人机博弈程序实现

本文由恋花蝶最初发表于http://blog.csdn.net/lanphaday上，您可以转载、引用、打印和分发等，但必须保留本文完整和包含本声明，否则必究责任。

到昨天晚上，Topcoder Marathon Match 6结束了，我取得了第18名的成绩，已经是自己参加Marathon四次以来的最好名次啦，高兴ing，这次终于中国人的成绩超过日本人了。因为这次的题 目比较偏：写一个人工智能程序和服务器端的程序进行博弈。人机博弈是一门比较专的学科，我们因为英文劣势，大部分中国高手都不能快速的在比赛中学习和实现 一些复杂的算法，以致成绩不太如意；我挟之前对这方面的了解，做得还算行，所以把代码公开出来，可以多一点中文方面的资料和源码给大家参考，我也感到非常 荣幸。
比赛的题目请看这里：http://www.topcoder.com/longcontest/?module=ViewProblemStatement&rd=10118&pm=6759 主要的游戏规则也是在这里的，我就不在这里重复啦，主要讲讲我的代码用到了什么算法。麻将虽小，五脏俱全，主要应用的算法有主要变量搜索(PVS)、历史 启发(HH)、杀手启发(KH)、Null Move和迭代深化(ID)，可惜后来不够时间实现置换表(TT)，不然可以多一个算法了。代码里还实现了时间控制策略，可以几乎用尽20秒的测试时间， 为争取更好的着法提供了保证。还有值得一提的是棋盘表示，我使用了棋盘表、棋子位置表结合的方式来表示，后来发现加上空位表的话，可以加快不少走法生成和 估值的速度。反正棋盘表示是一切的基础，一种好的表示方法可以带来很大的性能提升。对于代码，大家注意class SE里的search_move和pvs两个函数，上述的算法和策略都在那里。class MG是关于棋盘表示、走法生成和估值的，class KH和class HH分别是杀手启发和历史启发。Null Move是简单有效的算法，不过我的实现里是比较简单的那种，如果有兴趣，可以查询其它资料。

讲了这么多，应该说一下这份代码的计算 能力：以6*6的棋盘为例，这份代码在VC6的release模式下编译运行可以在1秒内搜索并评估83万个叶子节点，计算层次在8-9层；如果用 MiniMax算法不进行剪枝，只能搜索到3-4层（测试机器皆为超线程P4 3.0G＋1G内存）。这就是算法的力量吧。另声明一下，本代码未作优化，不代表我不懂，只是没有时间，看的朋友请海涵了。

下面是代码，在VC和G++上皆可编译、执行

因为比赛期间写的，代码比较乱，但整体的风格还是可以的，复制到IDE上看可能会更好看些

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <cassert>
#include <vector>
#include <algorithm>

using namespace std;

typedef unsigned int UINT;
typedef UINT MOVE;

const int INFINITY = 100000000;
const int MAX_DEPTH = 16;

const UINT max_board_size = 256;
const UINT max_stones_cnt = 256;

const UINT empty = 0;
const UINT my_color = 1;
const UINT svr_color = 2;

#ifdef WIN32
const clock_t all_time = 19200;
#else
const clock_t all_time = 19200000;
#endif

const UINT check_time_cnt = 0x00001fff;

#define is_empty(x) (x==empty)

#define opp_color(x) (x==my_color?svr_color:my_color)

int leaf_cnt = 0;

class MG
{
private:
UINT N_;
UINT board_[max_board_size];
UINT stones_[max_stones_cnt];
private:
void extend(UINT pos, unsigned char* eht, unsigned char* est, UINT& area, UINT& round);

public:
MOVE move_table[MAX_DEPTH][max_board_size];
UINT curr_stones_cnt;
UINT curr_board_size;
void set_N(int n)...{
N_ = n;
curr_board_size = n*n;
curr_stones_cnt = 0;
memset(board_, 0, sizeof(UINT)*max_board_size);
memset(stones_, 0, sizeof(UINT)*max_stones_cnt);
}
void make_move(int idx, int color)...{
board_[idx]=color;
stones_[curr_stones_cnt++] = idx;
}
void unmake_move(int idx)...{
board_[idx] = empty;
--curr_stones_cnt;
}
inline bool is_game_over()...{return curr_stones_cnt == curr_board_size;}
UINT gen_move(int depth);
int evaluatoin(int color);
int evaluatoin_4_end(int color);
void print_board()
...{
int cnt = 0;
for(UINT i = 0; i < curr_board_size; ++i)
...{
if(is_empty(board_[i]))
cout << "o ";
else
cout << ((board_[i]==my_color)?"@ ":"- ");
++cnt;
if(cnt == N_)
...{
cnt = 0;
cout << endl;
}
}
}
bool can_move(MOVE move)...{return is_empty(board_[move]);}
void remove_killers(int depth, int move_cnt, MOVE* killers, int killers_cnt)
...{
for(int i = 0; i < killers_cnt; ++i)
...{
MOVE m = killers[i];
for(int j = 0; j < move_cnt; ++j)
...{
if(move_table[depth][j] != m)
continue;
for(int k = j+1; k < move_cnt; ++k)
...{
move_table[depth][k-1] = move_table[depth][k];
}
break;
}
}
}
};

