ChessEngine/eval.cpp at main · Kaushikj-7/ChessEngine · 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
#include "eval.h"
#include "bitboard.h"
#include <climits>

// Material weights
const int P_VAL = 100;
const int N_VAL = 320;
const int B_VAL = 330;
const int R_VAL = 500;
const int Q_VAL = 900;
const int K_VAL = 20000;

// Pawn: Encourage push, center control
const int pawn_pst[64] = {
    0,   0,   0,   0,   0,   0,   0,   0,
    5,  10,  10, -20, -20,  10,  10,   5,
    5,  -5, -10,   0,   0, -10,  -5,   5,
    0,   0,   0,  20,  20,   0,   0,   0,
    5,   5,  10,  25,  25,  10,   5,   5,
   10,  10,  20,  30,  30,  20,  10,  10,
   50,  50,  50,  50,  50,  50,  50,  50,
    0,   0,   0,   0,   0,   0,   0,   0
};

// Knight: Center squares good. Edges bad.
const int knight_pst[64] = {
   -50, -40, -30, -30, -30, -30, -40, -50,
   -40, -20,   0,   5,   5,   0, -20, -40,
   -30,   5,  10,  15,  15,  10,   5, -30,
   -30,   0,  15,  20,  20,  15,   0, -30,
   -30,   5,  15,  20,  20,  15,   5, -30,
   -30,   0,  10,  15,  15,  10,   0, -30,
   -40, -20,   0,   0,   0,   0, -20, -40,
   -50, -40, -30, -30, -30, -30, -40, -50
};

// Bishop: Good diagonals, avoid corners?
const int bishop_pst[64] = {
   -20, -10, -10, -10, -10, -10, -10, -20,
   -10,   5,   0,   0,   0,   0,   5, -10,
   -10,  10,  10,  10,  10,  10,  10, -10,
   -10,   0,  10,  10,  10,  10,   0, -10,
   -10,   5,   5,  10,  10,   5,   5, -10,
   -10,   0,   5,  10,  10,   5,   0, -10,
   -10,   0,   0,   0,   0,   0,   0, -10,
   -20, -10, -10, -10, -10, -10, -10, -20
};

// Rook: 7th rank, open files? (PST just encourages centralization slightly for now)
const int rook_pst[64] = {
    0,   0,   0,   5,   5,   0,   0,   0,
   -5,   0,   0,   0,   0,   0,   0,  -5,
   -5,   0,   0,   0,   0,   0,   0,  -5,
   -5,   0,   0,   0,   0,   0,   0,  -5,
   -5,   0,   0,   0,   0,   0,   0,  -5,
   -5,   0,   0,   0,   0,   0,   0,  -5,
    5,  10,  10,  10,  10,  10,  10,   5,
    0,   0,   0,   0,   0,   0,   0,   0
};

// Queen: Mobility (center)
const int queen_pst[64] = {
   -20, -10, -10, -5, -5, -10, -10, -20,
   -10,   0,   0,  0,  0,   0,   0, -10,
   -10,   0,   5,  5,  5,   5,   0, -10,
    -5,   0,   5,  5,  5,   5,   0,  -5,
     0,   0,   5,  5,  5,   5,   0,  -5,
   -10,   5,   5,  5,  5,   5,   0, -10,
   -10,   0,   5,  0,  0,   0,   0, -10,
   -20, -10, -10, -5, -5, -10, -10, -20
};

// King (Middle Game): Safety in corners (g1, b1)
const int king_pst[64] = {
    20,  30,  10,   0,   0,  10,  30,  20,
    20,  20,   0,   0,   0,   0,  20,  20,
   -10, -20, -20, -20, -20, -20, -20, -10,
   -20, -30, -30, -40, -40, -30, -30, -20,
   -30, -40, -40, -50, -50, -40, -40, -30,
   -30, -40, -40, -50, -50, -40, -40, -30,
   -30, -40, -40, -50, -50, -40, -40, -30,
   -30, -40, -40, -50, -50, -40, -40, -30
};

// Helper: Mirror square index for Black
// a1 (0) -> a8 (56).  Rank r -> 7-r.
int mirrorRef(int sq) {
    int r = sq / 8;
    int f = sq % 8;
    return (7 - r) * 8 + f;
}

int evaluatePieceFuncPST(int pcType, Bitboard bb, bool white) {
    int score = 0;
    const int* table = nullptr;
    int material = 0;

    switch(pcType) {
        case 0: table = pawn_pst; material = P_VAL; break; // Pawn
        case 1: table = knight_pst; material = N_VAL; break; // Knight
        case 2: table = bishop_pst; material = B_VAL; break; // Bishop
        case 3: table = rook_pst; material = R_VAL; break; // Rook
        case 4: table = queen_pst; material = Q_VAL; break; // Queen
        case 5: table = king_pst; material = K_VAL; break; // King
    }

    while (bb) {
        int sq = get_lsb(bb);
        int pstScore = 0;
        if (white) {
            pstScore = table[sq];
        } else {
            pstScore = table[mirrorRef(sq)];
        }
        score += material + pstScore;
        bb &= bb - 1;
    }
    return score;
}


int Evaluator::evaluate(const Board& board) {
    int score = 0;

    // White pieces (0-5)
    score += evaluatePieceFuncPST(0, board.pieces[WP], true);
    score += evaluatePieceFuncPST(1, board.pieces[WN], true);
    score += evaluatePieceFuncPST(2, board.pieces[WB], true);
    score += evaluatePieceFuncPST(3, board.pieces[WR], true);
    score += evaluatePieceFuncPST(4, board.pieces[WQ], true);
    score += evaluatePieceFuncPST(5, board.pieces[WK], true);

    // Black pieces (0-5)
    score -= evaluatePieceFuncPST(0, board.pieces[BP], false);
    score -= evaluatePieceFuncPST(1, board.pieces[BN], false);
    score -= evaluatePieceFuncPST(2, board.pieces[BB], false);
    score -= evaluatePieceFuncPST(3, board.pieces[BR], false);
    score -= evaluatePieceFuncPST(4, board.pieces[BQ], false);
    score -= evaluatePieceFuncPST(5, board.pieces[BK], false);

    return board.whiteToMove ? score : -score;
}