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BM123499 committed Apr 26, 2021
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191 changes: 89 additions & 102 deletions src/bitboard.cpp
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Expand Up @@ -18,7 +18,6 @@

#include <algorithm>
#include <bitset>
#include <array>

#include "bitboard.h"
#include "misc.h"
Expand All @@ -34,94 +33,93 @@ Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];

Magic< ROOK> RookMagics[SQUARE_NB];
Magic<BISHOP> BishopMagics[SQUARE_NB];

namespace {
using KnownMagicArray = std::array<KnownMagic, SQUARE_NB>;

// If using magic bitboards, it's possible to reduce the size of the
// attack table (~694 kB instead of 841 kB) by using specific offsets
// in the table for each piece, to allow overlaps wherever possible.
// We use magics and offsets originally found by Volker Annuss:
// www.talkchess.com/forum3/viewtopic.php?p=727500#p727500
constexpr KnownMagicArray KnownRookMagics = {
KnownMagic { 0x00280077ffebfffeu, 26304 }, KnownMagic { 0x2004010201097fffu, 35520 },
KnownMagic { 0x0010020010053fffu, 38592 }, KnownMagic { 0x0040040008004002u, 8026 },
KnownMagic { 0x7fd00441ffffd003u, 22196 }, KnownMagic { 0x4020008887dffffeu, 80870 },
KnownMagic { 0x004000888847ffffu, 76747 }, KnownMagic { 0x006800fbff75fffdu, 30400 },
KnownMagic { 0x000028010113ffffu, 11115 }, KnownMagic { 0x0020040201fcffffu, 18205 },
KnownMagic { 0x007fe80042ffffe8u, 53577 }, KnownMagic { 0x00001800217fffe8u, 62724 },
KnownMagic { 0x00001800073fffe8u, 34282 }, KnownMagic { 0x00001800e05fffe8u, 29196 },
KnownMagic { 0x00001800602fffe8u, 23806 }, KnownMagic { 0x000030002fffffa0u, 49481 },
KnownMagic { 0x00300018010bffffu, 2410 }, KnownMagic { 0x0003000c0085fffbu, 36498 },
KnownMagic { 0x0004000802010008u, 24478 }, KnownMagic { 0x0004002020020004u, 10074 },
KnownMagic { 0x0001002002002001u, 79315 }, KnownMagic { 0x0001001000801040u, 51779 },
KnownMagic { 0x0000004040008001u, 13586 }, KnownMagic { 0x0000006800cdfff4u, 19323 },
KnownMagic { 0x0040200010080010u, 70612 }, KnownMagic { 0x0000080010040010u, 83652 },
KnownMagic { 0x0004010008020008u, 63110 }, KnownMagic { 0x0000040020200200u, 34496 },
KnownMagic { 0x0002008010100100u, 84966 }, KnownMagic { 0x0000008020010020u, 54341 },
KnownMagic { 0x0000008020200040u, 60421 }, KnownMagic { 0x0000820020004020u, 86402 },
KnownMagic { 0x00fffd1800300030u, 50245 }, KnownMagic { 0x007fff7fbfd40020u, 76622 },
KnownMagic { 0x003fffbd00180018u, 84676 }, KnownMagic { 0x001fffde80180018u, 78757 },
KnownMagic { 0x000fffe0bfe80018u, 37346 }, KnownMagic { 0x0001000080202001u, 370 },
KnownMagic { 0x0003fffbff980180u, 42182 }, KnownMagic { 0x0001fffdff9000e0u, 45385 },
KnownMagic { 0x00fffefeebffd800u, 61659 }, KnownMagic { 0x007ffff7ffc01400u, 12790 },
KnownMagic { 0x003fffbfe4ffe800u, 16762 }, KnownMagic { 0x001ffff01fc03000u, 0 },
KnownMagic { 0x000fffe7f8bfe800u, 38380 }, KnownMagic { 0x0007ffdfdf3ff808u, 11098 },
KnownMagic { 0x0003fff85fffa804u, 21803 }, KnownMagic { 0x0001fffd75ffa802u, 39189 },
KnownMagic { 0x00ffffd7ffebffd8u, 58628 }, KnownMagic { 0x007fff75ff7fbfd8u, 44116 },
KnownMagic { 0x003fff863fbf7fd8u, 78357 }, KnownMagic { 0x001fffbfdfd7ffd8u, 44481 },
KnownMagic { 0x000ffff810280028u, 64134 }, KnownMagic { 0x0007ffd7f7feffd8u, 41759 },
KnownMagic { 0x0003fffc0c480048u, 1394 }, KnownMagic { 0x0001ffffafd7ffd8u, 40910 },
KnownMagic { 0x00ffffe4ffdfa3bau, 66516 }, KnownMagic { 0x007fffef7ff3d3dau, 3897 },
KnownMagic { 0x003fffbfdfeff7fau, 3930 }, KnownMagic { 0x001fffeff7fbfc22u, 72934 },
KnownMagic { 0x0000020408001001u, 72662 }, KnownMagic { 0x0007fffeffff77fdu, 56325 },
KnownMagic { 0x0003ffffbf7dfeecu, 66501 }, KnownMagic { 0x0001ffff9dffa333u, 14826 }
};

