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Make endgames consistent

Browse source 
Changes variable names and occasionally consolidated variable declarations.
Piece squares are consistently prefixed with "weak" or "strong."

passed STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 29008 W: 5532 L: 5416 D: 18060
Ptnml(0-2): 355, 2983, 7723, 3077, 366
https://tests.stockfishchess.org/tests/view/5eea88d3563bc7aa75600689

closes https://github.com/official-stockfish/Stockfish/pull/2752

No functional change
This commit is contained in:
protonspring 2020-06-17 15:15:54 -06:00 • committed by Joost VandeVondele
parent 6f15e7fab2
commit 8a3f155b1c
1 changed files with 194 additions and 190 deletions
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384
src/endgame.cpp
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@ -28,12 +28,14 @@ namespace {
// Used to drive the king towards the edge of the board
// in KX vs K and KQ vs KR endgames.
// Values range from 27 (center squares) to 90 (in the corners)
inline int push_to_edge(Square s) {
int rd = edge_distance(rank_of(s)), fd = edge_distance(file_of(s));
return 90 - (7 * fd * fd / 2 + 7 * rd * rd / 2);
}
// Used to drive the king towards A1H8 corners in KBN vs K endgames.
// Values range from 0 on A8H1 diagonal to 7 in A1H8 corners
inline int push_to_corner(Square s) {
return abs(7 - rank_of(s) - file_of(s));
}
@ -103,13 +105,13 @@ Value Endgame<KXK>::operator()(const Position& pos) const {
if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
return VALUE_DRAW;
Square winnerKSq = pos.square<KING>(strongSide);
Square loserKSq = pos.square<KING>(weakSide);
Square strongKing = pos.square<KING>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
Value result = pos.non_pawn_material(strongSide)
+ pos.count<PAWN>(strongSide) * PawnValueEg
+ push_to_edge(loserKSq)
+ push_close(winnerKSq, loserKSq);
+ push_to_edge(weakKing)
+ push_close(strongKing, weakKing);
if ( pos.count<QUEEN>(strongSide)
|| pos.count<ROOK>(strongSide)
@ -130,16 +132,16 @@ Value Endgame<KBNK>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
Square winnerKSq = pos.square<KING>(strongSide);
Square loserKSq = pos.square<KING>(weakSide);
Square bishopSq = pos.square<BISHOP>(strongSide);
Square strongKing = pos.square<KING>(strongSide);
Square strongBishop = pos.square<BISHOP>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
// If our bishop does not attack A1/H8, we flip the enemy king square
// to drive to opposite corners (A8/H1).
Value result = (VALUE_KNOWN_WIN + 3520)
+ push_close(winnerKSq, loserKSq)
+ 420 * push_to_corner(opposite_colors(bishopSq, SQ_A1) ? flip_file(loserKSq) : loserKSq);
+ push_close(strongKing, weakKing)
+ 420 * push_to_corner(opposite_colors(strongBishop, SQ_A1) ? flip_file(weakKing) : weakKing);
assert(abs(result) < VALUE_TB_WIN_IN_MAX_PLY);
return strongSide == pos.side_to_move() ? result : -result;
@ -154,16 +156,16 @@ Value Endgame<KPK>::operator()(const Position& pos) const {
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.square<KING>(strongSide));
Square bksq = normalize(pos, strongSide, pos.square<KING>(weakSide));
Square psq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
Square strongKing = normalize(pos, strongSide, pos.square<KING>(strongSide));
Square strongPawn = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
Square weakKing = normalize(pos, strongSide, pos.square<KING>(weakSide));
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
if (!Bitbases::probe(wksq, psq, bksq, us))
if (!Bitbases::probe(strongKing, strongPawn, weakKing, us))
return VALUE_DRAW;
Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq));
Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(strongPawn));
return strongSide == pos.side_to_move() ? result : -result;
}
@ -179,36 +181,35 @@ Value Endgame<KRKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
Square wksq = relative_square(strongSide, pos.square<KING>(strongSide));
Square bksq = relative_square(strongSide, pos.square<KING>(weakSide));
Square rsq = relative_square(strongSide, pos.square<ROOK>(strongSide));
Square psq = relative_square(strongSide, pos.square<PAWN>(weakSide));
Square queeningSq = make_square(file_of(psq), RANK_1);
Square strongKing = relative_square(strongSide, pos.square<KING>(strongSide));
Square weakKing = relative_square(strongSide, pos.square<KING>(weakSide));
Square strongRook = relative_square(strongSide, pos.square<ROOK>(strongSide));
Square weakPawn = relative_square(strongSide, pos.square<PAWN>(weakSide));
Square queeningSquare = make_square(file_of(weakPawn), RANK_1);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
if (forward_file_bb(WHITE, wksq) & psq)
result = RookValueEg - distance(wksq, psq);
if (forward_file_bb(WHITE, strongKing) & weakPawn)
result = RookValueEg - distance(strongKing, weakPawn);
// If the weaker side's king is too far from the pawn and the rook,
// it's a win.
