我有以下奥赛罗(reversi)游戏的阿尔法-贝塔极小值的实现。不知怎的,这永远不会返回正确的行动。它似乎返回了我在函数(0,0)中设置的默认操作和第二个值-32768,这意味着它在MAX子例程中被删减了。关于我可以改进什么以及如何解决这个问题,有什么建议吗?
注意:我已经确定了大部分正确返回的继任者。目前的最大深度是8。电脑玩家的pn(玩家数量)是1,人类玩家的是0。第一阶段,0,是MINIMAX_MAX。阿尔法和贝塔最初分别设置为INT_MIN和INT_MAX。
mm_out minimax(Grid& G, int alpha, int beta, Action& A, uint pn, uint depth, bool stage) {
if (G.check_terminal_state() || depth == MAX_DEPTH) {
#ifdef DEBUG
cout << "best action: (" << A.get_x() << ", " << A.get_y() << ")\n";
#endif
return mm_out(A, G.get_utility(pn));
}
// add end game score total here
#ifdef DEBUG
if (stage == MINIMAX_MAX) {
cout << "max " << alpha << " " << beta << "\n";
}
else {
cout << "min " << alpha << " " << beta << "\n";
}
#endif
set<Action> succ_temp = G.get_successors(pn);
for (Action a : succ_temp) {
#ifdef DEBUG
cout << a.get_x() << " " << a.get_y() << '\n';
#endif
Grid gt(G);
a.evaluate(gt);
}
set<Action, action_greater> successors(succ_temp.begin(), succ_temp.end());
#ifdef DEBUG
Player p(0, "minimaxtest");
G.display(p);
int test;
cin >> test;
#endif
// if no successor, that player passes
if (successors.size()) {
for (auto a = successors.begin(); a != successors.end(); ++a) {
Grid gt(G);
gt.do_move(pn, a->get_x(), a->get_y(), !PRINT_ERR);
Action at = *a;
mm_out mt = minimax(gt, alpha, beta, at, pn ^ 1, depth + 1, !stage);
int temp = mt.val;
// A = mt.best_move;
if (stage == MINIMAX_MAX) {
if (alpha < temp) {
alpha = temp;
A = *a;
#ifdef DEBUG
cout << "Current action: (" << A.get_x() << ", " << A.get_y() << ") alpha = " << alpha << "\n";
#endif
}
if (alpha >= beta) {
#ifdef DEBUG
cout << "pruned at max\n";
#endif
return mm_out(A, beta);
}
}
else {
if (beta > temp) {
beta = temp;
A = *a;
#ifdef DEBUG
cout << "Current action: (" << A.get_x() << ", " << A.get_y() << ") beta = " << beta << "\n";
#endif
}
if (alpha >= beta) {
#ifdef DEBUG
cout << "pruned at min\n";
#endif
return mm_out(A, alpha);
}
}
}
return mm_out(A, (stage == MINIMAX_MAX) ? alpha : beta);
}
else {
cout << "no successor\n";
return mm_out(A, (stage == MINIMAX_MAX) ? (std::numeric_limits<int>::max() - 1) : (std::numeric_limits<int>::min() + 1));
}
}
实用功能:
int Grid::get_utility(uint pnum) const {
if (pnum)
return wcount - bcount;
return bcount - wcount;
}
您应该按值传递alpha
/beta
参数(而不是通过引用):
mm_out minimax(Grid& G, int alpha, int beta, Action& A, uint pn, uint depth, bool stage)
每个节点都将alpha和beta值传递给其子节点。然后,子节点根据轮到谁更新自己的alpha或beta值副本,并返回该节点的最终评估。然后用于更新父级的alpha或beta值。