X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitboard.cpp;h=c67c01a62ff258dfaa0438152cb1d2e45304d8e6;hp=b1bf4d91e583b3f07f1ac53cb669dce2a4522eb0;hb=099b5e45e6fb84c0c6ac9c867e0902e0195d97a5;hpb=3092f0c6460c831e666d54389710394c52a86ed9
diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index b1bf4d91..c67c01a6 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
@@ -17,184 +17,54 @@
along with this program. If not, see .
*/
+#include
+#include
#include
#include "bitboard.h"
#include "bitcount.h"
+#include "rkiss.h"
-// Global bitboards definitions with static storage duration are
-// automatically set to zero before enter main().
-Bitboard RAttacks[0x19000];
-Bitboard BAttacks[0x1480];
+CACHE_LINE_ALIGNMENT
-Magics RMagics[64];
-Magics BMagics[64];
+Bitboard RMasks[64];
+Bitboard RMagics[64];
+Bitboard* RAttacks[64];
+unsigned RShifts[64];
-Bitboard SetMaskBB[65];
-Bitboard ClearMaskBB[65];
+Bitboard BMasks[64];
+Bitboard BMagics[64];
+Bitboard* BAttacks[64];
+unsigned BShifts[64];
-Bitboard SquaresByColorBB[2];
+Bitboard SquareBB[64];
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];
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 {
-#if defined(IS_64BIT)
-
-const uint64_t DeBruijnMagic = 0x218A392CD3D5DBFULL;
-
-const uint64_t BMult[64] = {
- 0x0440049104032280ULL, 0x1021023C82008040ULL, 0x0404040082000048ULL,
- 0x48C4440084048090ULL, 0x2801104026490000ULL, 0x4100880442040800ULL,
- 0x0181011002E06040ULL, 0x9101004104200E00ULL, 0x1240848848310401ULL,
- 0x2000142828050024ULL, 0x00001004024D5000ULL, 0x0102044400800200ULL,
- 0x8108108820112000ULL, 0xA880818210C00046ULL, 0x4008008801082000ULL,
- 0x0060882404049400ULL, 0x0104402004240810ULL, 0x000A002084250200ULL,
- 0x00100B0880801100ULL, 0x0004080201220101ULL, 0x0044008080A00000ULL,
- 0x0000202200842000ULL, 0x5006004882D00808ULL, 0x0000200045080802ULL,
- 0x0086100020200601ULL, 0xA802080A20112C02ULL, 0x0080411218080900ULL,
- 0x000200A0880080A0ULL, 0x9A01010000104000ULL, 0x0028008003100080ULL,
- 0x0211021004480417ULL, 0x0401004188220806ULL, 0x00825051400C2006ULL,
- 0x00140C0210943000ULL, 0x0000242800300080ULL, 0x00C2208120080200ULL,
- 0x2430008200002200ULL, 0x1010100112008040ULL, 0x8141050100020842ULL,
- 0x0000822081014405ULL, 0x800C049E40400804ULL, 0x4A0404028A000820ULL,
- 0x0022060201041200ULL, 0x0360904200840801ULL, 0x0881A08208800400ULL,
- 0x0060202C00400420ULL, 0x1204440086061400ULL, 0x0008184042804040ULL,
- 0x0064040315300400ULL, 0x0C01008801090A00ULL, 0x0808010401140C00ULL,
- 0x04004830C2020040ULL, 0x0080005002020054ULL, 0x40000C14481A0490ULL,
- 0x0010500101042048ULL, 0x1010100200424000ULL, 0x0000640901901040ULL,
- 0x00000A0201014840ULL, 0x00840082AA011002ULL, 0x010010840084240AULL,
- 0x0420400810420608ULL, 0x8D40230408102100ULL, 0x4A00200612222409ULL,
- 0x0A08520292120600ULL
-};
-
-const uint64_t RMult[64] = {
- 0x0A8002C000108020ULL, 0x4440200140003000ULL, 0x8080200010011880ULL,
- 0x0380180080141000ULL, 0x1A00060008211044ULL, 0x410001000A0C0008ULL,
- 0x9500060004008100ULL, 0x0100024284A20700ULL, 0x0000802140008000ULL,
