/*
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
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 13-14: white pawn file (from FILE_A to FILE_D)
// 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) + ((RANK_7 - rank_of(psq)) << 15);
+ return wksq | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
}
enum Result {
struct KPKPosition {
- operator Result() const { return res; }
- Result classify_leaf(unsigned idx);
+ KPKPosition(unsigned idx);
+ operator Result() const { return result; }
Result classify(const std::vector<KPKPosition>& db)
{ return us == WHITE ? classify<WHITE>(db) : classify<BLACK>(db); }
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;
+ db.reserve(MAX_INDEX);
// Initialize db with known win / draw positions
- for (idx = 0; idx < IndexMax; idx++)
- db[idx].classify_leaf(idx);
+ for (idx = 0; idx < MAX_INDEX; ++idx)
+ db.push_back(KPKPosition(idx));
- // 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;
+ for (repeat = idx = 0; idx < MAX_INDEX; ++idx)
+ repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
// Map 32 results into one KPKBitbase[] entry
- for (idx = 0; idx < IndexMax; idx++)
+ for (idx = 0; idx < MAX_INDEX; ++idx)
if (db[idx] == WIN)
KPKBitbase[idx / 32] |= 1 << (idx & 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) & 0x03) | Rank(RANK_7 - (idx >> 15));
+ 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);
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;
+ return result = r & WIN ? WIN : r & UNKNOWN ? UNKNOWN : DRAW;
else
- return res = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
+ return result = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
}
} // namespace
projects / stockfish / blobdiff