UINT MG::gen_move(int depth)
{
int cnt = 0;
for(UINT i = 0; i < curr_board_size; ++i)
...{
if(is_empty(board_[i]))
move_table[depth][cnt++] = i;
}
return cnt;
}

int MG::evaluatoin(int color)
{
if(curr_stones_cnt+1 == curr_board_size)
...{
for(int i = 0; i < curr_board_size; ++i)
...{
if(is_empty(board_[i]))
...{
board_[i] = color;
int value = -evaluatoin_4_end(opp_color(color));
board_[i] = empty;
return value;
}
}
}
++leaf_cnt;
unsigned char extended_hash_table[max_board_size] = ...{0};

int my_score = 0, svr_score = 0;
for(UINT i = 0; i < curr_stones_cnt; ++i)
...{
UINT pos = stones_[i];
if(extended_hash_table[pos])
continue;
UINT area = 0, round = 0;
unsigned char extended_space_table[max_board_size] = ...{0};
extend(pos, extended_hash_table, extended_space_table, area, round);
if(board_[pos] == my_color)
...{
my_score += area*area*round;
}
else
...{
svr_score += area*area*round;
}
}
if(color == my_color)
return my_score - svr_score;
return svr_score - my_score;
}

int MG::evaluatoin_4_end(int color)
{
++leaf_cnt;
unsigned char extended_hash_table[max_board_size] = ...{0};

int my_score = 0, svr_score = 0;
for(UINT i = 0; i < curr_stones_cnt; ++i)
...{
UINT pos = stones_[i];
if(extended_hash_table[pos])
continue;
UINT area = 0, round = 0;
unsigned char extended_space_table[max_board_size] = ...{0};
extend(pos, extended_hash_table, extended_space_table, area, round);
if(board_[pos] == my_color)
...{
my_score += area*area;
}
else
...{
svr_score += area*area;
}
}
if(color == my_color)
return my_score - svr_score;
return svr_score - my_score;
}

void MG::extend(UINT pos, unsigned char* eht, unsigned char* est, UINT& area, UINT& round)
{
const UINT round_cnt = 4;
int is[round_cnt] = ...{-N_, -1, 1, N_};

++area;
eht[pos] = 1;

for(UINT i = 0; i < round_cnt; ++i)
...{
int new_idx = pos + is[i];
if(new_idx < 0 || new_idx >= curr_board_size)
continue;
if(i == 1 && pos % N_ == 0)
continue;
if(i == 2 && new_idx % N_ == 0)
continue;
if(is_empty(board_[new_idx]) && (!est[new_idx]))
...{
++round;
est[new_idx] = 1;
continue;
}
if(eht[new_idx])
continue;
if(board_[new_idx] == board_[pos])
extend(new_idx, eht, est, area, round);
}
}

class HH
{
private:
UINT board_[2][max_board_size];
public:
void reset()...{memset(board_, 0, sizeof(UINT)*max_board_size);}
void update_value(int depth, int color, MOVE move);
MOVE get_best(MOVE* move_list, int color, int cnt);
};

void HH::update_value(int depth, int color, MOVE move)
{
board_[color-1][move] += (1 << depth);
}

MOVE HH::get_best(MOVE* move_list, int color, int cnt)
{
int real_color = color-1;
MOVE* p = move_list;
int best = board_[real_color][*move_list];
int best_idx = 0;
for(int i = 1; i < cnt; ++i)
...{
++move_list;
if(board_[real_color][*move_list] <= best)
continue;
best = board_[real_color][*move_list];
best_idx = i;
}
MOVE tmp = *p;
*p = p[best_idx];
p[best_idx] = tmp;
return *p;
}

struct KH_item
{
MOVE move;
int cnt;
};

class less_than
{
public:
inline bool operator()(const KH_item& lhs, const KH_item& rhs)
...{
return lhs.cnt < rhs.cnt;
}
};

const int max_kh_item_cnt = 4;