else if ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
&& distance(bksq, rsq) >= 3)
result = RookValueEg - distance(wksq, psq);
else if ( distance(weakKing, weakPawn) >= 3 + (pos.side_to_move() == weakSide)
&& distance(weakKing, strongRook) >= 3)
result = RookValueEg - distance(strongKing, weakPawn);
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
else if ( rank_of(bksq) <= RANK_3
&& distance(bksq, psq) == 1
&& rank_of(wksq) >= RANK_4
&& distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
result = Value(80) - 8 * distance(wksq, psq);
else if ( rank_of(weakKing) <= RANK_3
&& distance(weakKing, weakPawn) == 1
&& rank_of(strongKing) >= RANK_4
&& distance(strongKing, weakPawn) > 2 + (pos.side_to_move() == strongSide))
result = Value(80) - 8 * distance(strongKing, weakPawn);
else
result = Value(200) - 8 * ( distance(wksq, psq + SOUTH)
- distance(bksq, psq + SOUTH)
- distance(psq, queeningSq));
result = Value(200) - 8 * ( distance(strongKing, weakPawn + SOUTH)
- distance(weakKing, weakPawn + SOUTH)
- distance(weakPawn, queeningSquare));
return strongSide == pos.side_to_move() ? result : -result;
}
@ -235,9 +236,9 @@ Value Endgame<KRKN>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
Square bksq = pos.square<KING>(weakSide);
Square bnsq = pos.square<KNIGHT>(weakSide);
Value result = Value(push_to_edge(bksq) + push_away(bksq, bnsq));
Square weakKing = pos.square<KING>(weakSide);
Square weakKnight = pos.square<KNIGHT>(weakSide);
Value result = Value(push_to_edge(weakKing) + push_away(weakKing, weakKnight));
return strongSide == pos.side_to_move() ? result : -result;
}
@ -252,15 +253,15 @@ Value Endgame<KQKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
Square winnerKSq = pos.square<KING>(strongSide);
Square loserKSq = pos.square<KING>(weakSide);
Square pawnSq = pos.square<PAWN>(weakSide);
Square strongKing = pos.square<KING>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
Square weakPawn = pos.square<PAWN>(weakSide);
Value result = Value(push_close(winnerKSq, loserKSq));
Value result = Value(push_close(strongKing, weakKing));
if ( relative_rank(weakSide, pawnSq) != RANK_7
|| distance(loserKSq, pawnSq) != 1
|| ((FileBBB | FileDBB | FileEBB | FileGBB) & pawnSq))
if ( relative_rank(weakSide, weakPawn) != RANK_7
|| distance(weakKing, weakPawn) != 1
|| ((FileBBB | FileDBB | FileEBB | FileGBB) & weakPawn))
result += QueenValueEg - PawnValueEg;
return strongSide == pos.side_to_move() ? result : -result;
@ -277,13 +278,13 @@ Value Endgame<KQKR>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, RookValueMg, 0));
Square winnerKSq = pos.square<KING>(strongSide);
Square loserKSq = pos.square<KING>(weakSide);
Square strongKing = pos.square<KING>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
Value result = QueenValueEg
- RookValueEg
+ push_to_edge(loserKSq)
+ push_close(winnerKSq, loserKSq);
+ push_to_edge(weakKing)
+ push_close(strongKing, weakKing);
return strongSide == pos.side_to_move() ? result : -result;
}
@ -297,9 +298,12 @@ Value Endgame<KNNKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
Square weakKing = pos.square<KING>(weakSide);
Square weakPawn = pos.square<PAWN>(weakSide);
Value result = PawnValueEg
+ 2 * push_to_edge(pos.square<KING>(weakSide))
- 10 * relative_rank(weakSide, pos.square<PAWN>(weakSide));
+ 2 * push_to_edge(weakKing)
- 10 * relative_rank(weakSide, weakPawn);
return strongSide == pos.side_to_move() ? result : -result;
}
@ -325,15 +329,17 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
Bitboard strongPawns = pos.pieces(strongSide, PAWN);
Bitboard allPawns = pos.pieces(PAWN);
Square strongBishop = pos.square<BISHOP>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
Square strongKing = pos.square<KING>(strongSide);
// All strongSide pawns are on a single rook file?
