mirror of
https://github.com/peterosterlund2/droidfish.git
synced 2025-01-08 08:17:01 +01:00
352 lines
11 KiB
C++
352 lines
11 KiB
C++
/*
|
|
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
|
|
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
|
|
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
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
Stockfish is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <algorithm>
|
|
#include <cstring>
|
|
#include <iostream>
|
|
|
|
#include "bitboard.h"
|
|
#include "bitcount.h"
|
|
#include "misc.h"
|
|
#include "rkiss.h"
|
|
|
|
CACHE_LINE_ALIGNMENT
|
|
|
|
Bitboard RMasks[64];
|
|
Bitboard RMagics[64];
|
|
Bitboard* RAttacks[64];
|
|
unsigned RShifts[64];
|
|
|
|
Bitboard BMasks[64];
|
|
Bitboard BMagics[64];
|
|
Bitboard* BAttacks[64];
|
|
unsigned BShifts[64];
|
|
|
|
Bitboard SquareBB[64];
|
|
Bitboard FileBB[8];
|
|
Bitboard RankBB[8];
|
|
Bitboard AdjacentFilesBB[8];
|
|
Bitboard ThisAndAdjacentFilesBB[8];
|
|
Bitboard InFrontBB[2][8];
|
|
Bitboard StepAttacksBB[16][64];
|
|
Bitboard BetweenBB[64][64];
|
|
Bitboard DistanceRingsBB[64][8];
|
|
Bitboard ForwardBB[2][64];
|
|
Bitboard PassedPawnMask[2][64];
|
|
Bitboard AttackSpanMask[2][64];
|
|
Bitboard PseudoAttacks[6][64];
|
|
|
|
int SquareDistance[64][64];
|
|
|
|
namespace {
|
|
|
|
// De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
|
|
const uint64_t DeBruijn_64 = 0x218A392CD3D5DBFULL;
|
|
const uint32_t DeBruijn_32 = 0x783A9B23;
|
|
|
|
CACHE_LINE_ALIGNMENT
|
|
|
|
int MS1BTable[256];
|
|
Square BSFTable[64];
|
|
Bitboard RTable[0x19000]; // Storage space for rook attacks
|
|
Bitboard BTable[0x1480]; // Storage space for bishop attacks
|
|
uint8_t BitCount8Bit[256];
|
|
|
|
typedef unsigned (Fn)(Square, Bitboard);
|
|
|
|
void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
|
|
Bitboard masks[], unsigned shifts[], Square deltas[], Fn index);
|
|
|
|
FORCE_INLINE unsigned bsf_index(Bitboard b) {
|
|
|
|
if (Is64Bit)
|
|
return ((b & -b) * DeBruijn_64) >> 58;
|
|
|
|
// Use Matt Taylor's folding trick for 32 bit systems
|
|
b ^= (b - 1);
|
|
return ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn_32) >> 26;
|
|
}
|
|
}
|
|
|
|
/// lsb()/msb() finds the least/most significant bit in a nonzero bitboard.
|
|
/// pop_lsb() finds and clears the least significant bit in a nonzero bitboard.
|
|
|
|
#if !defined(USE_BSFQ)
|
|
|
|
Square lsb(Bitboard b) { return BSFTable[bsf_index(b)]; }
|
|
|
|
Square pop_lsb(Bitboard* b) {
|
|
|
|
Bitboard bb = *b;
|
|
*b = bb & (bb - 1);
|
|
return BSFTable[bsf_index(bb)];
|
|
}
|
|
|
|
Square msb(Bitboard b) {
|
|
|
|
unsigned b32;
|
|
int result = 0;
|
|
|
|
if (b > 0xFFFFFFFF)
|
|
{
|
|
b >>= 32;
|
|
result = 32;
|
|
}
|
|
|
|
b32 = unsigned(b);
|
|
|
|
if (b32 > 0xFFFF)
|
|
{
|
|
b32 >>= 16;
|
|
result += 16;
|
|
}
|
|
|
|
if (b32 > 0xFF)
|
|
{
|
|
b32 >>= 8;
|
|
result += 8;
|
|
}
|
|
|
|
return (Square)(result + MS1BTable[b32]);
|
|
}
|
|
|
|
#endif // !defined(USE_BSFQ)
|
|
|
|
|
|
/// Bitboards::print() prints a bitboard in an easily readable format to the
|
|
/// standard output. This is sometimes useful for debugging.