class KH
{
private:
KH_item KH_table[MAX_DEPTH][max_kh_item_cnt];
int cnt_table[MAX_DEPTH];
public:
void add_to_kh(MOVE move, int depth)
...{
int cnt_mini_idx = 0;
int cnt_mini = KH_table[depth][0].cnt;
int i = 0;
for(i = 0; i < cnt_table[depth]; ++i)
...{
KH_item& tmp = KH_table[depth][i];
if(tmp.move == move)
...{
++tmp.cnt;
return;
}
if(tmp.cnt < cnt_mini)
...{
cnt_mini_idx = i;
cnt_mini = tmp.cnt;
}
}
if(i < max_kh_item_cnt)
...{
KH_table[depth][i].move = move;
++(cnt_table[depth]);
}
else
...{
KH_item& tmp = KH_table[depth][cnt_mini_idx];
tmp.move = move;
tmp.cnt = 1;
}
}
int get_killers(MOVE* killers, int depth)
...{
sort<KH_item*>(KH_table[depth], KH_table[depth]+cnt_table[depth], less_than());
int i = 0;
for(i = 0; i < cnt_table[depth]; ++i)
...{
killers[i] = KH_table[depth][i].move;
}
return i;
}
void reset()
...{
memset(cnt_table, 0, sizeof(int)*MAX_DEPTH);
memset(KH_table, 0, sizeof(KH_item)*MAX_DEPTH*max_kh_item_cnt);
}
};

class SE
{
private:
MG mg;
HH hh;
KH kh;
int N_;
int best_move;
int max_depth_;
public:
void print_board()
...{
mg.print_board();
}
void set_N(int N)
...{
N_ = N;
used_time = 0;
best_move = 0xffff;
mg.set_N(N);
}
vector<int> get_best_move()
...{
int row = best_move / N_;
int col = best_move % N_;
vector<int> move;
move.push_back(row);
move.push_back(col);
return move;
}
void do_move(int row, int col, int color)
...{
mg.make_move(row*N_+col, color);
}
void make_sure_best_move_first(MOVE* moves, int cnt, MOVE best_move);
vector<int> search_move(int max_depth);
int pvs(int, int, int, int, int);
private:
clock_t bgn_time;
clock_t used_time;
clock_t curr_time_limit;
};

void SE::make_sure_best_move_first(MOVE* moves, int cnt, MOVE best_move)
{
for(int i = 0; i < cnt; ++i)
...{
if(moves[i] == best_move)
...{
moves[i] = moves[0];
moves[0] = best_move;
}
}
}

vector<int> SE::search_move(int max_depth)
{
leaf_cnt = 1;
bgn_time = clock(); //³õʼʱ¼ä
//¼ÆËã±¾´ÎʱÏÞ
UINT leave_space_cnt = mg.curr_board_size - mg.curr_stones_cnt;
if(leave_space_cnt >= 2)
leave_space_cnt /= 2;
curr_time_limit = (all_time - used_time) / leave_space_cnt;
if(curr_time_limit > all_time || curr_time_limit < 0)
...{
curr_time_limit = 1;
}

if(leave_space_cnt < mg.curr_board_size/3)
curr_time_limit = ((double)curr_time_limit) * (1.4);
else if(leave_space_cnt < mg.curr_board_size/2)
curr_time_limit = ((double)curr_time_limit) * (1.3);

if(N_ > 12)
curr_time_limit = ((double)curr_time_limit) * (0.9);

hh.reset();
kh.reset();
int md = 0;
int backup_max_depth = max_depth;
while(md < max_depth)
...{
++md;
max_depth_ = md;
pvs(md, my_color, 0, -INFINITY, INFINITY);

if(max_depth >= backup_max_depth)
...{
//»¹ÓÐʱ¼ä£¿
if(clock()-bgn_time < curr_time_limit)
...{
//²»»á¶ÑÕ»Òç³ö£¿ÔÙËã¶àÒ»²ã
if(max_depth < MAX_DEPTH - 1)
++max_depth;
}
}
if(clock()-bgn_time >= curr_time_limit)
...{
break;
}
}
clock_t curr_used = clock() - bgn_time;
used_time += curr_used; //Ôö¼ÓÓõôµÄʱ¼ä
return get_best_move();
}

int SE::pvs(int depth, int color, int nullmove, int alpha, int beta)
{
if(mg.is_game_over())
return mg.evaluatoin_4_end(color);
if(depth <= 0)
return mg.evaluatoin(color);
if((leaf_cnt & check_time_cnt) == 0) //¼ì²âÊÇ·ñ³¬Ê±
...{
if(clock()-bgn_time >= curr_time_limit)
return mg.evaluatoin(color);
}