constexpr KnownMagicArray KnownBishopMagics = {
KnownMagic { 0x007fbfbfbfbfbfffu, 5378 }, KnownMagic { 0x0000a060401007fcu, 4093 },
KnownMagic { 0x0001004008020000u, 4314 }, KnownMagic { 0x0000806004000000u, 6587 },
KnownMagic { 0x0000100400000000u, 6491 }, KnownMagic { 0x000021c100b20000u, 6330 },
KnownMagic { 0x0000040041008000u, 5609 }, KnownMagic { 0x00000fb0203fff80u, 22236 },
KnownMagic { 0x0000040100401004u, 6106 }, KnownMagic { 0x0000020080200802u, 5625 },
KnownMagic { 0x0000004010202000u, 16785 }, KnownMagic { 0x0000008060040000u, 16817 },
KnownMagic { 0x0000004402000000u, 6842 }, KnownMagic { 0x0000000801008000u, 7003 },
KnownMagic { 0x000007efe0bfff80u, 4197 }, KnownMagic { 0x0000000820820020u, 7356 },
KnownMagic { 0x0000400080808080u, 4602 }, KnownMagic { 0x00021f0100400808u, 4538 },
KnownMagic { 0x00018000c06f3fffu, 29531 }, KnownMagic { 0x0000258200801000u, 45393 },
KnownMagic { 0x0000240080840000u, 12420 }, KnownMagic { 0x000018000c03fff8u, 15763 },
KnownMagic { 0x00000a5840208020u, 5050 }, KnownMagic { 0x0000020008208020u, 4346 },
KnownMagic { 0x0000804000810100u, 6074 }, KnownMagic { 0x0001011900802008u, 7866 },
KnownMagic { 0x0000804000810100u, 32139 }, KnownMagic { 0x000100403c0403ffu, 57673 },
KnownMagic { 0x00078402a8802000u, 55365 }, KnownMagic { 0x0000101000804400u, 15818 },
KnownMagic { 0x0000080800104100u, 5562 }, KnownMagic { 0x00004004c0082008u, 6390 },
KnownMagic { 0x0001010120008020u, 7930 }, KnownMagic { 0x000080809a004010u, 13329 },
KnownMagic { 0x0007fefe08810010u, 7170 }, KnownMagic { 0x0003ff0f833fc080u, 27267 },
KnownMagic { 0x007fe08019003042u, 53787 }, KnownMagic { 0x003fffefea003000u, 5097 },
KnownMagic { 0x0000101010002080u, 6643 }, KnownMagic { 0x0000802005080804u, 6138 },
KnownMagic { 0x0000808080a80040u, 7418 }, KnownMagic { 0x0000104100200040u, 7898 },
KnownMagic { 0x0003ffdf7f833fc0u, 42012 }, KnownMagic { 0x0000008840450020u, 57350 },
KnownMagic { 0x00007ffc80180030u, 22813 }, KnownMagic { 0x007fffdd80140028u, 56693 },
KnownMagic { 0x00020080200a0004u, 5818 }, KnownMagic { 0x0000101010100020u, 7098 },
KnownMagic { 0x0007ffdfc1805000u, 4451 }, KnownMagic { 0x0003ffefe0c02200u, 4709 },
KnownMagic { 0x0000000820806000u, 4794 }, KnownMagic { 0x0000000008403000u, 13364 },
KnownMagic { 0x0000000100202000u, 4570 }, KnownMagic { 0x0000004040802000u, 4282 },
KnownMagic { 0x0004010040100400u, 14964 }, KnownMagic { 0x00006020601803f4u, 4026 },
KnownMagic { 0x0003ffdfdfc28048u, 4826 }, KnownMagic { 0x0000000820820020u, 7354 },
KnownMagic { 0x0000000008208060u, 4848 }, KnownMagic { 0x0000000000808020u, 15946 },
KnownMagic { 0x0000000001002020u, 14932 }, KnownMagic { 0x0000000401002008u, 16588 },
KnownMagic { 0x0000004040404040u, 6905 }, KnownMagic { 0x007fff9fdf7ff813u, 16076 }
};

