/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 Marco Costalba
+ Copyright (C) 2008-2010 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
#include <cassert>
#include "bitbase.h"
+#include "bitcount.h"
#include "endgame.h"
-////
-//// Constants and variables
-////
-
-/// Evaluation functions
-
-// Generic "mate lone king" eval
-EvaluationFunction<KXK> EvaluateKXK(WHITE), EvaluateKKX(BLACK);
-
-// K and two minors vs K and one or two minors
-EvaluationFunction<KmmKm> EvaluateKmmKm(WHITE);
-
-EvaluationFunction<KBNK> EvaluateKBNK(WHITE), EvaluateKKBN(BLACK); // KBN vs K
-EvaluationFunction<KPK> EvaluateKPK(WHITE), EvaluateKKP(BLACK); // KP vs K
-EvaluationFunction<KRKP> EvaluateKRKP(WHITE), EvaluateKPKR(BLACK); // KR vs KP
-EvaluationFunction<KRKB> EvaluateKRKB(WHITE), EvaluateKBKR(BLACK); // KR vs KB
-EvaluationFunction<KRKN> EvaluateKRKN(WHITE), EvaluateKNKR(BLACK); // KR vs KN
-EvaluationFunction<KQKR> EvaluateKQKR(WHITE), EvaluateKRKQ(BLACK); // KQ vs KR
-EvaluationFunction<KBBKN> EvaluateKBBKN(WHITE), EvaluateKNKBB(BLACK); // KBB vs KN
-
-
-/// Scaling functions
-
-// KBP vs K
-KBPKScalingFunction ScaleKBPK = KBPKScalingFunction(WHITE);
-KBPKScalingFunction ScaleKKBP = KBPKScalingFunction(BLACK);
-
-// KQ vs KRP
-KQKRPScalingFunction ScaleKQKRP = KQKRPScalingFunction(WHITE);
-KQKRPScalingFunction ScaleKRPKQ = KQKRPScalingFunction(BLACK);
-
-// KRP vs KR
-KRPKRScalingFunction ScaleKRPKR = KRPKRScalingFunction(WHITE);
-KRPKRScalingFunction ScaleKRKRP = KRPKRScalingFunction(BLACK);
-
-// KRPP vs KRP
-KRPPKRPScalingFunction ScaleKRPPKRP = KRPPKRPScalingFunction(WHITE);
-KRPPKRPScalingFunction ScaleKRPKRPP = KRPPKRPScalingFunction(BLACK);
-
-// King and pawns vs king
-KPsKScalingFunction ScaleKPsK = KPsKScalingFunction(WHITE);
-KPsKScalingFunction ScaleKKPs = KPsKScalingFunction(BLACK);
-
-// KBP vs KB
-KBPKBScalingFunction ScaleKBPKB = KBPKBScalingFunction(WHITE);
-KBPKBScalingFunction ScaleKBKBP = KBPKBScalingFunction(BLACK);
-
-// KBP vs KN
-KBPKNScalingFunction ScaleKBPKN = KBPKNScalingFunction(WHITE);
-KBPKNScalingFunction ScaleKNKBP = KBPKNScalingFunction(BLACK);
-
-// KNP vs K
-KNPKScalingFunction ScaleKNPK = KNPKScalingFunction(WHITE);
-KNPKScalingFunction ScaleKKNP = KNPKScalingFunction(BLACK);
-
-// KPKP
-KPKPScalingFunction ScaleKPKPw = KPKPScalingFunction(WHITE);
-KPKPScalingFunction ScaleKPKPb = KPKPScalingFunction(BLACK);
-
-
////
//// Local definitions
////
// the two kings in basic endgames.
const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
- // Bitbase for KP vs K
- uint8_t KPKBitbase[24576];
-
// Penalty for big distance between king and knight for the defending king
// and knight in KR vs KN endgames.
const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 };
+ // Bitbase for KP vs K
+ uint8_t KPKBitbase[24576];
+
// Various inline functions for accessing the above arrays
inline Value mate_table(Square s) {
return Value(MateTable[s]);
//// Functions
////
-/// Constructors
-
-EndgameEvaluationFunction::EndgameEvaluationFunction(Color c) : strongerSide(c) {
- weakerSide = opposite_color(strongerSide);
-}
+/// init_bitbases() is called during program initialization, and simply loads
+/// bitbases from disk into memory. At the moment, there is only the bitbase
+/// for KP vs K, but we may decide to add other bitbases later.