if (!(strongPawns & ~FileABB) || !(strongPawns & ~FileHBB))
{
Square bishopSq = pos.square<BISHOP>(strongSide);
Square queeningSq = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8));
Square weakKingSq = pos.square<KING>(weakSide);
Square queeningSquare = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8));
if ( opposite_colors(queeningSq, bishopSq)
&& distance(queeningSq, weakKingSq) <= 1)
if ( opposite_colors(queeningSquare, strongBishop)
&& distance(queeningSquare, weakKing) <= 1)
return SCALE_FACTOR_DRAW;
}
@ -343,20 +349,16 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
&& pos.count<PAWN>(weakSide) >= 1)
{
// Get the least advanced weakSide pawn
Square weakPawnSq = frontmost_sq(strongSide, pos.pieces(weakSide, PAWN));
Square strongKingSq = pos.square<KING>(strongSide);
Square weakKingSq = pos.square<KING>(weakSide);
Square bishopSq = pos.square<BISHOP>(strongSide);
Square weakPawn = frontmost_sq(strongSide, pos.pieces(weakSide, PAWN));
// There's potential for a draw if our pawn is blocked on the 7th rank,
// the bishop cannot attack it or they only have one pawn left
if ( relative_rank(strongSide, weakPawnSq) == RANK_7
&& (strongPawns & (weakPawnSq + pawn_push(weakSide)))
&& (opposite_colors(bishopSq, weakPawnSq) || !more_than_one(strongPawns)))
if ( relative_rank(strongSide, weakPawn) == RANK_7
&& (strongPawns & (weakPawn + pawn_push(weakSide)))
&& (opposite_colors(strongBishop, weakPawn) || !more_than_one(strongPawns)))
{
int strongKingDist = distance(weakPawnSq, strongKingSq);
int weakKingDist = distance(weakPawnSq, weakKingSq);
int strongKingDist = distance(weakPawn, strongKing);
int weakKingDist = distance(weakPawn, weakKing);
// It's a draw if the weak king is on its back two ranks, within 2
// squares of the blocking pawn and the strong king is not
@ -364,7 +366,7 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
// unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
// and positions where qsearch will immediately correct the
// problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w)
if ( relative_rank(strongSide, weakKingSq) >= RANK_7
if ( relative_rank(strongSide, weakKing) >= RANK_7
&& weakKingDist <= 2
&& weakKingDist <= strongKingDist)
return SCALE_FACTOR_DRAW;
@ -384,15 +386,16 @@ ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
assert(pos.count<ROOK>(weakSide) == 1);
assert(pos.count<PAWN>(weakSide) >= 1);
Square kingSq = pos.square<KING>(weakSide);
Square rsq = pos.square<ROOK>(weakSide);
Square strongKing = pos.square<KING>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
Square weakRook = pos.square<ROOK>(weakSide);
if ( relative_rank(weakSide, kingSq) <= RANK_2
&& relative_rank(weakSide, pos.square<KING>(strongSide)) >= RANK_4
&& relative_rank(weakSide, rsq) == RANK_3
if ( relative_rank(weakSide, weakKing) <= RANK_2
&& relative_rank(weakSide, strongKing) >= RANK_4
&& relative_rank(weakSide, weakRook) == RANK_3
&& ( pos.pieces(weakSide, PAWN)
& attacks_bb<KING>(kingSq)
& pawn_attacks_bb(strongSide, rsq)))
& attacks_bb<KING>(weakKing)
& pawn_attacks_bb(strongSide, weakRook)))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
@ -412,89 +415,89 @@ ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