// If using PEXT indexing, do not use reduced table size.
Bitboard SlideAttackTable[HasPext ? 0x19000 + 0x1480 : 88772] {};
Bitboard SlideAttackTable[HasPext ? 0x19000 + 0x1480 : 88772] = {};

template<PieceType Pt>
void init_magics(Bitboard table[], Magic<Pt> magics[]);
void init_magics(Magic<Pt> magics[]);
}

// If using magic bitboards, it's possible to reduce the size of the
// attack table (~694 kB instead of 841 kB) by using specific offsets
// in the table for each piece, to allow overlaps wherever possible.
// We use magics and offsets originally found by Volker Annuss:
// www.talkchess.com/forum3/viewtopic.php?p=727500#p727500
#define sat SlideAttackTable

Magic< ROOK > RookMagics[SQUARE_NB] = {
{ 0x00280077ffebfffeULL, sat + 26304 }, { 0x2004010201097fffULL, sat + 35520 },
{ 0x0010020010053fffULL, sat + 38592 }, { 0x0040040008004002ULL, sat + 8026 },
{ 0x7fd00441ffffd003ULL, sat + 22196 }, { 0x4020008887dffffeULL, sat + 80870 },
{ 0x004000888847ffffULL, sat + 76747 }, { 0x006800fbff75fffdULL, sat + 30400 },
{ 0x000028010113ffffULL, sat + 11115 }, { 0x0020040201fcffffULL, sat + 18205 },
{ 0x007fe80042ffffe8ULL, sat + 53577 }, { 0x00001800217fffe8ULL, sat + 62724 },
{ 0x00001800073fffe8ULL, sat + 34282 }, { 0x00001800e05fffe8ULL, sat + 29196 },
{ 0x00001800602fffe8ULL, sat + 23806 }, { 0x000030002fffffa0ULL, sat + 49481 },
{ 0x00300018010bffffULL, sat + 2410 }, { 0x0003000c0085fffbULL, sat + 36498 },
{ 0x0004000802010008ULL, sat + 24478 }, { 0x0004002020020004ULL, sat + 10074 },
{ 0x0001002002002001ULL, sat + 79315 }, { 0x0001001000801040ULL, sat + 51779 },
{ 0x0000004040008001ULL, sat + 13586 }, { 0x0000006800cdfff4ULL, sat + 19323 },
{ 0x0040200010080010ULL, sat + 70612 }, { 0x0000080010040010ULL, sat + 83652 },
{ 0x0004010008020008ULL, sat + 63110 }, { 0x0000040020200200ULL, sat + 34496 },
{ 0x0002008010100100ULL, sat + 84966 }, { 0x0000008020010020ULL, sat + 54341 },
{ 0x0000008020200040ULL, sat + 60421 }, { 0x0000820020004020ULL, sat + 86402 },
{ 0x00fffd1800300030ULL, sat + 50245 }, { 0x007fff7fbfd40020ULL, sat + 76622 },
{ 0x003fffbd00180018ULL, sat + 84676 }, { 0x001fffde80180018ULL, sat + 78757 },
{ 0x000fffe0bfe80018ULL, sat + 37346 }, { 0x0001000080202001ULL, sat + 370 },
{ 0x0003fffbff980180ULL, sat + 42182 }, { 0x0001fffdff9000e0ULL, sat + 45385 },
{ 0x00fffefeebffd800ULL, sat + 61659 }, { 0x007ffff7ffc01400ULL, sat + 12790 },
{ 0x003fffbfe4ffe800ULL, sat + 16762 }, { 0x001ffff01fc03000ULL, sat + 0 },
{ 0x000fffe7f8bfe800ULL, sat + 38380 }, { 0x0007ffdfdf3ff808ULL, sat + 11098 },
{ 0x0003fff85fffa804ULL, sat + 21803 }, { 0x0001fffd75ffa802ULL, sat + 39189 },
{ 0x00ffffd7ffebffd8ULL, sat + 58628 }, { 0x007fff75ff7fbfd8ULL, sat + 44116 },
{ 0x003fff863fbf7fd8ULL, sat + 78357 }, { 0x001fffbfdfd7ffd8ULL, sat + 44481 },
{ 0x000ffff810280028ULL, sat + 64134 }, { 0x0007ffd7f7feffd8ULL, sat + 41759 },
{ 0x0003fffc0c480048ULL, sat + 1394 }, { 0x0001ffffafd7ffd8ULL, sat + 40910 },
{ 0x00ffffe4ffdfa3baULL, sat + 66516 }, { 0x007fffef7ff3d3daULL, sat + 3897 },
{ 0x003fffbfdfeff7faULL, sat + 3930 }, { 0x001fffeff7fbfc22ULL, sat + 72934 },
{ 0x0000020408001001ULL, sat + 72662 }, { 0x0007fffeffff77fdULL, sat + 56325 },
{ 0x0003ffffbf7dfeecULL, sat + 66501 }, { 0x0001ffff9dffa333ULL, sat + 14826 }
};