-ScalingFunction::ScalingFunction(Color c) : strongerSide(c) {
- weakerSide = opposite_color(c);
+void init_bitbases() {
+ generate_kpk_bitbase(KPKBitbase);
}
-KBPKScalingFunction::KBPKScalingFunction(Color c) : ScalingFunction(c) {}
-KQKRPScalingFunction::KQKRPScalingFunction(Color c) : ScalingFunction(c) {}
-KRPKRScalingFunction::KRPKRScalingFunction(Color c) : ScalingFunction(c) {}
-KRPPKRPScalingFunction::KRPPKRPScalingFunction(Color c) : ScalingFunction(c) {}
-KPsKScalingFunction::KPsKScalingFunction(Color c) : ScalingFunction(c) {}
-KBPKBScalingFunction::KBPKBScalingFunction(Color c) : ScalingFunction(c) {}
-KBPKNScalingFunction::KBPKNScalingFunction(Color c) : ScalingFunction(c) {}
-KNPKScalingFunction::KNPKScalingFunction(Color c) : ScalingFunction(c) {}
-KPKPScalingFunction::KPKPScalingFunction(Color c) : ScalingFunction(c) {}
-
/// Mate with KX vs K. This function is used to evaluate positions with
/// King and plenty of material vs a lone king. It simply gives the
/// attacking side a bonus for driving the defending king towards the edge
/// of the board, and for keeping the distance between the two kings small.
template<>
-Value EvaluationFunction<KXK>::apply(const Position& pos) {
+Value EvaluationFunction<KXK>::apply(const Position& pos) const {
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- assert(pos.piece_count(weakerSide, PAWN) == Value(0));
+ assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
+ assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
+ mate_table(loserKSq)
+ distance_bonus(square_distance(winnerKSq, loserKSq));
- if ( pos.piece_count(strongerSide, QUEEN) > 0
- || pos.piece_count(strongerSide, ROOK) > 0
+ if ( pos.piece_count(strongerSide, QUEEN)
+ || pos.piece_count(strongerSide, ROOK)
|| pos.piece_count(strongerSide, BISHOP) > 1)
// TODO: check for two equal-colored bishops!
result += VALUE_KNOWN_WIN;
- return (strongerSide == pos.side_to_move() ? result : -result);
+ return strongerSide == pos.side_to_move() ? result : -result;
}
/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
/// defending king towards a corner square of the right color.
template<>
-Value EvaluationFunction<KBNK>::apply(const Position& pos) {
+Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- assert(pos.piece_count(weakerSide, PAWN) == Value(0));
+ assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
+ assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame + BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
Square loserKSq = pos.king_square(weakerSide);
Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
- if (square_color(bishopSquare) == BLACK)
+ // kbnk_mate_table() tries to drive toward corners A1 or H8,
+ // if we have a bishop that cannot reach the above squares we
+ // mirror the kings so to drive enemy toward corners A8 or H1.
+ if (!same_color_squares(bishopSquare, SQ_A1))
{
winnerKSq = flop_square(winnerKSq);
loserKSq = flop_square(loserKSq);
+ distance_bonus(square_distance(winnerKSq, loserKSq))
+ kbnk_mate_table(loserKSq);
- return (strongerSide == pos.side_to_move() ? result : -result);
+ return strongerSide == pos.side_to_move() ? result : -result;
}
/// KP vs K. This endgame is evaluated with the help of a bitbase.
template<>
-Value EvaluationFunction<KPK>::apply(const Position& pos) {
+Value EvaluationFunction<KPK>::apply(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == Value(0));
- assert(pos.non_pawn_material(weakerSide) == Value(0));
+ assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
+ assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(strongerSide, PAWN) == 1);
assert(pos.piece_count(weakerSide, PAWN) == 0);
if (square_file(wpsq) >= FILE_E)
{
- wksq = flop_square(wksq);
- bksq = flop_square(bksq);
- wpsq = flop_square(wpsq);
+ wksq = flop_square(wksq);
+ bksq = flop_square(bksq);
+ wpsq = flop_square(wpsq);
}
if (!probe_kpk(wksq, wpsq, bksq, stm))
+ PawnValueEndgame
+ Value(square_rank(wpsq));
- return (strongerSide == pos.side_to_move() ? result : -result);
+ return strongerSide == pos.side_to_move() ? result : -result;
}
/// far advanced with support of the king, while the attacking king is far
/// away.