// Null Move
if(depth < max_depth_ && nullmove == 0)
...{
int value = -pvs(depth-2, opp_color(color), 1, -alpha-1, -alpha);
if(value >= beta)
...{
return value;
}
}

// killer move
int best;
MOVE bm = 0xffff;
MOVE killers[max_kh_item_cnt];
int killers_cnt = kh.get_killers(killers, depth);

if(killers_cnt > 0 && depth == max_depth_)
make_sure_best_move_first(killers, killers_cnt, best_move);

for(int k = 0; k < killers_cnt; ++k)
...{
MOVE m = killers[k];
if(!mg.can_move(m))
continue;
mg.make_move(m, color);
best = -pvs(depth-1, opp_color(color), 0, -alpha-1, -alpha);
if(best >= beta)
...{
if(depth == max_depth_)
best_move = m;
kh.add_to_kh(m, depth);
hh.update_value(depth, color, m);
mg.unmake_move(m);
return best;
}
else if(best > alpha)
...{
alpha = best;
bm = m;
}
mg.unmake_move(m);
if((leaf_cnt & check_time_cnt) == 0) //¼ì²âÊÇ·ñ³¬Ê±
...{
if(clock()-bgn_time >= curr_time_limit)
break;
}
}

// PVS
int move_cnt = mg.gen_move(depth);

if(depth == max_depth_)
make_sure_best_move_first(mg.move_table[depth], move_cnt, best_move);

if(killers_cnt == 0 || bm == 0xffff) // bm == 0xffff±íʾkillersÎÞЧ£¡
...{
if(depth == max_depth_)
bm = mg.move_table[depth][0];
else
bm = hh.get_best(mg.move_table[depth], color, move_cnt);
mg.make_move(bm, color);
best = -pvs(depth-1, opp_color(color), 0, -beta, -alpha);
mg.unmake_move(bm);
}
else
...{
// remove killers from move_table
if(killers_cnt > 0)
mg.remove_killers(depth, move_cnt, killers, killers_cnt);
MOVE bm_;
if(depth == max_depth_)
bm_ = mg.move_table[depth][0];
else
bm_ = hh.get_best(mg.move_table[depth], color, move_cnt);
mg.make_move(bm_, color);
int best_ = -pvs(depth-1, opp_color(color), 0, -beta, -alpha);
if(best_ > best)
...{
best = best_;
bm = bm_;
}
mg.unmake_move(bm_);
}
for(int i = 1; i < move_cnt; ++i)
...{
if(best >= beta)
break;
if(best > alpha)
alpha = best;

if((leaf_cnt & check_time_cnt) == 0) //¼ì²âÊÇ·ñ³¬Ê±
...{
if(clock()-bgn_time >= curr_time_limit)
break;
}

MOVE m = hh.get_best(mg.move_table[depth]+i, color, move_cnt-i);
mg.make_move(m, color);
int value = -pvs(depth-1, opp_color(color), 0, -alpha-1, -alpha);
if(value > alpha && value < beta)
...{
best = -pvs(depth-1, opp_color(color), 0, -beta, -value);
bm = m;
}
else if(value > best)
...{
best = value;
bm = m;
}
mg.unmake_move(m);
}
if(depth == max_depth_)
best_move = bm;
if(best >= alpha)
...{
kh.add_to_kh(bm, depth);
hh.update_value(depth, color, bm);
}
return best;
}

class PseudoTonga
{
public:
vector<int> move(int row, int col);
vector<int> init(int N, int row, int col);
private:
int N_;
SE se;
void do_move(int row, int col, int color);
};

vector<int> PseudoTonga::init(int N, int row, int col)
{
N_ = N;
se.set_N(N);

int r = 0, c = 0;

if(row >= 0 || col >= 0)
...{
return move(row, col);
}

vector<int> move;
r = c = N/2;
do_move(r, c, my_color);
move.push_back(r);
move.push_back(c);
cout << "player: row = " << move[0] << ", col = " << move[1] << "; " ;
return move;
}

vector<int> PseudoTonga::move(int row, int col)
{
do_move(row, col, svr_color);
cout << "server: row = " << row << ", col = " << col << "; ";
vector<int> move;
int d = 3;
move = se.search_move(d);
do_move(move[0], move[1], my_color);
cout << "player: row = " << move[0] << ", col = " << move[1] << "; ";
cout << "leaf count is " << leaf_cnt << endl;
return move;
}

void PseudoTonga::do_move(int row, int col, int color)
{
se.do_move(row, col, color);
}.........................................................

int main()
{
PseudoTonga pt;
pt.init(6, 2, 2);
pt.move(2,4);
return 0;
}