- 0x0080C01002A00840ULL, 0x0402004282011020ULL, 0x9862000820420050ULL,
- 0x0001001448011100ULL, 0x6432800200800400ULL, 0x040100010002000CULL,
- 0x0002800D0010C080ULL, 0x90C0008000803042ULL, 0x4010004000200041ULL,
- 0x0003010010200040ULL, 0x0A40828028001000ULL, 0x0123010008000430ULL,
- 0x0024008004020080ULL, 0x0060040001104802ULL, 0x00582200028400D1ULL,
- 0x4000802080044000ULL, 0x0408208200420308ULL, 0x0610038080102000ULL,
- 0x3601000900100020ULL, 0x0000080080040180ULL, 0x00C2020080040080ULL,
- 0x0080084400100102ULL, 0x4022408200014401ULL, 0x0040052040800082ULL,
- 0x0B08200280804000ULL, 0x008A80A008801000ULL, 0x4000480080801000ULL,
- 0x0911808800801401ULL, 0x822A003002001894ULL, 0x401068091400108AULL,
- 0x000004A10A00004CULL, 0x2000800640008024ULL, 0x1486408102020020ULL,
- 0x000100A000D50041ULL, 0x00810050020B0020ULL, 0x0204000800808004ULL,
- 0x00020048100A000CULL, 0x0112000831020004ULL, 0x0009000040810002ULL,
- 0x0440490200208200ULL, 0x8910401000200040ULL, 0x6404200050008480ULL,
- 0x4B824A2010010100ULL, 0x04080801810C0080ULL, 0x00000400802A0080ULL,
- 0x8224080110026400ULL, 0x40002C4104088200ULL, 0x01002100104A0282ULL,
- 0x1208400811048021ULL, 0x3201014A40D02001ULL, 0x0005100019200501ULL,
- 0x0101000208001005ULL, 0x0002008450080702ULL, 0x001002080301D00CULL,
- 0x410201CE5C030092ULL
-};
-
-const int BShift[64] = {
- 58, 59, 59, 59, 59, 59, 59, 58, 59, 59, 59, 59, 59, 59, 59, 59,
- 59, 59, 57, 57, 57, 57, 59, 59, 59, 59, 57, 55, 55, 57, 59, 59,
- 59, 59, 57, 55, 55, 57, 59, 59, 59, 59, 57, 57, 57, 57, 59, 59,
- 59, 59, 59, 59, 59, 59, 59, 59, 58, 59, 59, 59, 59, 59, 59, 58
-};
-
-const int RShift[64] = {
- 52, 53, 53, 53, 53, 53, 53, 52, 53, 54, 54, 54, 54, 54, 54, 53,
- 53, 54, 54, 54, 54, 54, 54, 53, 53, 54, 54, 54, 54, 54, 54, 53,
- 53, 54, 54, 54, 54, 54, 54, 53, 53, 54, 54, 54, 54, 54, 54, 53,
- 53, 54, 54, 54, 54, 54, 54, 53, 52, 53, 53, 53, 53, 53, 53, 52
-};
-
-#else // if !defined(IS_64BIT)
-
-const uint32_t DeBruijnMagic = 0x783A9B23;
-
-const uint64_t BMult[64] = {
- 0x54142844C6A22981ULL, 0x710358A6EA25C19EULL, 0x704F746D63A4A8DCULL,
- 0xBFED1A0B80F838C5ULL, 0x90561D5631E62110ULL, 0x2804260376E60944ULL,
- 0x84A656409AA76871ULL, 0xF0267F64C28B6197ULL, 0x70764EBB762F0585ULL,
- 0x92AA09E0CFE161DEULL, 0x41EE1F6BB266F60EULL, 0xDDCBF04F6039C444ULL,
- 0x5A3FAB7BAC0D988AULL, 0xD3727877FA4EAA03ULL, 0xD988402D868DDAAEULL,
- 0x812B291AFA075C7CULL, 0x94FAF987B685A932ULL, 0x3ED867D8470D08DBULL,
- 0x92517660B8901DE8ULL, 0x2D97E43E058814B4ULL, 0x880A10C220B25582ULL,
- 0xC7C6520D1F1A0477ULL, 0xDBFC7FBCD7656AA6ULL, 0x78B1B9BFB1A2B84FULL,
- 0x2F20037F112A0BC1ULL, 0x657171EA2269A916ULL, 0xC08302B07142210EULL,
- 0x0880A4403064080BULL, 0x3602420842208C00ULL, 0x852800DC7E0B6602ULL,
- 0x595A3FBBAA0F03B2ULL, 0x9F01411558159D5EULL, 0x2B4A4A5F88B394F2ULL,
- 0x4AFCBFFC292DD03AULL, 0x4A4094A3B3F10522ULL, 0xB06F00B491F30048ULL,
- 0xD5B3820280D77004ULL, 0x8B2E01E7C8E57A75ULL, 0x2D342794E886C2E6ULL,
- 0xC302C410CDE21461ULL, 0x111F426F1379C274ULL, 0xE0569220ABB31588ULL,
- 0x5026D3064D453324ULL, 0xE2076040C343CD8AULL, 0x93EFD1E1738021EEULL,