template<>
-Value EvaluationFunction<KRKP>::apply(const Position& pos) {
+Value EvaluationFunction<KRKP>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
// If the weaker side's king is too far from the pawn and the rook,
// it's a win
- else if ( square_distance(bksq, bpsq) - (tempo^1) >= 3
+ else if ( square_distance(bksq, bpsq) - (tempo ^ 1) >= 3
&& square_distance(bksq, wrsq) >= 3)
result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+ Value(square_distance(bksq, bpsq + DELTA_S) * 8)
+ Value(square_distance(bpsq, queeningSq) * 8);
- return (strongerSide == pos.side_to_move() ? result : -result);
+ return strongerSide == pos.side_to_move() ? result : -result;
}
/// KR vs KB. This is very simple, and always returns drawish scores. The
/// score is slightly bigger when the defending king is close to the edge.
template<>
-Value EvaluationFunction<KRKB>::apply(const Position& pos) {
+Value EvaluationFunction<KRKB>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.piece_count(weakerSide, BISHOP) == 1);
Value result = mate_table(pos.king_square(weakerSide));
- return (pos.side_to_move() == strongerSide ? result : -result);
+ return strongerSide == pos.side_to_move() ? result : -result;
}
/// KR vs KN. The attacking side has slightly better winning chances than
/// in KR vs KB, particularly if the king and the knight are far apart.
template<>
-Value EvaluationFunction<KRKN>::apply(const Position& pos) {
+Value EvaluationFunction<KRKN>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
Square defendingKSq = pos.king_square(weakerSide);
Square nSq = pos.piece_list(weakerSide, KNIGHT, 0);
- Value result = Value(10) + mate_table(defendingKSq) +
- krkn_king_knight_distance_penalty(square_distance(defendingKSq, nSq));
+ int d = square_distance(defendingKSq, nSq);
+ Value result = Value(10)
+ + mate_table(defendingKSq)
+ + krkn_king_knight_distance_penalty(d);
- return (strongerSide == pos.side_to_move())? result : -result;
+ return strongerSide == pos.side_to_move() ? result : -result;
}
/// for the defending side in the search, this is usually sufficient to be
/// able to win KQ vs KR.
template<>
-Value EvaluationFunction<KQKR>::apply(const Position& pos) {
+Value EvaluationFunction<KQKR>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
+ mate_table(loserKSq)
+ distance_bonus(square_distance(winnerKSq, loserKSq));
- return (strongerSide == pos.side_to_move())? result : -result;
+ return strongerSide == pos.side_to_move() ? result : -result;
}
template<>
-Value EvaluationFunction<KBBKN>::apply(const Position& pos) {
+Value EvaluationFunction<KBBKN>::apply(const Position& pos) const {
assert(pos.piece_count(strongerSide, BISHOP) == 2);
assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
assert(pos.piece_count(weakerSide, KNIGHT) == 1);
assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
- assert(pos.pawns() == EmptyBoardBB);
+ assert(pos.pieces(PAWN) == EmptyBoardBB);
Value result = BishopValueEndgame;
Square wksq = pos.king_square(strongerSide);
result += Value(square_distance(bksq, nsq) * 32);
// Bonus for restricting the knight's mobility
- result += Value((8 - count_1s_max_15(pos.piece_attacks<KNIGHT>(nsq))) * 8);
+ result += Value((8 - count_1s_max_15(pos.attacks_from<KNIGHT>(nsq))) * 8);
- return (strongerSide == pos.side_to_move() ? result : -result);
+ return strongerSide == pos.side_to_move() ? result : -result;
}
+
+/// K and two minors vs K and one or two minors or K and two knights against
+/// king alone are always draw.
template<>
-Value EvaluationFunction<KmmKm>::apply(const Position &pos) {
- return Value(0);
+Value EvaluationFunction<KmmKm>::apply(const Position&) const {
+ return VALUE_ZERO;
}
+template<>
+Value EvaluationFunction<KNNK>::apply(const Position&) const {
+ return VALUE_ZERO;
+}
/// KBPKScalingFunction scales endgames where the stronger side has king,
/// bishop and one or more pawns. It checks for draws with rook pawns and a
-/// bishop of the wrong color. If such a draw is detected, ScaleFactor(0) is
+/// bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_ZERO is
/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
/// will be used.
