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Triviality in endgame.cpp

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No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2010-07-17 14:00:25 +01:00
parent a6dcaa575f
commit 53bbcb78d5
1 changed files with 73 additions and 79 deletions
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152
src/endgame.cpp
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@ -65,13 +65,13 @@ namespace {
// 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]);
@ -99,6 +99,15 @@ namespace {
//// Functions
////
/// 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);
}
/// 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
@ -117,13 +126,13 @@ Value EvaluationFunction<KXK>::apply(const Position& pos) const {
+ 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;
}
@ -153,7 +162,7 @@ Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
+ 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;
}
@ -186,9 +195,9 @@ Value EvaluationFunction<KPK>::apply(const Position& pos) const {
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))
@ -198,7 +207,7 @@ Value EvaluationFunction<KPK>::apply(const Position& pos) const {
+ PawnValueEndgame
+ Value(square_rank(wpsq));
return (strongerSide == pos.side_to_move() ? result : -result);
return strongerSide == pos.side_to_move() ? result : -result;
}
@ -239,7 +248,7 @@ Value EvaluationFunction<KRKP>::apply(const Position& pos) const {
// 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));
@ -257,7 +266,7 @@ Value EvaluationFunction<KRKP>::apply(const Position& pos) const {
+ 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;
}
@ -273,7 +282,7 @@ Value EvaluationFunction<KRKB>::apply(const Position& pos) const {
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;
}
@ -291,10 +300,12 @@ Value EvaluationFunction<KRKN>::apply(const Position& pos) const {
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;
}
@ -319,7 +330,7 @@ Value EvaluationFunction<KQKR>::apply(const Position& pos) const {
+ 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<>
@ -345,7 +356,7 @@ Value EvaluationFunction<KBBKN>::apply(const Position& pos) const {
// Bonus for restricting the knight's mobility
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;
}
@ -363,7 +374,7 @@ Value EvaluationFunction<KNNK>::apply(const Position&) const {
/// 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.
template<>
@ -401,15 +412,15 @@ ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) const {
}
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;
@ -438,7 +449,7 @@ ScaleFactor ScalingFunction<KQKRPs>::apply(const Position& pos) const {
{
Square rsq = pos.piece_list(weakerSide, ROOK, 0);
if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(PAWN, weakerSide))
return ScaleFactor(0);
return SCALE_FACTOR_ZERO;
}
return SCALE_FACTOR_NONE;
}
@ -495,7 +506,7 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
&& 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.
@ -503,13 +514,13 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
&& 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.
@ -518,7 +529,7 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
&& (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.
@ -526,7 +537,7 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
&& 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,
@ -549,8 +560,8 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
|| ( 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.
@ -616,36 +627,28 @@ ScaleFactor ScalingFunction<KPsK>::apply(const Position& pos) const {
assert(pos.non_pawn_material(weakerSide) == Value(0));
assert(pos.piece_count(weakerSide, PAWN) == 0);
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;
}
@ -674,7 +677,7 @@ ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& ( square_color(weakerKingSq) != square_color(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))
@ -690,15 +693,16 @@ ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
// 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.pieces(KING, weakerSide))
return ScaleFactor(0);
if( (pos.attacks_from<BISHOP>(weakerBishopSq) & ray)
&& square_distance(weakerBishopSq, pawnSq) >= 3)
return ScaleFactor(0);
return SCALE_FACTOR_ZERO;
if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & ray)
&& square_distance(weakerBishopSq, pawnSq) >= 3)
return SCALE_FACTOR_ZERO;
}
}
return SCALE_FACTOR_NONE;
@ -750,7 +754,7 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
if ( square_file(ksq) == square_file(blockSq1)
&& relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
&& square_color(ksq) != square_color(wbsq))
return ScaleFactor(0);
return SCALE_FACTOR_ZERO;
else
return SCALE_FACTOR_NONE;
@ -763,12 +767,13 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
&& ( bbsq == blockSq2
|| (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
|| rank_distance(r1, r2) >= 2))
return ScaleFactor(0);
return SCALE_FACTOR_ZERO;
else if ( ksq == blockSq2
&& square_color(ksq) != square_color(wbsq)
&& ( bbsq == blockSq1
|| (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
return ScaleFactor(0);
return SCALE_FACTOR_ZERO;
else
return SCALE_FACTOR_NONE;
@ -801,7 +806,7 @@ ScaleFactor ScalingFunction<KBPKN>::apply(const Position& pos) const {
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& ( square_color(weakerKingSq) != square_color(strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
return ScaleFactor(0);
return SCALE_FACTOR_ZERO;
return SCALE_FACTOR_NONE;
}
@ -824,11 +829,11 @@ ScaleFactor ScalingFunction<KNPK>::apply(const Position& pos) const {
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;
}
@ -881,32 +886,21 @@ ScaleFactor ScalingFunction<KPKP>::apply(const Position& pos) const {
// 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);
return KPKBitbase[index/8] & (1 << (index&7));
assert(index >= 0 && index < 24576 * 8);
return KPKBitbase[index / 8] & (1 << (index & 7));
}
}