- 0xB680804BED143132ULL, 0x44E361B21986944CULL, 0x44C60170EF5C598CULL,
- 0xF4DA475C195C9C94ULL, 0xA3AFBB5F72060B1DULL, 0xBC75F410E41C4FFCULL,
- 0xB51C099390520922ULL, 0x902C011F8F8EC368ULL, 0x950B56B3D6F5490AULL,
- 0x3909E0635BF202D0ULL, 0x5744F90206EC10CCULL, 0xDC59FD76317ABBC1ULL,
- 0x881C7C67FCBFC4F6ULL, 0x47CA41E7E440D423ULL, 0xEB0C88112048D004ULL,
- 0x51C60E04359AEF1AULL, 0x1AA1FE0E957A5554ULL, 0xDD9448DB4F5E3104ULL,
- 0xDC01F6DCA4BEBBDCULL,
-};
-
-const uint64_t RMult[64] = {
- 0xD7445CDEC88002C0ULL, 0xD0A505C1F2001722ULL, 0xE065D1C896002182ULL,
- 0x9A8C41E75A000892ULL, 0x8900B10C89002AA8ULL, 0x9B28D1C1D60005A2ULL,
- 0x015D6C88DE002D9AULL, 0xB1DBFC802E8016A9ULL, 0x149A1042D9D60029ULL,
- 0xB9C08050599E002FULL, 0x132208C3AF300403ULL, 0xC1000CE2E9C50070ULL,
- 0x9D9AA13C99020012ULL, 0xB6B078DAF71E0046ULL, 0x9D880182FB6E002EULL,
- 0x52889F467E850037ULL, 0xDA6DC008D19A8480ULL, 0x468286034F902420ULL,
- 0x7140AC09DC54C020ULL, 0xD76FFFFA39548808ULL, 0xEA901C4141500808ULL,
- 0xC91004093F953A02ULL, 0x02882AFA8F6BB402ULL, 0xAEBE335692442C01ULL,
- 0x0E904A22079FB91EULL, 0x13A514851055F606ULL, 0x76C782018C8FE632ULL,
- 0x1DC012A9D116DA06ULL, 0x3C9E0037264FFFA6ULL, 0x2036002853C6E4A2ULL,
- 0xE3FE08500AFB47D4ULL, 0xF38AF25C86B025C2ULL, 0xC0800E2182CF9A40ULL,
- 0x72002480D1F60673ULL, 0x2500200BAE6E9B53ULL, 0xC60018C1EEFCA252ULL,
- 0x0600590473E3608AULL, 0x46002C4AB3FE51B2ULL, 0xA200011486BCC8D2ULL,
- 0xB680078095784C63ULL, 0x2742002639BF11AEULL, 0xC7D60021A5BDB142ULL,
- 0xC8C04016BB83D820ULL, 0xBD520028123B4842ULL, 0x9D1600344AC2A832ULL,
- 0x6A808005631C8A05ULL, 0x604600A148D5389AULL, 0xE2E40103D40DEA65ULL,
- 0x945B5A0087C62A81ULL, 0x012DC200CD82D28EULL, 0x2431C600B5F9EF76ULL,
- 0xFB142A006A9B314AULL, 0x06870E00A1C97D62ULL, 0x2A9DB2004A2689A2ULL,
- 0xD3594600CAF5D1A2ULL, 0xEE0E4900439344A7ULL, 0x89C4D266CA25007AULL,
- 0x3E0013A2743F97E3ULL, 0x0180E31A0431378AULL, 0x3A9E465A4D42A512ULL,
- 0x98D0A11A0C0D9CC2ULL, 0x8E711C1ABA19B01EULL, 0x8DCDC836DD201142ULL,
- 0x5AC08A4735370479ULL,
-};
-
-const int BShift[64] = {
- 26, 27, 27, 27, 27, 27, 27, 26, 27, 27, 27, 27, 27, 27, 27, 27,
- 27, 27, 25, 25, 25, 25, 27, 27, 27, 27, 25, 23, 23, 25, 27, 27,
- 27, 27, 25, 23, 23, 25, 27, 27, 27, 27, 25, 25, 25, 25, 27, 27,
- 27, 27, 27, 27, 27, 27, 27, 27, 26, 27, 27, 27, 27, 27, 27, 26
-};
+ CACHE_LINE_ALIGNMENT
-const int RShift[64] = {
- 20, 21, 21, 21, 21, 21, 21, 20, 21, 22, 22, 22, 22, 22, 22, 21,
- 21, 22, 22, 22, 22, 22, 22, 21, 21, 22, 22, 22, 22, 22, 22, 21,
- 21, 22, 22, 22, 22, 22, 22, 21, 21, 22, 22, 22, 22, 22, 22, 21,
- 21, 22, 22, 22, 22, 22, 22, 21, 20, 21, 21, 21, 21, 21, 21, 20
-};
-
-#endif // defined(IS_64BIT)
+ int BSFTable[64];
+ Bitboard RTable[0x19000]; // Storage space for rook attacks
+ Bitboard BTable[0x1480]; // Storage space for bishop attacks
- CACHE_LINE_ALIGNMENT int BSFTable[64];
+ typedef unsigned (Fn)(Square, Bitboard);
- void init_sliding_attacks(Bitboard attacks[], Magics m[], const int shift[],
- const Bitboard mult[], Square deltas[]);
+ void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], unsigned shifts[], Square deltas[], Fn get_index);
