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https://github.com/sockspls/badfish
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Reformat kpk bitbase
Simplify and streamline the code. Verified all the resulting bitbases are not changed. No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
parent
1a1742ac4f
commit
a94fd3bbec
1 changed files with 112 additions and 160 deletions
272
src/bitbase.cpp
272
src/bitbase.cpp
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@ -25,43 +25,47 @@
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namespace {
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enum Result {
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RESULT_UNKNOWN,
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RESULT_INVALID,
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RESULT_WIN,
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RESULT_DRAW
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INVALID = 0,
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UNKNOWN = 1,
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DRAW = 2,
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WIN = 4
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};
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inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
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struct KPKPosition {
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Result classify_knowns(int index);
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Result classify(int index, Result db[]);
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Result classify_leaf(int idx);
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Result classify(int idx, Result db[]);
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private:
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void from_index(int index);
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Result classify_white(const Result db[]);
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Result classify_black(const Result db[]);
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Bitboard wk_attacks() const { return StepAttacksBB[W_KING][whiteKingSquare]; }
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Bitboard bk_attacks() const { return StepAttacksBB[B_KING][blackKingSquare]; }
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Bitboard pawn_attacks() const { return StepAttacksBB[W_PAWN][pawnSquare]; }
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template<Color Us> Result classify(const Result db[]) const;
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Square whiteKingSquare, blackKingSquare, pawnSquare;
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Color sideToMove;
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template<Color Us> Bitboard k_attacks() const {
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return Us == WHITE ? StepAttacksBB[W_KING][wksq] : StepAttacksBB[B_KING][bksq];
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}
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Bitboard p_attacks() const { return StepAttacksBB[W_PAWN][psq]; }
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void decode_index(int idx);
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Square wksq, bksq, psq;
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Color stm;
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};
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// The possible pawns squares are 24, the first 4 files and ranks from 2 to 7
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const int IndexMax = 2 * 24 * 64 * 64; // color * wp_sq * wk_sq * bk_sq = 196608
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const int IndexMax = 2 * 24 * 64 * 64; // stm * wp_sq * wk_sq * bk_sq = 196608
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// Each uint32_t stores results of 32 positions, one per bit
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uint32_t KPKBitbase[IndexMax / 32];
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int compute_index(Square wksq, Square bksq, Square wpsq, Color stm);
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int index(Square wksq, Square bksq, Square psq, Color stm);
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}
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uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) {
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int index = compute_index(wksq, bksq, wpsq, stm);
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return KPKBitbase[index / 32] & (1 << (index & 31));
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int idx = index(wksq, bksq, wpsq, stm);
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return KPKBitbase[idx / 32] & (1 << (idx & 31));
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}
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@ -69,24 +73,23 @@ void kpk_bitbase_init() {
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Result db[IndexMax];
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KPKPosition pos;
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int index, bit, repeat = 1;
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int idx, bit, repeat = 1;
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// Initialize table
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for (index = 0; index < IndexMax; index++)
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db[index] = pos.classify_knowns(index);
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// Initialize table with known win / draw positions
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for (idx = 0; idx < IndexMax; idx++)
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db[idx] = pos.classify_leaf(idx);
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// Iterate until all positions are classified (30 cycles needed)
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while (repeat)
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for (repeat = index = 0; index < IndexMax; index++)
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if ( db[index] == RESULT_UNKNOWN
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&& pos.classify(index, db) != RESULT_UNKNOWN)
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for (repeat = idx = 0; idx < IndexMax; idx++)
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if (db[idx] == UNKNOWN && (db[idx] = pos.classify(idx, db)) != UNKNOWN)
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repeat = 1;
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// Map 32 position results into one KPKBitbase[] entry
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for (index = 0; index < IndexMax / 32; index++)
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for (idx = 0; idx < IndexMax / 32; idx++)
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for (bit = 0; bit < 32; bit++)
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if (db[32 * index + bit] == RESULT_WIN)
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KPKBitbase[index] |= (1 << bit);
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if (db[32 * idx + bit] == WIN)
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KPKBitbase[idx] |= 1 << bit;
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}
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@ -102,170 +105,119 @@ namespace {
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// bit 13-14: white pawn file (from FILE_A to FILE_D)
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// bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1)
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int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) {
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int index(Square w, Square b, Square p, Color c) {
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assert(file_of(wpsq) <= FILE_D);
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assert(file_of(p) <= FILE_D);
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int p = file_of(wpsq) + 4 * (rank_of(wpsq) - 1);
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int r = stm + 2 * bksq + 128 * wksq + 8192 * p;
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assert(r >= 0 && r < IndexMax);
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return r;
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return c + (b << 1) + (w << 7) + (file_of(p) << 13) + ((rank_of(p) - 1) << 15);
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}
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void KPKPosition::from_index(int index) {
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void KPKPosition::decode_index(int idx) {
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int s = index >> 13;