-
-ScaleFactor KBPKScalingFunction::apply(const Position& pos) {
+template<>
+ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
// No assertions about the material of weakerSide, because we want draws to
// be detected even when the weaker side has some pawns.
- Bitboard pawns = pos.pawns(strongerSide);
+ Bitboard pawns = pos.pieces(PAWN, strongerSide);
File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 0));
// All pawns are on a single rook file ?
Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
Square kingSq = pos.king_square(weakerSide);
- if ( square_color(queeningSq) != square_color(bishopSq)
+ if ( !same_color_squares(queeningSq, bishopSq)
&& file_distance(square_file(kingSq), pawnFile) <= 1)
{
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the neighboring file. Find the rank of the
// frontmost pawn.
-
Rank rank;
if (strongerSide == WHITE)
{
}
else
{
- for(rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
- rank = Rank(rank^7); // HACK to get the relative rank
+ for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
+ rank = Rank(rank ^ 7); // HACK to get the relative rank
assert(rank >= RANK_2 && rank <= RANK_7);
}
// If the defending king has distance 1 to the promotion square or
// is placed somewhere in front of the pawn, it's a draw.
if ( square_distance(kingSq, queeningSq) <= 1
|| relative_rank(strongerSide, kingSq) >= rank)
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
}
}
return SCALE_FACTOR_NONE;
/// king and queen, while the weaker side has at least a rook and a pawn.
/// It tests for fortress draws with a rook on the third rank defended by
/// a pawn.
-
-ScaleFactor KQKRPScalingFunction::apply(const Position& pos) {
+template<>
+ScaleFactor ScalingFunction<KQKRPs>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, QUEEN) == 1);
Square kingSq = pos.king_square(weakerSide);
if ( relative_rank(weakerSide, kingSq) <= RANK_2
&& relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4
- && (pos.rooks(weakerSide) & relative_rank_bb(weakerSide, RANK_3))
- && (pos.pawns(weakerSide) & relative_rank_bb(weakerSide, RANK_2))
- && (pos.piece_attacks<KING>(kingSq) & pos.pawns(weakerSide)))
+ && (pos.pieces(ROOK, weakerSide) & relative_rank_bb(weakerSide, RANK_3))
+ && (pos.pieces(PAWN, weakerSide) & relative_rank_bb(weakerSide, RANK_2))
+ && (pos.attacks_from<KING>(kingSq) & pos.pieces(PAWN, weakerSide)))
{
Square rsq = pos.piece_list(weakerSide, ROOK, 0);
- if (pos.pawn_attacks(strongerSide, rsq) & pos.pawns(weakerSide))
- return ScaleFactor(0);
+ if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(PAWN, weakerSide))
+ return SCALE_FACTOR_ZERO;
}
return SCALE_FACTOR_NONE;
}
///
/// It would also be nice to rewrite the actual code for this function,
/// which is mostly copied from Glaurung 1.x, and not very pretty.
-
-ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
+template<>
+ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 1);
&& square_distance(bksq, queeningSq) <= 1
&& wksq <= SQ_H5
&& (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
&& square_distance(bksq, queeningSq) <= 1
&& square_rank(wksq) + tempo <= RANK_6
&& (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
if ( r >= RANK_6
&& bksq == queeningSq
&& square_rank(brsq) == RANK_1
&& (!tempo || square_distance(wksq, wpsq) >= 2))
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
&& (bksq == SQ_H7 || bksq == SQ_G7)
&& square_file(brsq) == FILE_A
&& (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
&& bksq == wpsq + DELTA_N
&& square_distance(wksq, wpsq) - tempo >= 2
&& square_distance(wksq, brsq) - tempo >= 2)
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
|| ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
&& (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- - (8 * square_distance(wpsq, queeningSq)
- + 2 * square_distance(wksq, queeningSq)));
+ - 8 * square_distance(wpsq, queeningSq)
+ - 2 * square_distance(wksq, queeningSq));
// If the pawn is not far advanced, and the defending king is somewhere in
// the pawn's path, it's probably a draw.
/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
/// single pattern: If the stronger side has no pawns and the defending king
/// is actively placed, the position is drawish.