}
@@ -207,7 +77,7 @@ void print_bitboard(Bitboard b) {
{
std::cout << "+---+---+---+---+---+---+---+---+" << '\n';
for (File f = FILE_A; f <= FILE_H; f++)
- std::cout << "| " << (bit_is_set(b, make_square(f, r)) ? 'X' : ' ') << ' ';
+ std::cout << "| " << ((b & make_square(f, r)) ? "X " : " ");
std::cout << "|\n";
}
@@ -222,13 +92,13 @@ void print_bitboard(Bitboard b) {
#if defined(IS_64BIT) && !defined(USE_BSFQ)
Square first_1(Bitboard b) {
- return Square(BSFTable[((b & -b) * DeBruijnMagic) >> 58]);
+ return Square(BSFTable[((b & -b) * 0x218A392CD3D5DBFULL) >> 58]);
}
Square pop_1st_bit(Bitboard* b) {
Bitboard bb = *b;
*b &= (*b - 1);
- return Square(BSFTable[((bb & -bb) * DeBruijnMagic) >> 58]);
+ return Square(BSFTable[((bb & -bb) * 0x218A392CD3D5DBFULL) >> 58]);
}
#elif !defined(USE_BSFQ)
@@ -236,7 +106,7 @@ Square pop_1st_bit(Bitboard* b) {
Square first_1(Bitboard b) {
b ^= (b - 1);
uint32_t fold = unsigned(b) ^ unsigned(b >> 32);
- return Square(BSFTable[(fold * DeBruijnMagic) >> 26]);
+ return Square(BSFTable[(fold * 0x783A9B23) >> 26]);
}
// Use type-punning
@@ -263,12 +133,12 @@ Square pop_1st_bit(Bitboard* bb) {
if (u.dw.l)
{
- ret = Square(BSFTable[((u.dw.l ^ (u.dw.l - 1)) * DeBruijnMagic) >> 26]);
+ ret = Square(BSFTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783A9B23) >> 26]);
u.dw.l &= (u.dw.l - 1);
*bb = u.b;
return ret;
}
- ret = Square(BSFTable[((~(u.dw.h ^ (u.dw.h - 1))) * DeBruijnMagic) >> 26]);
+ ret = Square(BSFTable[((~(u.dw.h ^ (u.dw.h - 1))) * 0x783A9B23) >> 26]);
u.dw.h &= (u.dw.h - 1);
*bb = u.b;
return ret;
@@ -277,21 +147,16 @@ 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++)
- {
- SetMaskBB[s] = (1ULL << s);
- ClearMaskBB[s] = ~SetMaskBB[s];
- }
-
- ClearMaskBB[SQ_NONE] = ~EmptyBoardBB;
+ SquareBB[s] = 1ULL << s;
FileBB[FILE_A] = FileABB;
RankBB[RANK_1] = Rank1BB;
@@ -304,8 +169,8 @@ 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++)
@@ -318,130 +183,173 @@ 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 = 1; i < 64; i++)
- if (!CpuIs64Bit) // Matt Taylor's folding trick for 32 bit systems
+ for (int i = 0; i < 64; i++)
+ 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 * DeBruijnMagic) >> 26] = i;
+ BSFTable[(uint32_t)(b * 0x783A9B23) >> 26] = i;
}
else
- BSFTable[((1ULL << i) * DeBruijnMagic) >> 58] = i;
+ BSFTable[((1ULL << i) * 0x218A392CD3D5DBFULL) >> 58] = i;
- int steps[][9] = {
- {0}, {7,9,0}, {17,15,10,6,-6,-10,-15,-17,0}, {0}, {0}, {0}, {9,7,-7,-9,8,1,-1,-8,0}
- };
+ 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 (Square s = SQ_A1; s <= SQ_H8; s++)
- for (PieceType pt = PAWN; pt <= KING; pt++)
+ 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 (square_is_ok(to) && square_distance(s, to) < 3)
- set_bit(&StepAttacksBB[make_piece(c, pt)][s], to);
+ 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_sliding_attacks(RAttacks, RMagics, RShift, RMult, RDeltas);
- init_sliding_attacks(BAttacks, BMagics, BShift, BMult, BDeltas);
+ 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 (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)