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sideToMove = Color(index & 1);
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blackKingSquare = Square((index >> 1) & 63);
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whiteKingSquare = Square((index >> 7) & 63);
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pawnSquare = make_square(File(s & 3), Rank((s >> 2) + 1));
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stm = Color(idx & 1);
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bksq = Square((idx >> 1) & 63);
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wksq = Square((idx >> 7) & 63);
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psq = make_square(File((idx >> 13) & 3), Rank((idx >> 15) + 1));
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}
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Result KPKPosition::classify_knowns(int index) {
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Result KPKPosition::classify_leaf(int idx) {
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from_index(index);
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decode_index(idx);
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// Check if two pieces are on the same square
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if ( whiteKingSquare == pawnSquare
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|| whiteKingSquare == blackKingSquare
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|| blackKingSquare == pawnSquare)
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return RESULT_INVALID;
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// Check if two pieces are on the same square or if a king can be captured
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if ( wksq == psq || wksq == bksq || bksq == psq
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|| (k_attacks<WHITE>() & bksq)
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|| (stm == WHITE && (p_attacks() & bksq)))
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return INVALID;
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// Check if a king can be captured
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if ( (wk_attacks() & blackKingSquare)
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|| ((pawn_attacks() & blackKingSquare) && sideToMove == WHITE))
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return RESULT_INVALID;
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// The position is an immediate win if it is white to move and the
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// white pawn can be promoted without getting captured.
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if ( rank_of(pawnSquare) == RANK_7
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&& sideToMove == WHITE
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&& whiteKingSquare != pawnSquare + DELTA_N
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&& ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1
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|| (wk_attacks() & (pawnSquare + DELTA_N))))
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return RESULT_WIN;
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// The position is an immediate win if it is white to move and the white
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// pawn can be promoted without getting captured.
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if ( rank_of(psq) == RANK_7
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&& stm == WHITE
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&& wksq != psq + DELTA_N
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&& ( square_distance(bksq, psq + DELTA_N) > 1
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||(k_attacks<WHITE>() & (psq + DELTA_N))))
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return WIN;
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// Check for known draw positions
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//
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// Case 1: Stalemate
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if ( sideToMove == BLACK
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&& !(bk_attacks() & ~(wk_attacks() | pawn_attacks())))
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return RESULT_DRAW;
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if ( stm == BLACK
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&& !(k_attacks<BLACK>() & ~(k_attacks<WHITE>() | p_attacks())))
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return DRAW;
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// Case 2: King can capture pawn
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if ( sideToMove == BLACK
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&& (bk_attacks() & pawnSquare) && !(wk_attacks() & pawnSquare))
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return RESULT_DRAW;
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// Case 2: King can capture undefended pawn
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if ( stm == BLACK
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&& (k_attacks<BLACK>() & psq & ~k_attacks<WHITE>()))
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return DRAW;
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// Case 3: Black king in front of white pawn
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if ( blackKingSquare == pawnSquare + DELTA_N
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&& rank_of(pawnSquare) < RANK_7)
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return RESULT_DRAW;
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if ( bksq == psq + DELTA_N
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&& rank_of(psq) < RANK_7)
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return DRAW;
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// Case 4: White king in front of pawn and black has opposition
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if ( whiteKingSquare == pawnSquare + DELTA_N
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&& blackKingSquare == pawnSquare + DELTA_N + DELTA_N + DELTA_N
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&& rank_of(pawnSquare) < RANK_5
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&& sideToMove == WHITE)
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return RESULT_DRAW;
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if ( stm == WHITE
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&& wksq == psq + DELTA_N
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&& bksq == wksq + DELTA_N + DELTA_N
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&& rank_of(psq) < RANK_5)
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return DRAW;
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// Case 5: Stalemate with rook pawn
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if ( blackKingSquare == SQ_A8
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&& file_of(pawnSquare) == FILE_A)
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return RESULT_DRAW;
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if ( bksq == SQ_A8
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&& file_of(psq) == FILE_A)
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return DRAW;
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return RESULT_UNKNOWN;
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return UNKNOWN;
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}
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Result KPKPosition::classify(int index, Result db[]) {
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template<Color Us>
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Result KPKPosition::classify(const Result db[]) const {
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from_index(index);
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db[index] = (sideToMove == WHITE ? classify_white(db) : classify_black(db));
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return db[index];
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}
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Result KPKPosition::classify_white(const Result db[]) {
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// If one move leads to a position classified as RESULT_WIN, the result
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// of the current position is RESULT_WIN. If all moves lead to positions
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// classified as RESULT_DRAW, the current position is classified RESULT_DRAW
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// otherwise the current position is classified as RESULT_UNKNOWN.