|
|
|
|
void Bitboards::print(Bitboard b) {
|
|
|
|
sync_cout;
|
|
|
|
for (Rank rank = RANK_8; rank >= RANK_1; rank--)
|
|
{
|
|
std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
|
|
|
|
for (File file = FILE_A; file <= FILE_H; file++)
|
|
std::cout << "| " << (b & (file | rank) ? "X " : " ");
|
|
|
|
std::cout << "|\n";
|
|
}
|
|
std::cout << "+---+---+---+---+---+---+---+---+" << sync_endl;
|
|
}
|
|
|
|
|
|
/// Bitboards::init() initializes various bitboard arrays. It is called during
|
|
/// program initialization.
|
|
|
|
void Bitboards::init() {
|
|
|
|
for (int k = 0, i = 0; i < 8; i++)
|
|
while (k < (2 << i))
|
|
MS1BTable[k++] = i;
|
|
|
|
for (int i = 0; i < 64; i++)
|
|
BSFTable[bsf_index(1ULL << i)] = Square(i);
|
|
|
|
for (Bitboard b = 0; b < 256; b++)
|
|
BitCount8Bit[b] = (uint8_t)popcount<Max15>(b);
|
|
|
|
for (Square s = SQ_A1; s <= SQ_H8; s++)
|
|
SquareBB[s] = 1ULL << s;
|
|
|
|
FileBB[FILE_A] = FileABB;
|
|
RankBB[RANK_1] = Rank1BB;
|
|
|
|
for (int i = 1; i < 8; i++)
|
|
{
|
|
FileBB[i] = FileBB[i - 1] << 1;
|
|
RankBB[i] = RankBB[i - 1] << 8;
|
|
}
|
|
|
|
for (File f = FILE_A; f <= FILE_H; f++)
|
|
{
|
|
AdjacentFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
|
|
ThisAndAdjacentFilesBB[f] = FileBB[f] | AdjacentFilesBB[f];
|
|
}
|
|
|
|
for (Rank r = RANK_1; r < RANK_8; r++)
|
|
InFrontBB[WHITE][r] = ~(InFrontBB[BLACK][r + 1] = InFrontBB[BLACK][r] | RankBB[r]);
|
|
|
|
for (Color c = WHITE; c <= BLACK; c++)
|
|
for (Square s = SQ_A1; s <= SQ_H8; s++)
|
|
{
|
|
ForwardBB[c][s] = InFrontBB[c][rank_of(s)] & FileBB[file_of(s)];
|
|
PassedPawnMask[c][s] = InFrontBB[c][rank_of(s)] & ThisAndAdjacentFilesBB[file_of(s)];
|
|
AttackSpanMask[c][s] = InFrontBB[c][rank_of(s)] & AdjacentFilesBB[file_of(s)];
|
|
}
|
|
|
|
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 (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
|
|
for (int d = 1; d < 8; d++)
|
|
for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
|
|
if (SquareDistance[s1][s2] == d)
|
|
DistanceRingsBB[s1][d - 1] |= s2;
|
|
|
|
int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
|
|
{}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };
|
|
|
|
for (Color c = WHITE; c <= BLACK; c++)
|
|
for (PieceType pt = PAWN; pt <= KING; pt++)
|
|
for (Square s = SQ_A1; s <= SQ_H8; s++)
|
|
for (int k = 0; steps[pt][k]; k++)
|
|
{
|
|
Square to = s + Square(c == WHITE ? steps[pt][k] : -steps[pt][k]);
|
|
|
|
if (is_ok(to) && square_distance(s, to) < 3)
|
|
StepAttacksBB[make_piece(c, pt)][s] |= to;
|
|
}
|
|
|
|
Square RDeltas[] = { DELTA_N, DELTA_E, DELTA_S, DELTA_W };