assert(verify_material(pos, weakSide, RookValueMg, 0));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.square<KING>(strongSide));
Square bksq = normalize(pos, strongSide, pos.square<KING>(weakSide));
Square wrsq = normalize(pos, strongSide, pos.square<ROOK>(strongSide));
Square wpsq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
Square brsq = normalize(pos, strongSide, pos.square<ROOK>(weakSide));
Square strongKing = normalize(pos, strongSide, pos.square<KING>(strongSide));
Square strongRook = normalize(pos, strongSide, pos.square<ROOK>(strongSide));
Square strongPawn = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
Square weakKing = normalize(pos, strongSide, pos.square<KING>(weakSide));
Square weakRook = normalize(pos, strongSide, pos.square<ROOK>(weakSide));
File f = file_of(wpsq);
Rank r = rank_of(wpsq);
Square queeningSq = make_square(f, RANK_8);
File pawnFile = file_of(strongPawn);
Rank pawnRank = rank_of(strongPawn);
Square queeningSquare = make_square(pawnFile, RANK_8);
int tempo = (pos.side_to_move() == strongSide);
// If the pawn is not too far advanced and the defending king defends the
// queening square, use the third-rank defence.
if ( r <= RANK_5
&& distance(bksq, queeningSq) <= 1
&& wksq <= SQ_H5
&& (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
if ( pawnRank <= RANK_5
&& distance(weakKing, queeningSquare) <= 1
&& strongKing <= SQ_H5
&& (rank_of(weakRook) == RANK_6 || (pawnRank <= RANK_3 && rank_of(strongRook) != RANK_6)))
return SCALE_FACTOR_DRAW;
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
if ( r == RANK_6
&& distance(bksq, queeningSq) <= 1
&& rank_of(wksq) + tempo <= RANK_6
&& (rank_of(brsq) == RANK_1 || (!tempo && distance<File>(brsq, wpsq) >= 3)))
if ( pawnRank == RANK_6
&& distance(weakKing, queeningSquare) <= 1
&& rank_of(strongKing) + tempo <= RANK_6
&& (rank_of(weakRook) == RANK_1 || (!tempo && distance<File>(weakRook, strongPawn) >= 3)))
return SCALE_FACTOR_DRAW;
if ( r >= RANK_6
&& bksq == queeningSq
&& rank_of(brsq) == RANK_1
&& (!tempo || distance(wksq, wpsq) >= 2))
if ( pawnRank >= RANK_6
&& weakKing == queeningSquare
&& rank_of(weakRook) == RANK_1
&& (!tempo || distance(strongKing, strongPawn) >= 2))
return SCALE_FACTOR_DRAW;
// 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.
if ( wpsq == SQ_A7
&& wrsq == SQ_A8
&& (bksq == SQ_H7 || bksq == SQ_G7)
&& file_of(brsq) == FILE_A
&& (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
if ( strongPawn == SQ_A7
&& strongRook == SQ_A8
&& (weakKing == SQ_H7 || weakKing == SQ_G7)
&& file_of(weakRook) == FILE_A
&& (rank_of(weakRook) <= RANK_3 || file_of(strongKing) >= FILE_D || rank_of(strongKing) <= RANK_5))
return SCALE_FACTOR_DRAW;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
if ( r <= RANK_5
&& bksq == wpsq + NORTH
&& distance(wksq, wpsq) - tempo >= 2
&& distance(wksq, brsq) - tempo >= 2)
if ( pawnRank <= RANK_5
&& weakKing == strongPawn + NORTH
&& distance(strongKing, strongPawn) - tempo >= 2
&& distance(strongKing, weakRook) - tempo >= 2)
return SCALE_FACTOR_DRAW;
// 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,
// and the defending king cannot gain tempi by threatening the attacking rook.