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bool unknownFound = false;
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Bitboard b;
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Square s;
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Result r;
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// King moves
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b = wk_attacks();
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while (b)
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{
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s = pop_1st_bit(&b);
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r = db[compute_index(s, blackKingSquare, pawnSquare, BLACK)];
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if (r == RESULT_WIN)
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return RESULT_WIN;
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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}
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// Pawn moves
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if (rank_of(pawnSquare) < RANK_7)
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{
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s = pawnSquare + DELTA_N;
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r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)];
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if (r == RESULT_WIN)
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return RESULT_WIN;
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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// Double pawn push
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if (rank_of(s) == RANK_3 && r != RESULT_INVALID)
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{
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s += DELTA_N;
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r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)];
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if (r == RESULT_WIN)
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return RESULT_WIN;
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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}
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}
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return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
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}
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Result KPKPosition::classify_black(const Result db[]) {
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// If one move leads to a position classified as RESULT_DRAW, the result
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// of the current position is RESULT_DRAW. If all moves lead to positions
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// classified as RESULT_WIN, the position is classified as RESULT_WIN.
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// White to Move: If one move leads to a position classified as RESULT_WIN,
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// the result of the current position is RESULT_WIN. If all moves lead to
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// positions classified as RESULT_DRAW, the current position is classified
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// RESULT_DRAW otherwise the current position is classified as RESULT_UNKNOWN.
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//
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// Black to Move: If one move leads to a position classified as RESULT_DRAW,
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// the result of the current position is RESULT_DRAW. If all moves lead to
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// positions classified as RESULT_WIN, the position is classified RESULT_WIN.
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// Otherwise, the current position is classified as RESULT_UNKNOWN.
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bool unknownFound = false;
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Bitboard b;
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Square s;
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Result r;
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Result r = INVALID;
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Bitboard b = k_attacks<Us>();
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// King moves
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b = bk_attacks();
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while (b)
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{
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s = pop_1st_bit(&b);
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r = db[compute_index(whiteKingSquare, s, pawnSquare, WHITE)];
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r |= Us == WHITE ? db[index(pop_1st_bit(&b), bksq, psq, BLACK)]
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: db[index(wksq, pop_1st_bit(&b), psq, WHITE)];
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if (r == RESULT_DRAW)
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return RESULT_DRAW;
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if (Us == WHITE && (r & WIN))
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return WIN;
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if (r == RESULT_UNKNOWN)
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unknownFound = true;
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if (Us == BLACK && (r & DRAW))
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return DRAW;
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}
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return unknownFound ? RESULT_UNKNOWN : RESULT_WIN;
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if (Us == WHITE && rank_of(psq) < RANK_7)
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{
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Square s = psq + DELTA_N;
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r |= db[index(wksq, bksq, s, BLACK)]; // Single push
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if (rank_of(s) == RANK_3 && s != wksq && s != bksq)
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r |= db[index(wksq, bksq, s + DELTA_N, BLACK)]; // Double push
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if (r & WIN)
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return WIN;
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}
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return r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN;
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}
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Result KPKPosition::classify(int idx, Result db[]) {
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decode_index(idx);
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return stm == WHITE ? classify<WHITE>(db) : classify<BLACK>(db);
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}
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}
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