|
|
Square BDeltas[] = { DELTA_NE, DELTA_SE, DELTA_SW, DELTA_NW };
|
|
|
|
init_magics(RTable, RAttacks, RMagics, RMasks, RShifts, RDeltas, magic_index<ROOK>);
|
|
init_magics(BTable, BAttacks, BMagics, BMasks, BShifts, BDeltas, magic_index<BISHOP>);
|
|
|
|
for (Square s = SQ_A1; s <= SQ_H8; s++)
|
|
{
|
|
PseudoAttacks[QUEEN][s] = PseudoAttacks[BISHOP][s] = attacks_bb<BISHOP>(s, 0);
|
|
PseudoAttacks[QUEEN][s] |= PseudoAttacks[ ROOK][s] = attacks_bb< ROOK>(s, 0);
|
|
}
|
|
|
|
for (Square s1 = SQ_A1; s1 <= SQ_H8; s1++)
|
|
for (Square s2 = SQ_A1; s2 <= SQ_H8; s2++)
|
|
if (PseudoAttacks[QUEEN][s1] & s2)
|
|
{
|
|
Square delta = (s2 - s1) / square_distance(s1, s2);
|
|
|
|
for (Square s = s1 + delta; s != s2; s += delta)
|
|
BetweenBB[s1][s2] |= s;
|
|
}
|
|
}
|
|
|
|
|
|
namespace {
|
|
|
|
Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) {
|
|
|
|
Bitboard attack = 0;
|
|
|
|
for (int i = 0; i < 4; i++)
|
|
for (Square s = sq + deltas[i];
|
|
is_ok(s) && square_distance(s, s - deltas[i]) == 1;
|
|
s += deltas[i])
|
|
{
|
|
attack |= s;
|
|
|
|
if (occupied & s)
|
|
break;
|
|
}
|
|
|
|
return attack;
|
|
}
|
|
|
|
|
|
Bitboard pick_random(RKISS& rk, int booster) {
|
|
|
|
// Values s1 and s2 are used to rotate the candidate magic of a
|
|
// quantity known to be the optimal to quickly find the magics.
|
|
int s1 = booster & 63, s2 = (booster >> 6) & 63;
|
|
|
|
Bitboard m = rk.rand<Bitboard>();
|
|
m = (m >> s1) | (m << (64 - s1));
|
|
m &= rk.rand<Bitboard>();
|
|
m = (m >> s2) | (m << (64 - s2));
|
|
return m & rk.rand<Bitboard>();
|
|
}
|
|
|
|
|
|
// 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[], unsigned shifts[], Square deltas[], Fn 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], 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++)
|
|
{
|
|
// 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<Max15>(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);
|
|
|
|
// 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;
|
|
|
|
booster = MagicBoosters[Is64Bit][rank_of(s)];
|
|
|
|
// Find a magic for square 's' picking up an (almost) random number
|
|
// until we find the one that passes the verification test.
|
|
do {
|
|
do magics[s] = pick_random(rk, booster);
|
|
while (BitCount8Bit[(magics[s] * masks[s]) >> 56] < 6);
|
|
|
|
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++)
|
|
{
|
|
Bitboard& attack = attacks[s][index(s, occupancy[i])];
|
|
|
|
if (attack && attack != reference[i])
|
|
break;
|
|
|
|
assert(reference[i] != 0);
|
|
|
|
attack = reference[i];
|
|
}
|
|
} while (i != size);
|
|
}
|
|
}
|
|
}
|