Question

我用C实现了一个国际象棋游戏，结构如下：

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

移动 - 这是一个头尾移动的链接列表。

变量：   playing_color是'W'或'B'。   minimax_depth是之前设置的极小极大深度。

这是我使用alpha-beta修剪和getMoveScore函数的Minimax函数的代码，该函数应该返回之前设置的某个minimax_depth的Minimax树中的移动得分。

我也在使用getBestMoves函数，我将在这里列出它，它基本上可以找到Minimax算法中的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，我将在这里添加的三个函数中列出的所有函数都正常工作并经过测试，因此问题是alphabetaMax算法的逻辑问题或者实现 getBestMoves / getMoveScore。

问题主要在于，当我在深度N处获得最佳动作时（为什么还没有计算出来），然后使用getMoveScore函数检查相同深度的分数，我得到的分数不同于与那些实际最佳动作的得分相匹配。我花了好几个小时来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小费。

以下是代码：

/*
* 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Eugene指出的那样 - 我在这里添加一个例子： http://imageshack.com/a/img910/4643/fmQvlm.png

我现在是白人球员，我只有王-K和女王-q，相反的颜色有王-K和车-R。显然，我最好的举动是吃车或至少检查一下。部件的移动经过测试，工作正常。虽然当我在深度3调用get_best_moves函数时，我会在那个深度获得许多不必要的移动和负分数。也许现在它更清楚了。谢谢！

Answer 1

如果不调试整个代码，至少有一个问题是你的得分验证可能适用于minimax算法，而不适用于Alpha-Beta。以下问题：

getMoveScore（）函数必须以打开的AB Window开始。

然而，getBestMoves（）使用已关闭的AB窗口调用getMoveScore（）。

因此，在getBestMoves的情况下，可能存在未在getMoveScore（）中修剪的分支，因此分数不准确，这就是为什么这些值可能不同的原因（或至少其中一个）。

计算特定深度的最小极大树中的移动得分

1 个答案: