X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=21cd34a2997812998b828901cbb575f0007afb4d;hp=2fd0cadaaadf86c1cdd463c4dd8cb33f3275e97d;hb=dfd030b67af4e651a73232ab15182fe669909ef1;hpb=b3a0b389d279dacd70fea429088122d02362d14a
diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 2fd0cada..21cd34a2 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -1,7 +1,7 @@
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -17,6 +17,7 @@
along with this program. If not, see .
*/
+#include
#include
#include
@@ -24,26 +25,23 @@
#include "bitcount.h"
#include "rkiss.h"
-// Global bitboards definitions with static storage duration are
-// automatically set to zero before enter main().
-Bitboard RMask[64];
-Bitboard RMult[64];
+Bitboard RMasks[64];
+Bitboard RMagics[64];
Bitboard* RAttacks[64];
-int RShift[64];
+int RShifts[64];
-Bitboard BMask[64];
-Bitboard BMult[64];
+Bitboard BMasks[64];
+Bitboard BMagics[64];
Bitboard* BAttacks[64];
-int BShift[64];
+int BShifts[64];
Bitboard SetMaskBB[65];
Bitboard ClearMaskBB[65];
-Bitboard SquaresByColorBB[2];
Bitboard FileBB[8];
Bitboard RankBB[8];
-Bitboard NeighboringFilesBB[8];
-Bitboard ThisAndNeighboringFilesBB[8];
+Bitboard AdjacentFilesBB[8];
+Bitboard ThisAndAdjacentFilesBB[8];
Bitboard InFrontBB[2][8];
Bitboard StepAttacksBB[16][64];
Bitboard BetweenBB[64][64];
@@ -51,22 +49,23 @@ Bitboard SquaresInFrontMask[2][64];
Bitboard PassedPawnMask[2][64];
Bitboard AttackSpanMask[2][64];
-Bitboard BishopPseudoAttacks[64];
-Bitboard RookPseudoAttacks[64];
-Bitboard QueenPseudoAttacks[64];
+Bitboard PseudoAttacks[6][64];
uint8_t BitCount8Bit[256];
+int SquareDistance[64][64];
namespace {
CACHE_LINE_ALIGNMENT
int BSFTable[64];
- Bitboard RAttacksTable[0x19000];
- Bitboard BAttacksTable[0x1480];
+ Bitboard RTable[0x19000]; // Storage space for rook attacks
+ Bitboard BTable[0x1480]; // Storage space for bishop attacks
- void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
- Bitboard mask[], int shift[], Square delta[]);
+ typedef unsigned (Fn)(Square, Bitboard);
+
+ void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], int shifts[], Square deltas[], Fn get_index);
}
@@ -149,13 +148,13 @@ Square pop_1st_bit(Bitboard* bb) {
#endif // !defined(USE_BSFQ)
-/// init_bitboards() initializes various bitboard arrays. It is called during
+/// bitboards_init() initializes various bitboard arrays. It is called during
/// program initialization.
-void init_bitboards() {
+void bitboards_init() {
- SquaresByColorBB[DARK] = 0xAA55AA55AA55AA55ULL;
- SquaresByColorBB[LIGHT] = ~SquaresByColorBB[DARK];
+ for (Bitboard b = 0; b < 256; b++)
+ BitCount8Bit[b] = (uint8_t)popcount(b);
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
@@ -163,7 +162,7 @@ void init_bitboards() {
ClearMaskBB[s] = ~SetMaskBB[s];
}
- ClearMaskBB[SQ_NONE] = ~EmptyBoardBB;
+ ClearMaskBB[SQ_NONE] = ~0ULL;
FileBB[FILE_A] = FileABB;
RankBB[RANK_1] = Rank1BB;
@@ -176,8 +175,8 @@ void init_bitboards() {
for (int f = FILE_A; f <= FILE_H; f++)
{
- NeighboringFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
- ThisAndNeighboringFilesBB[f] = FileBB[f] | NeighboringFilesBB[f];
+ AdjacentFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
+ ThisAndAdjacentFilesBB[f] = FileBB[f] | AdjacentFilesBB[f];
}
for (int rw = RANK_7, rb = RANK_2; rw >= RANK_1; rw--, rb++)
@@ -190,20 +189,21 @@ void init_bitboards() {
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
SquaresInFrontMask[c][s] = in_front_bb(c, s) & file_bb(s);
- PassedPawnMask[c][s] = in_front_bb(c, s) & this_and_neighboring_files_bb(s);
- AttackSpanMask[c][s] = in_front_bb(c, s) & neighboring_files_bb(s);
+ PassedPawnMask[c][s] = in_front_bb(c, s) & this_and_adjacent_files_bb(file_of(s));
+ AttackSpanMask[c][s] = in_front_bb(c, s) & adjacent_files_bb(file_of(s));
}
- for (Bitboard b = 0; b < 256; b++)