if ( r == RANK_7
&& f != FILE_A
&& file_of(wrsq) == f
&& wrsq != queeningSq
&& (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
&& (distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo))
return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(wksq, queeningSq));
if ( pawnRank == RANK_7
&& pawnFile != FILE_A
&& file_of(strongRook) == pawnFile
&& strongRook != queeningSquare
&& (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo)
&& (distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo))
return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(strongKing, queeningSquare));
// Similar to the above, but with the pawn further back
if ( f != FILE_A
&& file_of(wrsq) == f
&& wrsq < wpsq
&& (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
&& (distance(wksq, wpsq + NORTH) < distance(bksq, wpsq + NORTH) - 2 + tempo)
&& ( distance(bksq, wrsq) + tempo >= 3
|| ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo
&& (distance(wksq, wpsq + NORTH) < distance(bksq, wrsq) + tempo))))
if ( pawnFile != FILE_A
&& file_of(strongRook) == pawnFile
&& strongRook < strongPawn
&& (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo)
&& (distance(strongKing, strongPawn + NORTH) < distance(weakKing, strongPawn + NORTH) - 2 + tempo)
&& ( distance(weakKing, strongRook) + tempo >= 3
|| ( distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo
&& (distance(strongKing, strongPawn + NORTH) < distance(weakKing, strongPawn) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- 8 * distance(wpsq, queeningSq)
- 2 * distance(wksq, queeningSq));
- 8 * distance(strongPawn, queeningSquare)
- 2 * distance(strongKing, queeningSquare));
// If the pawn is not far advanced and the defending king is somewhere in
// the pawn's path, it's probably a draw.
if (r <= RANK_4 && bksq > wpsq)
if (pawnRank <= RANK_4 && weakKing > strongPawn)
{
if (file_of(bksq) == file_of(wpsq))
if (file_of(weakKing) == file_of(strongPawn))
return ScaleFactor(10);
if ( distance<File>(bksq, wpsq) == 1
&& distance(wksq, bksq) > 2)
return ScaleFactor(24 - 2 * distance(wksq, bksq));
if ( distance<File>(weakKing, strongPawn) == 1
&& distance(strongKing, weakKing) > 2)
return ScaleFactor(24 - 2 * distance(strongKing, weakKing));
}
return SCALE_FACTOR_NONE;
}
@ -508,10 +511,11 @@ ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
// Test for a rook pawn
if (pos.pieces(PAWN) & (FileABB | FileHBB))
{
Square ksq = pos.square<KING>(weakSide);
Square bsq = pos.square<BISHOP>(weakSide);
Square psq = pos.square<PAWN>(strongSide);
Rank rk = relative_rank(strongSide, psq);
Square weakKing = pos.square<KING>(weakSide);
Square weakBishop = pos.square<BISHOP>(weakSide);
Square strongKing = pos.square<KING>(strongSide);
Square strongPawn = pos.square<PAWN>(strongSide);
Rank pawnRank = relative_rank(strongSide, strongPawn);
Direction push = pawn_push(strongSide);
// If the pawn is on the 5th rank and the pawn (currently) is on
@ -519,11 +523,11 @@ ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
// a fortress. Depending on the king position give a moderate
// reduction or a stronger one if the defending king is near the
// corner but not trapped there.
