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
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
|
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
// TODO: make magic bitboards use diffrent shift for each magic number (maybe)
static int popcount(uint64_t b) { return __builtin_popcountll(b); }
static uint64_t computeRookMask(int sq) {
uint64_t mask = 0;
int r = sq / 8, f = sq % 8;
for (int i = r + 1; i < 7; i++)
mask |= 1ULL << (i * 8 + f);
for (int i = r - 1; i > 0; i--)
mask |= 1ULL << (i * 8 + f);
for (int j = f + 1; j < 7; j++)
mask |= 1ULL << (r * 8 + j);
for (int j = f - 1; j > 0; j--)
mask |= 1ULL << (r * 8 + j);
return mask;
}
static uint64_t computeBishopMask(int sq) {
uint64_t mask = 0;
int r = sq / 8, f = sq % 8;
for (int i = r + 1, j = f + 1; i < 7 && j < 7; i++, j++)
mask |= 1ULL << (i * 8 + j);
for (int i = r + 1, j = f - 1; i < 7 && j > 0; i++, j--)
mask |= 1ULL << (i * 8 + j);
for (int i = r - 1, j = f + 1; i > 0 && j < 7; i--, j++)
mask |= 1ULL << (i * 8 + j);
for (int i = r - 1, j = f - 1; i > 0 && j > 0; i--, j--)
mask |= 1ULL << (i * 8 + j);
return mask;
}
static uint64_t computeRookAttacks(int sq, uint64_t occ) {
uint64_t att = 0;
int r = sq / 8, f = sq % 8;
for (int i = r + 1; i < 8; i++) {
att |= 1ULL << (i * 8 + f);
if (occ & (1ULL << (i * 8 + f)))
break;
}
for (int i = r - 1; i >= 0; i--) {
att |= 1ULL << (i * 8 + f);
if (occ & (1ULL << (i * 8 + f)))
break;
}
for (int j = f + 1; j < 8; j++) {
att |= 1ULL << (r * 8 + j);
if (occ & (1ULL << (r * 8 + j)))
break;
}
for (int j = f - 1; j >= 0; j--) {
att |= 1ULL << (r * 8 + j);
if (occ & (1ULL << (r * 8 + j)))
break;
}
return att;
}
static uint64_t computeBishopAttacks(int sq, uint64_t occ) {
uint64_t att = 0;
int r = sq / 8, f = sq % 8;
for (int i = r + 1, j = f + 1; i < 8 && j < 8; i++, j++) {
att |= 1ULL << (i * 8 + j);
if (occ & (1ULL << (i * 8 + j)))
break;
}
for (int i = r + 1, j = f - 1; i < 8 && j >= 0; i++, j--) {
att |= 1ULL << (i * 8 + j);
if (occ & (1ULL << (i * 8 + j)))
break;
}
for (int i = r - 1, j = f + 1; i >= 0 && j < 8; i--, j++) {
att |= 1ULL << (i * 8 + j);
if (occ & (1ULL << (i * 8 + j)))
break;
}
for (int i = r - 1, j = f - 1; i >= 0 && j >= 0; i--, j--) {
att |= 1ULL << (i * 8 + j);
if (occ & (1ULL << (i * 8 + j)))
break;
}
return att;
}
static uint64_t mapSquaresToMask(uint64_t index, uint64_t mask) {
uint64_t result = 0;
int bits = __builtin_popcountll(mask);
for (int i = 0; i < bits; i++) {
int sq = __builtin_ctzll(mask);
mask &= mask - 1;
if (index & (1ULL << i))
result |= (1ULL << sq);
}
return result;
}
static int findMagic(uint64_t mask, uint64_t (*attackFn)(int, uint64_t), int sq,
int shift, uint64_t *outMagic) {
int nbits = popcount(mask);
uint64_t nocc = 1ULL << nbits;
uint64_t *occs = malloc(nocc * sizeof(uint64_t));
uint64_t *atts = malloc(nocc * sizeof(uint64_t));
for (uint64_t i = 0; i < nocc; i++) {