Magic<BISHOP> BishopMagics[SQUARE_NB] = {
{ 0x007fbfbfbfbfbfffULL, sat + 5378 }, { 0x0000a060401007fcULL, sat + 4093 },
{ 0x0001004008020000ULL, sat + 4314 }, { 0x0000806004000000ULL, sat + 6587 },
{ 0x0000100400000000ULL, sat + 6491 }, { 0x000021c100b20000ULL, sat + 6330 },
{ 0x0000040041008000ULL, sat + 5609 }, { 0x00000fb0203fff80ULL, sat + 22236 },
{ 0x0000040100401004ULL, sat + 6106 }, { 0x0000020080200802ULL, sat + 5625 },
{ 0x0000004010202000ULL, sat + 16785 }, { 0x0000008060040000ULL, sat + 16817 },
{ 0x0000004402000000ULL, sat + 6842 }, { 0x0000000801008000ULL, sat + 7003 },
{ 0x000007efe0bfff80ULL, sat + 4197 }, { 0x0000000820820020ULL, sat + 7356 },
{ 0x0000400080808080ULL, sat + 4602 }, { 0x00021f0100400808ULL, sat + 4538 },
{ 0x00018000c06f3fffULL, sat + 29531 }, { 0x0000258200801000ULL, sat + 45393 },
{ 0x0000240080840000ULL, sat + 12420 }, { 0x000018000c03fff8ULL, sat + 15763 },
{ 0x00000a5840208020ULL, sat + 5050 }, { 0x0000020008208020ULL, sat + 4346 },
{ 0x0000804000810100ULL, sat + 6074 }, { 0x0001011900802008ULL, sat + 7866 },
{ 0x0000804000810100ULL, sat + 32139 }, { 0x000100403c0403ffULL, sat + 57673 },
{ 0x00078402a8802000ULL, sat + 55365 }, { 0x0000101000804400ULL, sat + 15818 },
{ 0x0000080800104100ULL, sat + 5562 }, { 0x00004004c0082008ULL, sat + 6390 },
{ 0x0001010120008020ULL, sat + 7930 }, { 0x000080809a004010ULL, sat + 13329 },
{ 0x0007fefe08810010ULL, sat + 7170 }, { 0x0003ff0f833fc080ULL, sat + 27267 },
{ 0x007fe08019003042ULL, sat + 53787 }, { 0x003fffefea003000ULL, sat + 5097 },
{ 0x0000101010002080ULL, sat + 6643 }, { 0x0000802005080804ULL, sat + 6138 },
{ 0x0000808080a80040ULL, sat + 7418 }, { 0x0000104100200040ULL, sat + 7898 },
{ 0x0003ffdf7f833fc0ULL, sat + 42012 }, { 0x0000008840450020ULL, sat + 57350 },
{ 0x00007ffc80180030ULL, sat + 22813 }, { 0x007fffdd80140028ULL, sat + 56693 },
{ 0x00020080200a0004ULL, sat + 5818 }, { 0x0000101010100020ULL, sat + 7098 },
{ 0x0007ffdfc1805000ULL, sat + 4451 }, { 0x0003ffefe0c02200ULL, sat + 4709 },
{ 0x0000000820806000ULL, sat + 4794 }, { 0x0000000008403000ULL, sat + 13364 },
{ 0x0000000100202000ULL, sat + 4570 }, { 0x0000004040802000ULL, sat + 4282 },
{ 0x0004010040100400ULL, sat + 14964 }, { 0x00006020601803f4ULL, sat + 4026 },
{ 0x0003ffdfdfc28048ULL, sat + 4826 }, { 0x0000000820820020ULL, sat + 7354 },
{ 0x0000000008208060ULL, sat + 4848 }, { 0x0000000000808020ULL, sat + 15946 },
{ 0x0000000001002020ULL, sat + 14932 }, { 0x0000000401002008ULL, sat + 16588 },
{ 0x0000004040404040ULL, sat + 6905 }, { 0x007fff9fdf7ff813ULL, sat + 16076 }
};

