/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2015 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
+#include <numeric>
#include <vector>
#include "bitboard.h"
namespace {
- // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7
- const unsigned IndexMax = 2*24*64*64; // stm * psq * wksq * bksq = 196608
+ // There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7
+ const unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
// Each uint32_t stores results of 32 positions, one per bit
- uint32_t KPKBitbase[IndexMax / 32];
+ uint32_t KPKBitbase[MAX_INDEX / 32];
// A KPK bitbase index is an integer in [0, IndexMax] range
//
- // Information is mapped in a way that minimizes number of iterations:
+ // Information is mapped in a way that minimizes the number of iterations:
//
// bit 0- 5: white king square (from SQ_A1 to SQ_H8)
// bit 6-11: black king square (from SQ_A1 to SQ_H8)
// bit 12: side to move (WHITE or BLACK)
// bit 13-14: white pawn file (from FILE_A to FILE_D)
- // bit 15-17: white pawn 6 - rank (from 6 - RANK_7 to 6 - RANK_2)
+ // bit 15-17: white pawn RANK_7 - rank (from RANK_7 - RANK_7 to RANK_7 - RANK_2)
unsigned index(Color us, Square bksq, Square wksq, Square psq) {
- return wksq + (bksq << 6) + (us << 12) + (file_of(psq) << 13) + ((6 - rank_of(psq)) << 15);
+ return wksq | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
}
enum Result {
inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
struct KPKPosition {
-
- operator Result() const { return res; }
- Result classify_leaf(unsigned idx);
+ KPKPosition() = default;
+ KPKPosition(unsigned idx);
+ operator Result() const { return result; }
Result classify(const std::vector<KPKPosition>& db)
{ return us == WHITE ? classify<WHITE>(db) : classify<BLACK>(db); }
- private:
template<Color Us> Result classify(const std::vector<KPKPosition>& db);
+ unsigned id;
Color us;
Square bksq, wksq, psq;
- Result res;
+ Result result;
};
} // namespace
-bool Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color us) {
+bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) {
assert(file_of(wpsq) <= FILE_D);
}
-void Bitbases::init_kpk() {
+void Bitbases::init() {
- unsigned idx, repeat = 1;
- std::vector<KPKPosition> db(IndexMax);
+ std::vector<KPKPosition> db(MAX_INDEX);
// Initialize db with known win / draw positions
- for (idx = 0; idx < IndexMax; idx++)
- db[idx].classify_leaf(idx);
+ std::generate(db.begin(), db.end(), [](){ static unsigned id; return KPKPosition(id++); });
- // Iterate through the positions until no more of the unknown positions can be
+ // Iterate through the positions until none of the unknown positions can be
// changed to either wins or draws (15 cycles needed).
- while (repeat)
- for (repeat = idx = 0; idx < IndexMax; idx++)
- if (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN)
- repeat = 1;
+ while (std::accumulate(db.begin(), db.end(), false, [&](bool repeat, KPKPosition& pos)
+ { return (pos == UNKNOWN && pos.classify(db) != UNKNOWN) || repeat; }));
// Map 32 results into one KPKBitbase[] entry
- for (idx = 0; idx < IndexMax; idx++)
- if (db[idx] == WIN)
- KPKBitbase[idx / 32] |= 1 << (idx & 0x1F);
+ for (auto& pos : db)
+ if (pos == WIN)
+ KPKBitbase[pos.id / 32] |= 1 << (pos.id & 0x1F);
}
namespace {
- Result KPKPosition::classify_leaf(unsigned idx) {
+ KPKPosition::KPKPosition(unsigned idx) {
- wksq = Square((idx >> 0) & 0x3F);
- bksq = Square((idx >> 6) & 0x3F);
- us = Color((idx >> 12) & 0x01);
- psq = File((idx >> 13) & 3) | Rank(6 - (idx >> 15));
+ id = idx;
+ wksq = Square((idx >> 0) & 0x3F);
+ bksq = Square((idx >> 6) & 0x3F);
+ us = Color ((idx >> 12) & 0x01);
+ psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
+ result = UNKNOWN;
// Check if two pieces are on the same square or if a king can be captured
- if ( wksq == psq || wksq == bksq || bksq == psq
- || (StepAttacksBB[KING][wksq] & bksq)
+ if ( distance(wksq, bksq) <= 1
+ || wksq == psq
+ || bksq == psq
|| (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq)))
- return res = INVALID;
+ result = INVALID;
- if (us == WHITE)
+ else if (us == WHITE)
{
- // Immediate win if pawn can be promoted without getting captured
+ // Immediate win if a pawn can be promoted without getting captured
if ( rank_of(psq) == RANK_7
&& wksq != psq + DELTA_N
- && ( square_distance(bksq, psq + DELTA_N) > 1
+ && ( distance(bksq, psq + DELTA_N) > 1
||(StepAttacksBB[KING][wksq] & (psq + DELTA_N))))
- return res = WIN;
+ result = WIN;
}
- // Immediate draw if is stalemate or king captures undefended pawn
+ // Immediate draw if it is a stalemate or a king captures undefended pawn
else if ( !(StepAttacksBB[KING][bksq] & ~(StepAttacksBB[KING][wksq] | StepAttacksBB[PAWN][psq]))
|| (StepAttacksBB[KING][bksq] & psq & ~StepAttacksBB[KING][wksq]))
- return res = DRAW;
-
- return res = UNKNOWN;
+ result = DRAW;
}
template<Color Us>
// White to Move: If one move leads to a position classified as WIN, the result
// of the current position is WIN. If all moves lead to positions classified
- // as DRAW, the current position is classified DRAW otherwise the current
+ // as DRAW, the current position is classified as DRAW, otherwise the current
// position is classified as UNKNOWN.
//
// Black to Move: If one move leads to a position classified as DRAW, the result
// of the current position is DRAW. If all moves lead to positions classified
- // as WIN, the position is classified WIN otherwise the current position is
- // classified UNKNOWN.
+ // as WIN, the position is classified as WIN, otherwise the current position is
+ // classified as UNKNOWN.
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Result Good = (Us == WHITE ? WIN : DRAW);
+ const Result Bad = (Us == WHITE ? DRAW : WIN);
Result r = INVALID;
Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq];
Square s = psq + DELTA_N;
r |= db[index(BLACK, bksq, wksq, s)]; // Single push
- if (rank_of(s) == RANK_3 && s != wksq && s != bksq)
+ if (rank_of(psq) == RANK_2 && s != wksq && s != bksq)
r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push
}
- if (Us == WHITE)
- return res = r & WIN ? WIN : r & UNKNOWN ? UNKNOWN : DRAW;
- else
- return res = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
+ return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad;
}
} // namespace
projects / stockfish / blobdiff