occs[i] = mapSquaresToMask(i, mask);
atts[i] = attackFn(sq, occs[i]);
}
uint64_t tableSize = 1ULL << (64 - shift);
uint64_t *table = malloc(tableSize * sizeof(uint64_t));
uint64_t *epoch = calloc(tableSize, sizeof(uint64_t));
uint64_t cnt = 0;
for (unsigned long long attempt = 0; attempt < 10000000000ULL; attempt++) {
uint64_t magic;
do {
magic =
((uint64_t)rand() << 32 | rand()) & ((uint64_t)rand() << 32 | rand());
} while (popcount((mask * magic) & 0xFF00000000000000ULL) < 6);
cnt++;
int ok = 1;
for (uint64_t i = 0; i < nocc; i++) {
uint64_t idx = (occs[i] * magic) >> shift;
if (epoch[idx] < cnt) {
epoch[idx] = cnt;
table[idx] = atts[i];
} else if (table[idx] != atts[i]) {
ok = 0;
break;
}
}
if (ok) {
*outMagic = magic;
free(occs);
free(atts);
free(table);
free(epoch);
return 1;
}
}
free(occs);
free(atts);
free(table);
free(epoch);
return 0;
}
int main(int argc, char *argv[]) {
int shift = 52;
if (argc > 1) {
shift = atoi(argv[1]);
if (shift < 32 || shift > 63) {
fprintf(stderr, "Usage: %s [shift] (32..63, default 52)\n", argv[0]);
return 1;
}
}
srand(time(NULL));
uint64_t rookMags[64], bishopMags[64];
uint64_t rookMasks[64], bishopMasks[64];
fprintf(stderr,
"Finding per-square rook magics (shift %d, table size %llu)...\n",
shift, (unsigned long long)(1ULL << (64 - shift)));
for (int sq = 0; sq < 64; sq++) {
rookMasks[sq] = computeRookMask(sq);
if (!findMagic(rookMasks[sq], computeRookAttacks, sq, shift,
&rookMags[sq])) {
fprintf(stderr, "FAILED to find rook magic for square %d\n", sq);
return 1;
}
fprintf(stderr, " sq %2d: %d bits, magic 0x%016llx\n", sq,
popcount(rookMasks[sq]), (unsigned long long)rookMags[sq]);
}
fprintf(stderr, "\nFinding per-square bishop magics (shift %d)...\n", shift);
for (int sq = 0; sq < 64; sq++) {
bishopMasks[sq] = computeBishopMask(sq);
if (!findMagic(bishopMasks[sq], computeBishopAttacks, sq, shift,
&bishopMags[sq])) {
fprintf(stderr, "FAILED to find bishop magic for square %d\n", sq);
return 1;
}
fprintf(stderr, " sq %2d: %d bits, magic 0x%016llx\n", sq,
popcount(bishopMasks[sq]), (unsigned long long)bishopMags[sq]);
}
fprintf(stderr, "\nDone! Writing magics.txt\n");
FILE *f = fopen("magics.txt", "w");
if (!f) {
fprintf(stderr, "Cannot open magics.txt\n");
return 1;
}
fprintf(f, "// shift = %d\n", shift);
fprintf(f, "constexpr int MAGIC_SHIFT = %d;\n\n", shift);
fprintf(f, "constexpr std::array<uint64_t, 64> rookMagics = {\n");
for (int i = 0; i < 64; i++) {
fprintf(f, " 0x%016llxULL%c // %c%d\n", (unsigned long long)rookMags[i],
i < 63 ? ',' : ' ', 'a' + i % 8, i / 8 + 1);
}
fprintf(f, "};\n\n");
fprintf(f, "constexpr std::array<uint64_t, 64> bishopMagics = {\n");
for (int i = 0; i < 64; i++) {
fprintf(f, " 0x%016llxULL%c // %c%d\n",
(unsigned long long)bishopMags[i], i < 63 ? ',' : ' ', 'a' + i % 8,
i / 8 + 1);
}
fprintf(f, "};\n");
fclose(f);
return 0;
}
|