-
-ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
+template<>
+ScaleFactor ScalingFunction<KRPPKRP>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 2);
/// KPsKScalingFunction scales endgames with king and two or more pawns
/// against king. There is just a single rule here: If all pawns are on
/// the same rook file and are blocked by the defending king, it's a draw.
+template<>
+ScaleFactor ScalingFunction<KPsK>::apply(const Position& pos) const {
-ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
-
- assert(pos.non_pawn_material(strongerSide) == Value(0));
+ assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
assert(pos.piece_count(strongerSide, PAWN) >= 2);
- assert(pos.non_pawn_material(weakerSide) == Value(0));
+ assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == 0);
- Bitboard pawns = pos.pawns(strongerSide);
+ Square ksq = pos.king_square(weakerSide);
+ Bitboard pawns = pos.pieces(PAWN, strongerSide);
// Are all pawns on the 'a' file?
if ((pawns & ~FileABB) == EmptyBoardBB)
{
// Does the defending king block the pawns?
- Square ksq = pos.king_square(weakerSide);
- if (square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
- return ScaleFactor(0);
- else if( square_file(ksq) == FILE_A
- && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
- return ScaleFactor(0);
- else
- return SCALE_FACTOR_NONE;
+ if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
+ || ( square_file(ksq) == FILE_A
+ && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
+ return SCALE_FACTOR_ZERO;
}
// Are all pawns on the 'h' file?
else if ((pawns & ~FileHBB) == EmptyBoardBB)
{
// Does the defending king block the pawns?
- Square ksq = pos.king_square(weakerSide);
- if (square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
- return ScaleFactor(0);
- else if ( square_file(ksq) == FILE_H
- && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
- return ScaleFactor(0);
- else
- return SCALE_FACTOR_NONE;
+ if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
+ || ( square_file(ksq) == FILE_H
+ && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
+ return SCALE_FACTOR_ZERO;
}
- else
- return SCALE_FACTOR_NONE;
+ return SCALE_FACTOR_NONE;
}
/// square of the king is not of the same color as the stronger side's bishop,
/// it's a draw. If the two bishops have opposite color, it's almost always
/// a draw.
-
-ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
+template<>
+ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
// Case 1: Defending king blocks the pawn, and cannot be driven away
if ( square_file(weakerKingSq) == square_file(pawnSq)
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( square_color(weakerKingSq) != square_color(strongerBishopSq)
+ && ( !same_color_squares(weakerKingSq, strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
// Case 2: Opposite colored bishops
- if (square_color(strongerBishopSq) != square_color(weakerBishopSq))
+ if (!same_color_squares(strongerBishopSq, weakerBishopSq))
{
// We assume that the position is drawn in the following three situations:
//
// reasonably well.
if (relative_rank(strongerSide, pawnSq) <= RANK_5)
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
else
{
Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
- if (ray & pos.kings(weakerSide))
- return ScaleFactor(0);
- if( (pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
- return ScaleFactor(0);
+ if (ray & pos.pieces(KING, weakerSide))
+ return SCALE_FACTOR_ZERO;
+
+ if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & ray)
+ && square_distance(weakerBishopSq, pawnSq) >= 3)
+ return SCALE_FACTOR_ZERO;
}
}
return SCALE_FACTOR_NONE;
}
+/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic
+/// draws with opposite-colored bishops.
+template<>
+ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
+
+ assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
+ assert(pos.piece_count(strongerSide, BISHOP) == 1);
+ assert(pos.piece_count(strongerSide, PAWN) == 2);
+ assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
+ assert(pos.piece_count(weakerSide, BISHOP) == 1);
+ assert(pos.piece_count(weakerSide, PAWN) == 0);
+
+ Square wbsq = pos.piece_list(strongerSide, BISHOP, 0);
+ Square bbsq = pos.piece_list(weakerSide, BISHOP, 0);
+
+ if (same_color_squares(wbsq, bbsq))
+ // Not opposite-colored bishops, no scaling
+ return SCALE_FACTOR_NONE;
+
+ Square ksq = pos.king_square(weakerSide);
+ Square psq1 = pos.piece_list(strongerSide, PAWN, 0);
+ Square psq2 = pos.piece_list(strongerSide, PAWN, 1);
+ Rank r1 = square_rank(psq1);
+ Rank r2 = square_rank(psq2);
+ Square blockSq1, blockSq2;
+
+ if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
+ {
+ blockSq1 = psq1 + pawn_push(strongerSide);
+ blockSq2 = make_square(square_file(psq2), square_rank(psq1));
+ }
+ else
+ {
+ blockSq1 = psq2 + pawn_push(strongerSide);
+ blockSq2 = make_square(square_file(psq1), square_rank(psq2));
+ }
+
+ switch (file_distance(psq1, psq2))
+ {
+ case 0:
+ // Both pawns are on the same file. Easy draw if defender firmly controls
+ // some square in the frontmost pawn's path.