- BitCount8Bit[b] = (uint8_t)count_1s(b);
+ for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
+ for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
+ SquareDistance[s1][s2] = std::max(file_distance(s1, s2), rank_distance(s1, s2));
for (int i = 0; i < 64; i++)
- if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
+ if (!Is64Bit) // Matt Taylor's folding trick for 32 bit systems
{
Bitboard b = 1ULL << i;
b ^= b - 1;
b ^= b >> 32;
- BSFTable[uint32_t(b * 0x783A9B23) >> 26] = i;
+ BSFTable[(uint32_t)(b * 0x783A9B23) >> 26] = i;
}
else
BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
@@ -222,79 +222,53 @@ void init_bitboards() {
set_bit(&StepAttacksBB[make_piece(c, pt)][s], to);
}
- Square RDelta[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
- Square BDelta[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
+ Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
+ Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
- init_sliding_attacks(BMult, BAttacks, BAttacksTable, BMask, BShift, BDelta);
- init_sliding_attacks(RMult, RAttacks, RAttacksTable, RMask, RShift, RDelta);
+ init_magics(RTable, RAttacks, RMagics, RMasks, RShifts, RDeltas, r_index);
+ init_magics(BTable, BAttacks, BMagics, BMasks, BShifts, BDeltas, b_index);
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
- BishopPseudoAttacks[s] = bishop_attacks_bb(s, EmptyBoardBB);
- RookPseudoAttacks[s] = rook_attacks_bb(s, EmptyBoardBB);
- QueenPseudoAttacks[s] = queen_attacks_bb(s, EmptyBoardBB);
+ PseudoAttacks[BISHOP][s] = bishop_attacks_bb(s, 0);
+ PseudoAttacks[ROOK][s] = rook_attacks_bb(s, 0);
+ PseudoAttacks[QUEEN][s] = PseudoAttacks[BISHOP][s] | PseudoAttacks[ROOK][s];
}
for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
- if (bit_is_set(QueenPseudoAttacks[s1], s2))
+ if (bit_is_set(PseudoAttacks[QUEEN][s1], s2))
{
- int f = file_distance(s1, s2);
- int r = rank_distance(s1, s2);
-
- Square d = (s2 - s1) / Max(f, r);
+ Square delta = (s2 - s1) / square_distance(s1, s2);
- for (Square s3 = s1 + d; s3 != s2; s3 += d)
- set_bit(&BetweenBB[s1][s2], s3);
+ for (Square s = s1 + delta; s != s2; s += delta)
+ set_bit(&BetweenBB[s1][s2], s);
}
}
namespace {
- Bitboard submask(Bitboard mask, int key) {
+ Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) {
- Bitboard b, subMask = 0;
- int bitProbe = 1;
-
- // Extract an unique submask out of a mask according to the given key
- while (mask)
- {
- b = mask & -mask;
- mask ^= b;
-
- if (key & bitProbe)
- subMask |= b;
-
- bitProbe <<= 1;
- }
- return subMask;
- }
-
- Bitboard sliding_attacks(Square sq, Bitboard occupied, Square delta[], Bitboard excluded) {
-
- Bitboard attacks = 0;
+ Bitboard attack = 0;
for (int i = 0; i < 4; i++)
- {
- Square s = sq + delta[i];
-
- while ( square_is_ok(s)
- && square_distance(s, s - delta[i]) == 1
- && !bit_is_set(excluded, s))
+ for (Square s = sq + deltas[i];
+ square_is_ok(s) && square_distance(s, s - deltas[i]) == 1;
+ s += deltas[i])
{
- set_bit(&attacks, s);
+ set_bit(&attack, s);
if (bit_is_set(occupied, s))
break;
-
- s += delta[i];
}
- }
- return attacks;
+
+ return attack;
}
- Bitboard pick_magic(Bitboard mask, RKISS& rk, int booster) {
+
+ Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) {
Bitboard magic;
@@ -315,51 +289,73 @@ namespace {
}
}
- void init_sliding_attacks(Bitboard magic[], Bitboard* attack[], Bitboard attTable[],
- Bitboard mask[], int shift[], Square delta[]) {
- const int MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 },
- { 1059, 3608, 605, 3234, 3326, 38, 2029, 3043 } };
+ // init_magics() computes all rook and bishop attacks at startup. Magic
+ // bitboards are used to look up attacks of sliding pieces. As a reference see
+ // chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
+ // use the so called "fancy" approach.
