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Diffstat (limited to 'src/sig.c')
| -rwxr-xr-x | src/sig.c | 244 |
1 files changed, 244 insertions, 0 deletions
diff --git a/src/sig.c b/src/sig.c new file mode 100755 index 0000000..7c6c521 --- /dev/null +++ b/src/sig.c @@ -0,0 +1,244 @@ +/** + +Copyright (c) Scott Gasch + +Module Name: + + sig.c + +Abstract: + + Position signature code... the algorithm is a Zobrist hash scheme. + Every piece has a different 64-bit "seed" for every different + square. Plus some non-piece/location features of a position (such + as legal castling rights or the en passant location) have 64-bit + "seed" keys. The position's signature is the xor sum of all these + seeds. A position's pawn hash signature is the xor sum of all + pawn-related seeds. These signatures, once computed, can be + incrementally maintained by just xoring off the seed of a moving + piece's from location and xoring on the seed of its to location. + These signatures are used as the basis for the pawn hash and main + transposition table code. + +Author: + + Scott Gasch ([email protected]) 09 May 2004 + +Revision History: + + $Id: sig.c 345 2007-12-02 22:56:42Z scott $ + +**/ + +#include "chess.h" + +UINT64 g_u64SigSeeds[128][7][2]; +UINT64 g_u64PawnSigSeeds[128][2]; +UINT64 g_u64CastleSigSeeds[16]; +UINT64 g_u64EpSigSeeds[9]; + +void +InitializeSigSystem(void) +/** + +Routine description: + + Populate the arrays of signature keys (see above) used to generate + normal and pawn signatures for POSITIONs. + +Parameters: + + void + +Return value: + + void + +**/ +{ + ULONG x, y, z; + UINT uChecksum = 0; + ULONG uRandom; + + memset(g_u64SigSeeds, 0, sizeof(g_u64SigSeeds)); + memset(g_u64PawnSigSeeds, 0, sizeof(g_u64PawnSigSeeds)); + memset(g_u64CastleSigSeeds, 0, sizeof(g_u64CastleSigSeeds)); + memset(g_u64EpSigSeeds, 0, sizeof(g_u64EpSigSeeds)); + seedMT(2222); + + for (x = A; x <= H+1; x++) + { + // + // Do en-passant sig + // + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64EpSigSeeds[x] = (UINT64)uRandom << 32; + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64EpSigSeeds[x] |= uRandom; + g_u64EpSigSeeds[x] &= ~1; + } + + // + // Foreach square on the board. + // + for (x = 0; x < 128; x++) + { + // + // For both colors + // + FOREACH_COLOR(z) + { + // + // Do the pawn sigs + // + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64PawnSigSeeds[x][z] = (UINT64)uRandom << 32; + + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64PawnSigSeeds[x][z] |= uRandom; + g_u64PawnSigSeeds[x][z] &= ~1; + + // + // Do the piece sigs + // + for (y = 0; y < 7; y++) + { + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64SigSeeds[x][y][z] = (UINT64)uRandom << 32; + + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64SigSeeds[x][y][z] |= uRandom; + g_u64SigSeeds[x][y][z] &= ~1; + } + } + } + + // + // For all castle permissions + // + for (x = 0; x < 16; x++) + { + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64CastleSigSeeds[x] = (UINT64)uRandom << 32; + + uRandom = randomMT(); + uChecksum ^= uRandom; + g_u64CastleSigSeeds[x] |= uRandom; + g_u64CastleSigSeeds[x] &= ~1; + } + + // + // Make sure we got what we expected. + // + if (uChecksum != 0xac19ab2b) + { + UtilPanic(DETECTED_INCORRECT_INITIALIZATION, + NULL, + "signature system", + (void *)uChecksum, + (void *)0xac19ab2b, + __FILE__, __LINE__); + } +} + + +UINT64 +ComputePawnSig(POSITION *pos) +/** + +Routine description: + + Given a board, recompute the pawn signature from scratch. + +Parameters: + + POSITION *pos + +Return value: + + UINT64 + +**/ +{ + register COOR c; + PIECE p; + UINT64 u64Sum = 0; + + FOREACH_SQUARE(c) + { + if (!IS_ON_BOARD(c)) continue; + + p = pos->rgSquare[c].pPiece; + if (IS_PAWN(p)) + { + u64Sum ^= g_u64PawnSigSeeds[c][GET_COLOR(p)]; + } + } + return(u64Sum); +} + + +UINT64 +ComputeSig(POSITION *pos) +/** + +Routine description: + + Given a board, recompute the main signature from scratch. + +Parameters: + + POSITION *pos + +Return value: + + UINT64 + +**/ +{ + register COOR c; + UINT64 u64Sum = 0; + PIECE p; + + FOREACH_SQUARE(c) + { + if (!IS_ON_BOARD(c)) continue; + + p = pos->rgSquare[c].pPiece; + + if (!IS_EMPTY(p) && !IS_PAWN(p)) + { + ASSERT(IS_VALID_PIECE(p)); + u64Sum ^= g_u64SigSeeds[c][PIECE_TYPE(p)][GET_COLOR(p)]; + } + } + + // + // Update the signature to reflect the castle permissions and ep + // square at this point. + // + u64Sum ^= g_u64CastleSigSeeds[pos->bvCastleInfo]; + u64Sum ^= g_u64EpSigSeeds[FILE(pos->cEpSquare)]; + + // + // Update the low order bit to reflect the side to move. + // + if (pos->uToMove == WHITE) + { + u64Sum |= 1; + } + else + { + u64Sum &= ~1; + } + ASSERT((u64Sum & 1) == pos->uToMove); + + return(u64Sum); +} |