From f2950ae2064fed7767b738ba569e33ae7eaad0a7 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Mon, 11 Feb 2013 22:59:37 +0100 Subject: [PATCH] Simplify bitbase.cpp Use a std::vector to store positions and rearrange KPKPosition. No functional change. Signed-off-by: Marco Costalba --- src/bitbase.cpp | 193 ++++++++++++++++++++++-------------------------- src/bitboard.h | 2 +- 2 files changed, 90 insertions(+), 105 deletions(-) diff --git a/src/bitbase.cpp b/src/bitbase.cpp index 5f0438a3..e7ff319d 100644 --- a/src/bitbase.cpp +++ b/src/bitbase.cpp @@ -18,12 +18,32 @@ */ #include +#include #include "bitboard.h" #include "types.h" namespace { + // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 + const unsigned IndexMax = 24*64*64*2; // wp_sq * wk_sq * bk_sq * stm = 196608 + + // Each uint32_t stores results of 32 positions, one per bit + uint32_t KPKBitbase[IndexMax / 32]; + + // A KPK bitbase index is an integer in [0, IndexMax] range + // + // Information is mapped in this way + // + // bit 0: side to move (WHITE or BLACK) + // bit 1- 6: black king square (from SQ_A1 to SQ_H8) + // bit 7-12: white king square (from SQ_A1 to SQ_H8) + // bit 13-14: white pawn file (from FILE_A to FILE_D) + // bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1) + unsigned index(Color stm, Square bksq, Square wksq, Square psq) { + return stm + (bksq << 1) + (wksq << 7) + (file_of(psq) << 13) + ((rank_of(psq) - 1) << 15); + } + enum Result { INVALID = 0, UNKNOWN = 1, @@ -35,153 +55,124 @@ namespace { struct KPKPosition { - Result classify_leaf(int idx); - Result classify(int idx, Result db[]); + void classify_leaf(unsigned idx); - private: - template Result classify(const Result db[]) const; + Result classify(const std::vector& db) + { return stm == WHITE ? classify(db) : classify(db); } - template Bitboard k_attacks() const { - return Us == WHITE ? StepAttacksBB[W_KING][wksq] : StepAttacksBB[B_KING][bksq]; - } + operator Result() const { return res; } - Bitboard p_attacks() const { return StepAttacksBB[W_PAWN][psq]; } - void decode_index(int idx); + private: + template Bitboard k_attacks() const + { return StepAttacksBB[KING][Us == WHITE ? wksq : bksq]; } + + template Result classify(const std::vector& db); - Square wksq, bksq, psq; Color stm; + Square bksq, wksq, psq; + Result res; }; - // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 - const int IndexMax = 2 * 24 * 64 * 64; // stm * wp_sq * wk_sq * bk_sq = 196608 - - // Each uint32_t stores results of 32 positions, one per bit - uint32_t KPKBitbase[IndexMax / 32]; +} // namespace - int index(Square wksq, Square bksq, Square psq, Color stm); -} +bool Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) { -uint32_t Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) { + assert(file_of(wpsq) <= FILE_D); - int idx = index(wksq, bksq, wpsq, stm); + unsigned idx = index(stm, bksq, wksq, wpsq); return KPKBitbase[idx / 32] & (1 << (idx & 31)); } void Bitbases::init_kpk() { - Result* db = new Result[IndexMax]; // Avoid to hit stack limit on some platforms - KPKPosition pos; - int idx, bit, repeat = 1; + unsigned idx, repeat = 1; + std::vector db(IndexMax); - // Initialize table with known win / draw positions + // Initialize db with known win / draw positions for (idx = 0; idx < IndexMax; idx++) - db[idx] = pos.classify_leaf(idx); + db[idx].classify_leaf(idx); // Iterate until all positions are classified (30 cycles needed) while (repeat) for (repeat = idx = 0; idx < IndexMax; idx++) - if (db[idx] == UNKNOWN && (db[idx] = pos.classify(idx, db)) != UNKNOWN) + if (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN) repeat = 1; - // Map 32 position results into one KPKBitbase[] entry - for (idx = 0; idx < IndexMax / 32; idx++) - for (bit = 0; bit < 32; bit++) - if (db[32 * idx + bit] == WIN) - KPKBitbase[idx] |= 1 << bit; - - delete [] db; + // Map 32 results into one KPKBitbase[] entry + for (idx = 0; idx < IndexMax; idx++) + if (db[idx] == WIN) + KPKBitbase[idx / 32] |= 1 << (idx & 31); } namespace { - // A KPK bitbase index is an integer in [0, IndexMax] range - // - // Information is mapped in this way - // - // bit 0: side to move (WHITE or BLACK) - // bit 1- 6: black king square (from SQ_A1 to SQ_H8) - // bit 7-12: white king square (from SQ_A1 to SQ_H8) - // bit 13-14: white pawn file (from FILE_A to FILE_D) - // bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1) - - int index(Square w, Square b, Square p, Color