为Hexgame C ++制作Monte Carlo eval多线程

Question

我正在努力使我的蒙特卡罗评估功能成为多线程，因此我的hexgame中的计算机播放器会更快。普通代码（没有多线程）是：

using namespace std;

int getMonteCarloEval(const State &board, Player player, int trials)
{
    vector<Move> moves = board.getMoves();
    int wins = 0;

    for (int i = 0; i < trials; ++i)
    {
        State mcBoard = board;

        random_shuffle(moves.begin(), moves.end());
        for (const Move &m : moves)
            mcBoard.doMove(m);
        if (mcBoard.getWinner() == player)
            wins++;
    }

    return wins - trials / 2;
}

int getRandomEval(const State &board, Player)
{
    return rand() % 101 - 50;
}

使用多线程我有这个：

using namespace std;
vector<Move> moves;
atomic<int> wins = 0;

int getMonteCarloEval(const State &board, Player player, int trials)
{
    vector<Move> moves = board.getMoves();
    State mcBoard = board;
    size_t nr_threads = 8;
    vector<thread> workers;

    int delta = trials / nr_threads;
    int remainder = trials % nr_threads;
    int L = 0; int R = 0;

    for (int i = 0; i < nr_threads; i++) {
        R = L + delta;
        if (i == nr_threads - 1)
            R += remainder;
        workers.push_back(thread(mc, mcBoard, player, L, R));
        L = R;
    }
    for (auto &thread : workers) {
        thread.join();
    }

    return wins - trials / 2;
}

int getRandomEval(const State &board, Player)
{
    return rand() % 101 - 50;
}

int mc(const State &board, Player player, int L, int R)
{
    for (int i = L; i < R; i++)
    {
        State mcBoard = board;
        random_shuffle(moves.begin(), moves.end());
        for (Move m : moves)
            mcBoard.doMove(m);
        if (mcBoard.getWinner() == player)
            wins++;
    }
}

这里的问题是，现在的计算机播放器确实非常愚蠢。如果没有多线程，计算机播放器的播放速度非常慢。 我还使用Alpha Berta修剪来搜索计算机的最佳下一步。

问题：有人知道我在使用MultiThreading时遇到了什么问题吗？