+ BetweenBB[s1][s2] |= s;
}
}
namespace {
- Bitboard submask(Bitboard mask, int key) {
+ Bitboard sliding_attack(Square deltas[], Square sq, Bitboard occupied) {
- Bitboard subMask = 0;
- int bitNum = -1;
+ Bitboard attack = 0;
- // Extract an unique submask out of a mask according to the given key
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- if (bit_is_set(mask, s) && bit_is_set(key, Square(++bitNum)))
- set_bit(&subMask, s);
+ for (int i = 0; i < 4; i++)
+ for (Square s = sq + deltas[i];
+ square_is_ok(s) && square_distance(s, s - deltas[i]) == 1;
+ s += deltas[i])
+ {
+ attack |= s;
- return subMask;
- }
+ if (occupied & s)
+ break;
+ }
- Bitboard sliding_attacks(Square sq, Bitboard occupied, Square deltas[], bool skipLast) {
+ return attack;
+ }
- Bitboard attacks = 0;
- for (int i = 0; i < 4; i++)
- {
- Square s = sq + deltas[i];
+ Bitboard pick_random(Bitboard mask, RKISS& rk, int booster) {
- while ( square_is_ok(s)
- && square_distance(s, s - deltas[i]) == 1
- && (!skipLast || !file_distance(s, sq) || (square_file(s) != FILE_A && square_file(s) != FILE_H))
- && (!skipLast || !rank_distance(s, sq) || (square_rank(s) != RANK_1 && square_rank(s) != RANK_8)))
- {
- attacks |= 1ULL << s;
+ Bitboard magic;
- if (occupied & (1ULL << s))
- break;
+ // 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;
- s += deltas[i];
- }
+ while (true)
+ {
+ magic = rk.rand();
+ magic = (magic >> s1) | (magic << (64 - s1));
+ magic &= rk.rand();
+ magic = (magic >> s2) | (magic << (64 - s2));
+ magic &= rk.rand();
+
+ if (BitCount8Bit[(mask * magic) >> 56] >= 6)
+ return magic;
}
- return attacks;
}
- void init_sliding_attacks(Bitboard attacks[], Magics m[], const int shift[],
- const Bitboard mult[], Square deltas[]) {
- Bitboard occupancy, index;
- int maxKey, offset = 0;
- for (Square s = SQ_A1; s <= SQ_H8; s++)
- {
- m[s].offset = offset;
- m[s].mult = mult[s];
- m[s].shift = shift[s];
- m[s].mask = sliding_attacks(s, EmptyBoardBB, deltas, true);
+ // 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.
- maxKey = 1 << (CpuIs64Bit ? 64 - shift[s] : 32 - shift[s]);
+ void init_magics(Bitboard table[], Bitboard* attacks[], Bitboard magics[],
+ Bitboard masks[], unsigned shifts[], Square deltas[], Fn get_index) {
- for (int key = 0; key < maxKey; key++)
- {
- occupancy = submask(m[s].mask, key);
+ 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;
- index = CpuIs64Bit ? occupancy * mult[s]
- : unsigned(occupancy * mult[s] ^ (occupancy >> 32) * (mult[s] >> 32));
+ // attacks[s] is a pointer to the beginning of the attacks table for square 's'
+ attacks[SQ_A1] = table;
- attacks[offset + (index >> shift[s])] = sliding_attacks(s, occupancy, deltas, false);
- }
- offset += maxKey;
+ 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(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 {
+ 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++)
+ {
+ Bitboard& attack = attacks[s][get_index(s, occupancy[i])];
+
+ if (attack && attack != reference[i])
+ break;
+
+ attack = reference[i];
+ }
+ } while (i != size);
}
}
}