#undef sat

/// safe_destination() returns the bitboard of target square for the given step
/// from the given square. If the step is off the board, returns empty bitboard.

Expand Down Expand Up @@ -166,8 +164,8 @@ void Bitboards::init() {
for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
SquareDistance[s1][s2] = std::max(distance<File>(s1, s2), distance<Rank>(s1, s2));

init_magics< ROOK>(SlideAttackTable, RookMagics);
init_magics<BISHOP>(SlideAttackTable, BishopMagics);
init_magics< ROOK >( RookMagics );
init_magics<BISHOP>(BishopMagics);

for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
{
Expand Down Expand Up @@ -220,7 +218,7 @@ namespace {
// As a reference see www.chessprogramming.org/Magic_Bitboards. In particular,
// here we use the so called "fixed shift fancy magic bitboards" approach.
template<PieceType Pt>
void init_magics(Bitboard table[], Magic<Pt> magics[]) {
void init_magics(Magic<Pt> magics[]) {
int size = 0;

for (Square s = SQ_A1; s <= SQ_H8; ++s)
Expand All @@ -229,7 +227,6 @@ namespace {
Bitboard edges = ((Rank1BB | Rank8BB) & ~rank_bb(s)) | ((FileABB | FileHBB) & ~file_bb(s));

Magic<Pt>& m = magics[s];
KnownMagic knownMagic = Pt == ROOK ? KnownRookMagics[s] : KnownBishopMagics[s];

// Given a square 's', the mask is the bitboard of sliding attacks from
// 's' computed on an empty board.
Expand All @@ -241,18 +238,8 @@ namespace {
// previous square's end offset as the current square's starting offset.
// Rooks are stored in entries 0 through 0x18FFFF,
// bishops are stored in entries 0x190000 through 0x19147F.
constexpr int startOffset = Pt == ROOK ? 0 : 0x19000;
m.attacks = s == SQ_A1 ? table + startOffset : magics[s - 1].attacks + size;
}
else
{
// For magic bitboards indexing we use pre-computed magics values and
// offsets. Since we are using the "fixed shift" approach we do not need
// to calculate the shift, because the magic product will always resolve
// a unique index using a 64-12 bit shift for rooks and 64-9 bit shift
// for bishops.
m.magic = knownMagic.magic;
m.attacks = table + knownMagic.offset;
constexpr unsigned startOffset = Pt == ROOK ? 0 : 0x19000;
m.attacks = s == SQ_A1 ? SlideAttackTable + startOffset : magics[s - 1].attacks + size;
}

// Use Carry-Rippler trick to enumerate all subsets of masks[s] and
Expand All @@ -262,9 +249,9 @@ namespace {
do {
Bitboard reference = sliding_attack(Pt, s, occupied);

unsigned index = m.index(occupied);
assert(m.attacks[index] == 0 || m.attacks[index] == reference);
m.attacks[index] = reference;
unsigned idx = m.index(occupied);
assert(m.attacks[idx] == 0 || m.attacks[idx] == reference);
m.attacks[idx] = reference;

size++;
occupied = (occupied - m.mask) & m.mask;
Expand Down
10 changes: 2 additions & 8 deletions src/bitboard.h
View file
Expand Up @@ -81,21 +81,15 @@ extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];


// Used for storing pre-computed magics and their positions in
// an attack table.
struct KnownMagic
{
Bitboard magic;
unsigned offset;
};

// Magic holds all magic bitboards relevant data for a single square
template<PieceType Pt>
struct Magic {
Bitboard mask;
Bitboard magic;
Bitboard* attacks;

Magic(Bitboard m, Bitboard *table) : magic(m), attacks(table) {};

// Compute the attack's index using either the BMI2 PEXT instruction,
// or by the 'fixed shift fancy magic bitboards' approach.
unsigned index(Bitboard occupied) const {
Expand Down

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