along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
+#include <numeric>
#include <vector>
#include "bitboard.h"
inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
struct KPKPosition {
-
- KPKPosition(unsigned idx);
+ KPKPosition() = default;
+ explicit 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;
+ Square ksq[COLOR_NB], psq;
Result result;
};
void Bitbases::init() {
- unsigned idx, repeat = 1;
- std::vector<KPKPosition> db;
- db.reserve(MAX_INDEX);
+ std::vector<KPKPosition> db(MAX_INDEX);
// Initialize db with known win / draw positions
- for (idx = 0; idx < MAX_INDEX; ++idx)
- db.push_back(KPKPosition(idx));
+ std::generate(db.begin(), db.end(), [](){ static unsigned id; return KPKPosition(id++); });
// 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 < MAX_INDEX; ++idx)
- repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
+ 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 < MAX_INDEX; ++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);
}
KPKPosition::KPKPosition(unsigned 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;
+ id = idx;
+ ksq[WHITE] = Square((idx >> 0) & 0x3F);
+ ksq[BLACK] = Square((idx >> 6) & 0x3F);
+ us = Color ((idx >> 12) & 0x01);
+ psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
// Check if two pieces are on the same square or if a king can be captured
- if ( distance(wksq, bksq) <= 1
- || wksq == psq
- || bksq == psq
- || (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq)))
+ if ( distance(ksq[WHITE], ksq[BLACK]) <= 1
+ || ksq[WHITE] == psq
+ || ksq[BLACK] == psq
+ || (us == WHITE && (StepAttacksBB[PAWN][psq] & ksq[BLACK])))
result = INVALID;
- else if (us == WHITE)
- {
- // Immediate win if a pawn can be promoted without getting captured
- if ( rank_of(psq) == RANK_7
- && wksq != psq + DELTA_N
- && ( distance(bksq, psq + DELTA_N) > 1
- ||(StepAttacksBB[KING][wksq] & (psq + DELTA_N))))
- result = WIN;
- }
+ // Immediate win if a pawn can be promoted without getting captured
+ else if ( us == WHITE
+ && rank_of(psq) == RANK_7
+ && ksq[us] != psq + DELTA_N
+ && ( distance(ksq[~us], psq + DELTA_N) > 1
+ || (StepAttacksBB[KING][ksq[us]] & (psq + DELTA_N))))
+ result = WIN;
+
// 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]))
+ else if ( us == BLACK
+ && ( !(StepAttacksBB[KING][ksq[us]] & ~(StepAttacksBB[KING][ksq[~us]] | StepAttacksBB[PAWN][psq]))
+ || (StepAttacksBB[KING][ksq[us]] & psq & ~StepAttacksBB[KING][ksq[~us]])))
result = DRAW;
+
+ // Position will be classified later
+ else
+ result = UNKNOWN;
}
template<Color Us>
Result KPKPosition::classify(const std::vector<KPKPosition>& db) {
- // White to Move: If one move leads to a position classified as WIN, the result
+ // 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 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
+ // 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 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];
+ Bitboard b = StepAttacksBB[KING][ksq[Us]];
while (b)
- r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)]
- : db[index(Them, pop_lsb(&b), wksq, psq)];
+ r |= Us == WHITE ? db[index(Them, ksq[Them] , pop_lsb(&b), psq)]
+ : db[index(Them, pop_lsb(&b), ksq[Them] , psq)];
- if (Us == WHITE && rank_of(psq) < RANK_7)
+ if (Us == WHITE)
{
- Square s = psq + DELTA_N;
- r |= db[index(BLACK, bksq, wksq, s)]; // Single push
+ if (rank_of(psq) < RANK_7) // Single push
+ r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N)];
- if (rank_of(psq) == RANK_2 && s != wksq && s != bksq)
- r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push
+ if ( rank_of(psq) == RANK_2 // Double push
+ && psq + DELTA_N != ksq[Us]
+ && psq + DELTA_N != ksq[Them])
+ r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N + DELTA_N)];
}
- if (Us == WHITE)
- return result = r & WIN ? WIN : r & UNKNOWN ? UNKNOWN : DRAW;
- else
- return result = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
+ return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad;
}
} // namespace
projects / stockfish / blobdiff