othello-ai/PVS_Endgame.h at master · rodrigozhou/othello-ai · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
#ifndef PVS_Endgame_H
#define PVS_Endgame_H

#include <algorithm>
#include <vector>

#include "Board.h"
#include "Score.h"

using namespace std;

struct PVS_Endgame : Strategy {
    const static int cnt_tiles = Board::n * Board::n;
    const static int MAX_DEPTH = 7;
    const static int MAX_DEPTH_ENDGAME = 16;
    const static int MAX_SHALLOW_DEPTH = 2;

    double shallow_search(const Board &b, int player, int depth = 0,
            double alpha = -INF, double beta = INF) {
        if (depth >= MAX_SHALLOW_DEPTH)
            return score(b, player);
        Board newb;
        bool has_empty = false;
        double ret = -INF;
        for (int i = 0; i < b.n; i++) {
            for (int j = 0; j < b.n; j++) {
                if (b.is_empty(i, j))
                    has_empty = true;
                if (b.is_valid_move(player, i, j)) {
                    newb = b.make_move(player, i, j);
                    double aux = -shallow_search(newb, player ^ 1, depth + 1, -beta, -alpha);
                    ret = max(ret, aux);
                    alpha = max(alpha, aux);
                    if (alpha >= beta)
                        return alpha;
                }
            }
        }
        if (ret == -INF && has_empty)
            return -shallow_search(b, player ^ 1, depth + 1, -beta, -alpha);
        return ret;
    }

    int dfs_endgame(const Board &b, int player, int depth = 0,
            int alpha = -INF, int beta = INF) {
        if (depth >= MAX_DEPTH_ENDGAME)
            return b.cnt[player] - b.cnt[player^1];
        Board newb;
        bool has_empty = false;
        int ret = -INF;
        bool first_child = true;
        for (int i = 0; i < b.n; i++) {
            for (int j = 0; j < b.n; j++) {
                if (b.is_empty(i, j))
                    has_empty = true;
                if (b.is_valid_move(player, i, j)) {
                    newb = b.make_move(player, i, j);
                    int val;
                    if (!first_child) {
                        val = -dfs_endgame(newb, player ^ 1, depth + 1, -alpha - 1, -alpha);
                        if (alpha < val && val < beta) // Check for failure.
                            val = -dfs_endgame(newb, player ^ 1, depth + 1, -beta, -val);
                    }
                    else {
                        val = -dfs_endgame(newb, player ^ 1, depth + 1, -beta, -alpha);
                        first_child = false;
                    }
                    alpha = max(alpha, val);
                    ret = max(ret, val);
                    if (alpha >= beta)
                        return alpha;
                }
            }
        }
        if (ret == -INF && has_empty)
            return -dfs_endgame(b, player ^ 1, depth + 1, -beta, -alpha);
        return ret;
    }

    double dfs(const Board &b, int player, int depth = 0,
            double alpha = -INF, double beta = INF) {
        if (depth >= MAX_DEPTH)
            return score(b, player);
        Board newb;
        bool has_empty = false, first_child = true;
        double ret = -INF;
        for (int i = 0; i < b.n; i++) {
            for (int j = 0; j < b.n; j++) {
                if (b.is_empty(i, j))
                    has_empty = true;
                if (b.is_valid_move(player, i, j)) {
                    newb = b.make_move(player, i, j);
                    double val;
                    if (!first_child) {
                        val = -dfs(newb, player ^ 1, depth + 1, -alpha - 1, -alpha);
                        if (alpha < val && val < beta) // Check for failure.
                            val = -dfs(newb, player ^ 1, depth + 1, -beta, -val);
                    }
                    else {
                        val = -dfs(newb, player ^ 1, depth + 1, -beta, -alpha);
                        first_child = false;
                    }
                    alpha = max(alpha, val);
                    ret = max(ret, val);
                    if (alpha >= beta)
                        return alpha;
                }
            }
        }
        if (ret == -INF && has_empty)
            return -dfs(b, player ^ 1, depth + 1, -beta, -alpha);
        return ret;
    }

    pii get_next_move(const Board &b, int player) {
        vector< pair<double, pii> > pq;
        pii ret = mp(-1, -1);
        Board newb;
        double best = -INF;
        bool endgame = cnt_tiles - b.cnt[0] - b.cnt[1] <= MAX_DEPTH_ENDGAME;
        for (int i = 0; i < b.n; i++) {
            for (int j = 0; j < b.n; j++) {
                if (b.is_valid_move(player, i, j)) {
                    newb = b.make_move(player, i, j);
                    if (!endgame) {
                        pq.push_back(mp(-shallow_search(newb, player ^ 1, 0, -INF, -best),
                                    mp(i, j)));
                    } else {
                        int aux = -dfs_endgame(newb, player ^ 1, 0, -INF, -best);
                        if (aux > best) {
                            best = aux;
                            ret = mp(i, j);
                        }
                    }
                }
            }
        }

        if (!endgame) {
            sort(pq.begin(), pq.end());
            reverse(pq.begin(), pq.end());
            for (int i = 0; i < (int) pq.size(); i++) {
                newb = b.make_move(player, pq[i].second.first, pq[i].second.second);
                double aux = -dfs(newb, player ^ 1, 0, -INF, -best);
                if (aux > best) {
                    best = aux;
                    ret = pq[i].second;
                }
            }
        }

        return ret;
    }

};

#endif // PVS_Endgame_H