+ if ( square_file(ksq) == square_file(blockSq1)
+ && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
+ && !same_color_squares(ksq, wbsq))
+ return SCALE_FACTOR_ZERO;
+ else
+ return SCALE_FACTOR_NONE;
+
+ case 1:
+ // Pawns on neighboring files. Draw if defender firmly controls the square
+ // in front of the frontmost pawn's path, and the square diagonally behind
+ // this square on the file of the other pawn.
+ if ( ksq == blockSq1
+ && !same_color_squares(ksq, wbsq)
+ && ( bbsq == blockSq2
+ || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
+ || rank_distance(r1, r2) >= 2))
+ return SCALE_FACTOR_ZERO;
+
+ else if ( ksq == blockSq2
+ && !same_color_squares(ksq, wbsq)
+ && ( bbsq == blockSq1
+ || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
+ return SCALE_FACTOR_ZERO;
+ else
+ return SCALE_FACTOR_NONE;
+
+ default:
+ // The pawns are not on the same file or adjacent files. No scaling.
+ return SCALE_FACTOR_NONE;
+ }
+}
+
+
/// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule:
/// If the defending king is somewhere along the path of the pawn, and the
/// square of the king is not of the same color as the stronger side's bishop,
/// it's a draw.
-
-ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
+template<>
+ScaleFactor ScalingFunction<KBPKN>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
assert(pos.piece_count(strongerSide, BISHOP) == 1);
if ( square_file(weakerKingSq) == square_file(pawnSq)
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( square_color(weakerKingSq) != square_color(strongerBishopSq)
+ && ( !same_color_squares(weakerKingSq, strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
return SCALE_FACTOR_NONE;
}
/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule:
/// If the pawn is a rook pawn on the 7th rank and the defending king prevents
/// the pawn from advancing, the position is drawn.
-
-ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
+template<>
+ScaleFactor ScalingFunction<KNPK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == Value(0));
+ assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == 0);
Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
if ( pawnSq == relative_square(strongerSide, SQ_A7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
if ( pawnSq == relative_square(strongerSide, SQ_H7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
- return ScaleFactor(0);
+ return SCALE_FACTOR_ZERO;
return SCALE_FACTOR_NONE;
}
/// the pawn as well. The exception is when the stronger side's pawn is far
/// advanced and not on a rook file; in this case it is often possible to win
/// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
+template<>
+ScaleFactor ScalingFunction<KPKP>::apply(const Position& pos) const {
-ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
-
- assert(pos.non_pawn_material(strongerSide) == Value(0));
- assert(pos.non_pawn_material(weakerSide) == Value(0));
+ assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
+ assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(WHITE, PAWN) == 1);
assert(pos.piece_count(BLACK, PAWN) == 1);
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a
// draw, it's probably at least a draw even with the pawn.
- if (probe_kpk(wksq, wpsq, bksq, stm))
- return SCALE_FACTOR_NONE;
- else
- return ScaleFactor(0);
-}
-
-
-/// init_bitbases() is called during program initialization, and simply loads
-/// bitbases from disk into memory. At the moment, there is only the bitbase
-/// for KP vs K, but we may decide to add other bitbases later.
-
-void init_bitbases() {
- generate_kpk_bitbase(KPKBitbase);
+ return probe_kpk(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO;
}
namespace {
- // Probe the KP vs K bitbase:
+ // Probe the KP vs K bitbase
int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) {
- int wp = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4;
- int index = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*wp;
+ int wp = square_file(wpsq) + 4 * (square_rank(wpsq) - 1);
+ int index = int(stm) + 2 * bksq + 128 * wksq + 8192 * wp;
+
+ assert(index >= 0 && index < 24576 * 8);
- assert(index >= 0 && index < 24576*8);
- return KPKBitbase[index/8] & (1 << (index&7));
+ return KPKBitbase[index / 8] & (1 << (index & 7));
}
}
projects / stockfish / blobdiff