回之前设置的某个 minimax_depth 的 Minimax 树中移动的分数。

我也在使用 getBestMoves 函数，我也会在这里列出，它基本上会在 Minimax 算法期间找到最佳移动并将它们保存到全局变量中，以便我以后可以使用它们。

我必须补充一点，我将在此处添加的三个函数中列出的所有函数都可以正常工作并经过测试，因此问题要么是alphabetaMax算法的逻辑问题，要么是getBestMoves/getMoveScore的实现。

问题主要是，当我在深度 N 处获得最佳移动（也没有正确计算）然后使用 getMoveScore 函数检查它们在相同深度上的分数时，我得到的分数与分数不匹配那些实际的最佳动作。我花了几个小时调试这个并且看不到错误，我希望也许有人可以给我一个关于找到问题的提示。

这是代码：

/*
* Getting best possible moves for the playing color with the minimax algorithm
*/
moves* getBestMoves(char playing_color){
    //Allocate memory for the best_moves which is a global variable to fill it in   a minimax algorithm//
    best_moves = calloc(1, sizeof(moves));
    //Call an alpha-beta pruned minimax to compute the best moves//
    alphabeta(playing_color, board, minimax_depth, INT_MIN, INT_MAX, 1);
    return best_moves;
}

/*
* Getting the score of a given move for a current player
*/
int getMoveScore(char playing_color, move* curr_move){
    //Allocate memory for best_moves although its not used so its just freed    later//
    best_moves = calloc(1, sizeof(moves));
    int score;
    char board_cpy[BOARD_SIZE][BOARD_SIZE];
    //Copying a a current board and making a move on that board which score I   want to compute//
    boardCopy(board, board_cpy);
    actualBoardUpdate(curr_move, board_cpy, playing_color);
    //Calling the alphabeta Minimax now with the opposite color , a board after     a given move and as a minimizing player, because basicly I made my move so  its now the opponents turn and he is the minimizing player//
    score = alphabeta(OppositeColor(playing_color), board_cpy, minimax_depth, INT_MIN, INT_MAX, 0);
    freeMoves(best_moves->head);
    free(best_moves);
    return score;
}

/*
* Minimax function - finding the score of the best move possible from the input board
*/
int alphabeta(char playing_color, char curr_board[BOARD_SIZE][BOARD_SIZE], int depth,int alpha,int beta, int maximizing) {
    if (depth == 0){
        //If I'm at depth 0 I'm evaluating the current board with my scoring            function//
        return scoringFunc(curr_board, playing_color);
    }
    int score;
    int max_score;
    char board_cpy[BOARD_SIZE][BOARD_SIZE];
    //I'm getting all the possible legal moves for the playing color//
    moves * all_moves = getMoves(playing_color, curr_board);
    move* curr_move = all_moves->head;
    //If its terminating move I'm evaluating board as well, its separate from depth == 0 because    only here I want to free memory//
    if (curr_move == NULL){
        free(all_moves);
        return scoringFunc(curr_board,playing_color);
    }
    //If maximizing player is playing//
    if (maximizing) {
        score = INT_MIN;
        max_score = score;
        while (curr_move != NULL){
            //Make the move and call alphabeta with the current board               after the move for opposite color and !maximizing player//
            boardCopy(curr_board, board_cpy);
            actualBoardUpdate(curr_move, board_cpy, playing_color);
            score = alphabeta(OppositeColor(playing_color), board_cpy, depth - 1,alpha,beta, !maximizing);
            
            alpha = MAX(alpha, score);
            if (beta <= alpha){
                break;
            }
            //If I'm at the maximum depth I want to get current player              best moves//
            if (depth == minimax_depth){
                move* best_move;
                //If I found a move with a score that is bigger then                    the max score, I will free all previous moves and                   append him, and update the max_score//
                if (score > max_score){
                    max_score = score;
                    freeMoves(best_moves->head);
                    free(best_moves);
                    best_moves = calloc(1, sizeof(moves));
                    best_move = copyMove(curr_move);
                    concatMoves(best_moves, best_move);
                }
                //If I have found a move with the same score and want                   to concatenate it to a list of best moves//
                else if (score == max_score){
                    best_move = copyMove(curr_move);
                    concatMoves(best_moves, best_move);
                }
                
            }
            //Move to the next move//
            curr_move = curr_move->next;
        }
        freeMoves(all_moves->head);
        free(all_moves);
        return alpha;
    }
    else {
        //The same as maximizing just for a minimizing player and I dont want       to look for best moves here because I dont want to minimize my          outcome//
        score = INT_MAX;
        while (curr_move != NULL){
            boardCopy(curr_board, board_cpy);
            actualBoardUpdate(curr_move, board_cpy, playing_color);
            score = alphabeta(OppositeColor(playing_color), board_cpy, depth - 1,alpha,beta, !maximizing);
            beta = MIN(beta, score);
            if (beta <= alpha){
                break;
            }
            curr_move = curr_move->next;
        }
        freeMoves(all_moves->head);
        free(all_moves);
        return beta;
    }
}

正如尤金指出的那样——我在这里添加一个例子：http: //imageshack.com/a/img910/4643/fmQvlm.png

我目前是白色玩家，我只有king-k和queen-q，相反的颜色有king-K和rook-R。显然，我在这里最好的举动是吃掉车或至少引起检查。棋子的移动经过测试，它们工作正常。虽然当我在深度 3 调用 get_best_moves 函数时，我在该深度得到了很多不必要的移动和负分数。也许现在它更清楚了。谢谢！

4

1 回答 1

0

在不调试整个代码的情况下，至少有一个问题是您的 scoreverification 可能适用于 minimax 算法，但不适用于 Alpha-Beta。以下问题：

getMoveScore() 函数必须从打开的 AB 窗口开始。

getBestMoves() 然而调用 getMoveScore() 与已经关闭的 AB 窗口。

因此，在 getBestMoves 的情况下，可能有一些分支没有在 getMoveScore() 中被修剪，因此分数不准确，这就是（或至少其中一个）这些值可能不同的原因。

于 2015-08-14T19:02:11.190 回答