c# - 为什么此代码会为(看起来是)相同的输入提供两个不同的输出？

Question

我正在尝试为跳棋游戏编写一些 AI 程序。我的程序说白色玩家有 0 步，即使我知道有。 GetValidMoves() 函数已经过测试，可以在代码的其他区域使用。

为了尝试隔离程序，我保存了有问题的板状态，然后将其重新加载以查看我是否会遇到同样的问题:

using(Stream s = File.Open("board.dat", FileMode.Create))
{
    var bf = new BinaryFormatter();
    bf.Serialize(s, board);
}
Debug.WriteLine(board.GetValidMoves(Color.White).Count());

using (Stream s = File.Open("board.dat", FileMode.Open))
{
    var bf = new BinaryFormatter();
    board = (Board)bf.Deserialize(s);
}
Debug.WriteLine(board.GetValidMoves(Color.White).Count());

这打印:

0
7

当我期望输出相同时(7 是正确的)。

什么会导致它在反序列化后开始工作？董事会的两个实例似乎完全相同......我打印出所有属性并且它们都一样正确。我不确定从这里到哪里去？

板的第一个实例(在反序列化之前)是克隆的结果。我可能克隆错了吗？是否存在“悬挂引用”？

---

GetValidMoves:

    public IEnumerable<Move> GetValidMoves(Color c)
    {
        var jumps = GetJumps(c);
        if (jumps.Any())
            foreach (var j in jumps)
                yield return j;
        else
            foreach (var s in GetSlides(c))
                yield return s;
    }

    public IEnumerable<Move> GetSlides(Color c)
    {
        foreach (int i in Enumerate(c))
            foreach (var s in GetSlides(c, i))
                yield return s;
    }

    public IEnumerable<Move> GetJumps(Color c)
    {
        foreach (int i in Enumerate(c))
            foreach (var j in GetJumps(c, i))
                yield return j;
    }

    public IEnumerable<Move> GetJumps(Color c, int i)
    {
        Checker checker = this[c, i] as Checker;
        bool indentedRow = i % Width < rowWidth;
        int column = i % rowWidth;
        int offset = indentedRow ? 0 : -1;
        bool againstLeft = column == 0;
        bool againstRight = column == rowWidth - 1;
        int moveSW = i + rowWidth + offset;
        int moveSE = moveSW + 1;
        int jumpSW = i + rowWidth * 2 - 1;
        int jumpSE = jumpSW + 2;

        if (!againstLeft && jumpSW < Count && IsEnemy(c, moveSW) && IsEmpty(c, jumpSW))
            yield return new Move(c, i, jumpSW, jump: true, crown: IsCrowned(checker, jumpSW));
        if (!againstRight && jumpSE < Count && IsEnemy(c, moveSE) && IsEmpty(c, jumpSE))
            yield return new Move(c, i, jumpSE, jump: true, crown: IsCrowned(checker, jumpSE));

        if (checker.Class == Class.King)
        {
            int moveNW = i - rowWidth + offset;
            int moveNE = moveNW + 1;
            int jumpNW = i - rowWidth * 2 - 1;
            int jumpNE = jumpNW + 2;

            if (!againstLeft && jumpNW >= 0 && IsEnemy(c, moveNW) && IsEmpty(c, jumpNW))
                yield return new Move(c, i, jumpNW, jump: true);
            if (!againstRight && jumpNE >= 0 && IsEnemy(c, moveNE) && IsEmpty(c, jumpNE))
                yield return new Move(c, i, jumpNE, jump: true);
        }
    }

    public IEnumerable<Move> GetSlides(Color c, int i)
    {
        Checker checker = this[c, i] as Checker;
        bool indentedRow = i % Width < rowWidth;
        int column = i % rowWidth;
        int offset = indentedRow ? 0 : -1;
        bool againstLeft = !indentedRow && column == 0;
        bool againstRight = indentedRow && column == rowWidth - 1;
        int moveSW = i + rowWidth + offset;
        int moveSE = moveSW + 1;

        if (!againstLeft && moveSW < Count && IsEmpty(c, moveSW))
            yield return new Move(c, i, moveSW, crown: IsCrowned(checker, moveSW));
        if (!againstRight && moveSE < Count && IsEmpty(c, moveSE))
            yield return new Move(c, i, moveSE, crown: IsCrowned(checker, moveSE));

        if (checker.Class == Class.King)
        {
            int moveNW = i - rowWidth + offset;
            int moveNE = moveNW + 1;

            if (!againstLeft && moveNW >= 0 && IsEmpty(c, moveNW))
                yield return new Move(c, i, moveNW, crown: IsCrowned(checker, moveNW));
            if (!againstRight && moveNE >= 0 && IsEmpty(c, moveNE))
                yield return new Move(c, i, moveNE, crown: IsCrowned(checker, moveNE));
        }
    }

它不应该有副作用。

---

回答您关于有效移动是否无意中改变棋盘状态的问题:

            var board = new Board(8, 8);
            board.SetUp();
            foreach(var m in board.GetValidMoves(Color.White))
                Console.WriteLine(m);
            Console.WriteLine("---");
            foreach(var m in board.GetValidMoves(Color.White))
                Console.WriteLine(m);

打印:

8-12
8-13
9-13
9-14
10-14
10-15
11-15
---
8-12
8-13
9-13
9-14
10-14
10-15
11-15

(相同的输出两次)如您所料。

Answer 1

只是一个大胆的猜测，但您是否确定调用 GetValidMoves 绝对没有副作用？

由于您在调用 GetValidMoves 之后序列化和反序列化电路板，因此 GetValidMoves 似乎以某种方式更改了电路板(考虑到函数名称，这对我来说似乎有点奇怪)。所以也许还有其他您没有考虑到的副作用。