c) { - - assert(file_of(p) <= FILE_D); - - return c + (b << 1) + (w << 7) + (file_of(p) << 13) + ((rank_of(p) - 1) << 15); - } - - void KPKPosition::decode_index(int idx) { + void KPKPosition::classify_leaf(unsigned idx) { stm = Color(idx & 1); - bksq = Square((idx >> 1) & 63); - wksq = Square((idx >> 7) & 63); + bksq = Square((idx >> 1) & 0x3F); + wksq = Square((idx >> 7) & 0x3F); psq = File((idx >> 13) & 3) | Rank((idx >> 15) + 1); - } - - Result KPKPosition::classify_leaf(int idx) { - - decode_index(idx); // Check if two pieces are on the same square or if a king can be captured if ( wksq == psq || wksq == bksq || bksq == psq || (k_attacks() & bksq) - || (stm == WHITE && (p_attacks() & bksq))) - return INVALID; + || (stm == WHITE && (StepAttacksBB[PAWN][psq] & bksq))) + res = INVALID; // The position is an immediate win if it is white to move and the white // pawn can be promoted without getting captured. - if ( rank_of(psq) == RANK_7 - && stm == WHITE - && wksq != psq + DELTA_N - && ( square_distance(bksq, psq + DELTA_N) > 1 - ||(k_attacks() & (psq + DELTA_N)))) - return WIN; + else if ( rank_of(psq) == RANK_7 + && stm == WHITE + && wksq != psq + DELTA_N + && ( square_distance(bksq, psq + DELTA_N) > 1 + ||(k_attacks() & (psq + DELTA_N)))) + res = WIN; // Check for known draw positions // // Case 1: Stalemate - if ( stm == BLACK - && !(k_attacks() & ~(k_attacks() | p_attacks()))) - return DRAW; + else if ( stm == BLACK + && !(k_attacks() & ~(k_attacks() | StepAttacksBB[PAWN][psq]))) + res = DRAW; // Case 2: King can capture undefended pawn - if ( stm == BLACK - && (k_attacks() & psq & ~k_attacks())) - return DRAW; + else if ( stm == BLACK + && (k_attacks() & psq & ~k_attacks())) + res = DRAW; // Case 3: Black king in front of white pawn - if ( bksq == psq + DELTA_N - && rank_of(psq) < RANK_7) - return DRAW; + else if ( bksq == psq + DELTA_N + && rank_of(psq) < RANK_7) + res = DRAW; // Case 4: White king in front of pawn and black has opposition - if ( stm == WHITE - && wksq == psq + DELTA_N - && bksq == wksq + DELTA_N + DELTA_N - && rank_of(psq) < RANK_5) - return DRAW; + else if ( stm == WHITE + && wksq == psq + DELTA_N + && bksq == wksq + DELTA_N + DELTA_N + && rank_of(psq) < RANK_5) + res = DRAW; // Case 5: Stalemate with rook pawn - if ( bksq == SQ_A8 - && file_of(psq) == FILE_A) - return DRAW; + else if ( bksq == SQ_A8 + && file_of(psq) == FILE_A) + res = DRAW; // Case 6: White king trapped on the rook file - if ( file_of(wksq) == FILE_A - && file_of(psq) == FILE_A - && rank_of(wksq) > rank_of(psq) - && bksq == wksq + 2) - return DRAW; - - return UNKNOWN; + else if ( file_of(wksq) == FILE_A + && file_of(psq) == FILE_A + && rank_of(wksq) > rank_of(psq) + && bksq == wksq + 2) + res = DRAW; + + else + res = UNKNOWN; } template - Result KPKPosition::classify(const Result db[]) const { + Result KPKPosition::classify(const std::vector& db) { // White to Move: If one move leads to a position classified as RESULT_WIN, // the result of the current position is RESULT_WIN. If all moves lead to @@ -198,35 +189,29 @@ namespace { while (b) { - r |= Us == WHITE ? db[index(pop_lsb(&b), bksq, psq, BLACK)] - : db[index(wksq, pop_lsb(&b), psq, WHITE)]; + r |= Us == WHITE ? db[index(BLACK, bksq, pop_lsb(&b), psq)] + : db[index(WHITE, pop_lsb(&b), wksq, psq)]; if (Us == WHITE && (r & WIN)) - return WIN; + return res = WIN; if (Us == BLACK && (r & DRAW)) - return DRAW; + return res = DRAW; } if (Us == WHITE && rank_of(psq) < RANK_7) { Square s = psq + DELTA_N; - r |= db[index(wksq, bksq, s, BLACK)]; // Single push + r |= db[index(BLACK, bksq, wksq, s)]; // Single push if (rank_of(s) == RANK_3 && s != wksq && s != bksq) - r |= db[index(wksq, bksq, s + DELTA_N, BLACK)]; // Double push + r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push if (r & WIN) - return WIN; + return res = WIN; } - return r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN; - } - - Result KPKPosition::classify(int idx, Result db[]) { - - decode_index(idx); - return stm == WHITE ? classify(db) : classify(db); + return res = r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN; } } diff --git a/src/bitboard.h b/src/bitboard.h index 35904377..e3331bd4 100644 --- a/src/bitboard.h +++ b/src/bitboard.h @@ -33,7 +33,7 @@ void print(Bitboard b); namespace Bitbases { void init_kpk(); -uint32_t probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm); +bool probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm); } -- 2.39.2