+
+ void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], int shifts[], Square deltas[], Fn get_index) {
+
+ int MagicBoosters[][8] = { { 3191, 2184, 1310, 3618, 2091, 1308, 2452, 3996 },
+ { 1059, 3608, 605, 3234, 3326, 38, 2029, 3043 } };
RKISS rk;
- Bitboard occupancy[4096], reference[4096], excluded;
- int key, maxKey, index, booster, offset = 0;
+ Bitboard occupancy[4096], reference[4096], edges, b;
+ int i, size, booster;
+
+ // attacks[s] is a pointer to the beginning of the attacks table for square 's'
+ attacks[SQ_A1] = table;
for (Square s = SQ_A1; s <= SQ_H8; s++)
{
- excluded = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));
-
- attack[s] = &attTable[offset];
- mask[s] = sliding_attacks(s, EmptyBoardBB, delta, excluded);
- shift[s] = (CpuIs64Bit ? 64 : 32) - count_1s(mask[s]);
+ // Board edges are not considered in the relevant occupancies
+ edges = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));
+
+ // Given a square 's', the mask is the bitboard of sliding attacks from
+ // 's' computed on an empty board. The index must be big enough to contain
+ // all the attacks for each possible subset of the mask and so is 2 power
+ // the number of 1s of the mask. Hence we deduce the size of the shift to
+ // apply to the 64 or 32 bits word to get the index.
+ masks[s] = sliding_attack(deltas, s, 0) & ~edges;
+ shifts[s] = (Is64Bit ? 64 : 32) - popcount(masks[s]);
+
+ // Use Carry-Rippler trick to enumerate all subsets of masks[s] and
+ // store the corresponding sliding attack bitboard in reference[].
+ b = size = 0;
+ do {
+ occupancy[size] = b;
+ reference[size++] = sliding_attack(deltas, s, b);
+ b = (b - masks[s]) & masks[s];
+ } while (b);
- maxKey = 1 << count_1s(mask[s]);
- offset += maxKey;
- booster = MagicBoosters[CpuIs64Bit][square_rank(s)];
+ // Set the offset for the table of the next square. We have individual
+ // table sizes for each square with "Fancy Magic Bitboards".
+ if (s < SQ_H8)
+ attacks[s + 1] = attacks[s] + size;
- // First compute occupancy and attacks for square 's'
- for (key = 0; key < maxKey; key++)
- {
- occupancy[key] = submask(mask[s], key);
- reference[key] = sliding_attacks(s, occupancy[key], delta, EmptyBoardBB);
- }
+ booster = MagicBoosters[Is64Bit][rank_of(s)];
- // Then find a possible magic and the corresponding attacks
+ // Find a magic for square 's' picking up an (almost) random number
+ // until we find the one that passes the verification test.
do {
- magic[s] = pick_magic(mask[s], rk, booster);
- memset(attack[s], 0, maxKey * sizeof(Bitboard));
-
- for (key = 0; key < maxKey; key++)
+ magics[s] = pick_random(masks[s], rk, booster);
+ memset(attacks[s], 0, size * sizeof(Bitboard));
+
+ // A good magic must map every possible occupancy to an index that
+ // looks up the correct sliding attack in the attacks[s] database.
+ // Note that we build up the database for square 's' as a side
+ // effect of verifying the magic.
+ for (i = 0; i < size; i++)
{
- index = CpuIs64Bit ? unsigned((occupancy[key] * magic[s]) >> shift[s])
- : unsigned(occupancy[key] * magic[s] ^ (occupancy[key] >> 32) * (magic[s] >> 32)) >> shift[s];
-
- if (!attack[s][index])
- attack[s][index] = reference[key];
+ Bitboard& attack = attacks[s][get_index(s, occupancy[i])];
- else if (attack[s][index] != reference[key])
+ if (attack && attack != reference[i])
break;
+
+ attack = reference[i];
}
- } while (key != maxKey);
+ } while (i != size);
}
}
}