if (rk == RANK_5 && !opposite_colors(bsq, psq))
if (pawnRank == RANK_5 && !opposite_colors(weakBishop, strongPawn))
{
int d = distance(psq + 3 * push, ksq);
int d = distance(strongPawn + 3 * push, weakKing);
if (d <= 2 && !(d == 0 && ksq == pos.square<KING>(strongSide) + 2 * push))
if (d <= 2 && !(d == 0 && weakKing == strongKing + 2 * push))
return ScaleFactor(24);
else
return ScaleFactor(48);
@ -533,10 +537,10 @@ ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
// it's drawn if the bishop attacks the square in front of the
// pawn from a reasonable distance and the defending king is near
// the corner
if ( rk == RANK_6
&& distance(psq + 2 * push, ksq) <= 1
&& (attacks_bb<BISHOP>(bsq) & (psq + push))
&& distance<File>(bsq, psq) >= 2)
if ( pawnRank == RANK_6
&& distance(strongPawn + 2 * push, weakKing) <= 1
&& (attacks_bb<BISHOP>(weakBishop) & (strongPawn + push))
&& distance<File>(weakBishop, strongPawn) >= 2)
return ScaleFactor(8);
}
@ -551,22 +555,22 @@ ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, RookValueMg, 2));
assert(verify_material(pos, weakSide, RookValueMg, 1));
Square wpsq1 = pos.squares<PAWN>(strongSide)[0];
Square wpsq2 = pos.squares<PAWN>(strongSide)[1];
Square bksq = pos.square<KING>(weakSide);
Square strongPawn1 = pos.squares<PAWN>(strongSide)[0];
Square strongPawn2 = pos.squares<PAWN>(strongSide)[1];
Square weakKing = pos.square<KING>(weakSide);
// Does the stronger side have a passed pawn?
if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
if (pos.pawn_passed(strongSide, strongPawn1) || pos.pawn_passed(strongSide, strongPawn2))
return SCALE_FACTOR_NONE;
Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2));
Rank pawnRank = std::max(relative_rank(strongSide, strongPawn1), relative_rank(strongSide, strongPawn2));
if ( distance<File>(bksq, wpsq1) <= 1
&& distance<File>(bksq, wpsq2) <= 1
&& relative_rank(strongSide, bksq) > r)
if ( distance<File>(weakKing, strongPawn1) <= 1
&& distance<File>(weakKing, strongPawn2) <= 1
&& relative_rank(strongSide, weakKing) > pawnRank)
{
assert(r > RANK_1 && r < RANK_7);
return ScaleFactor(7 * r);
assert(pawnRank > RANK_1 && pawnRank < RANK_7);
return ScaleFactor(7 * pawnRank);
}
return SCALE_FACTOR_NONE;
}
@ -581,12 +585,12 @@ ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
assert(pos.count<PAWN>(strongSide) >= 2);
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
Square ksq = pos.square<KING>(weakSide);
Bitboard pawns = pos.pieces(strongSide, PAWN);
Square weakKing = pos.square<KING>(weakSide);
Bitboard strongPawns = pos.pieces(strongSide, PAWN);
// If all pawns are ahead of the king on a single rook file, it's a draw.
if (!((pawns & ~FileABB) || (pawns & ~FileHBB)) &&
!(pawns & ~passed_pawn_span(weakSide, ksq)))
if (!((strongPawns & ~FileABB) || (strongPawns & ~FileHBB)) &&
!(strongPawns & ~passed_pawn_span(weakSide, weakKing)))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
@ -603,19 +607,19 @@ ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
Square pawnSq = pos.square<PAWN>(strongSide);
Square strongBishopSq = pos.square<BISHOP>(strongSide);
Square weakBishopSq = pos.square<BISHOP>(weakSide);
Square weakKingSq = pos.square<KING>(weakSide);
Square strongPawn = pos.square<PAWN>(strongSide);
Square strongBishop = pos.square<BISHOP>(strongSide);
Square weakBishop = pos.square<BISHOP>(weakSide);
Square weakKing = pos.square<KING>(weakSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away
if ( (forward_file_bb(strongSide, pawnSq) & weakKingSq)
&& ( opposite_colors(weakKingSq, strongBishopSq)
|| relative_rank(strongSide, weakKingSq) <= RANK_6))
if ( (forward_file_bb(strongSide, strongPawn) & weakKing)
&& ( opposite_colors(weakKing, strongBishop)
|| relative_rank(strongSide, weakKing) <= RANK_6))
return SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
if (opposite_colors(strongBishopSq, weakBishopSq))
if (opposite_colors(strongBishop, weakBishop))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
@ -629,36 +633,36 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, BishopValueMg, 2));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
Square wbsq = pos.square<BISHOP>(strongSide);
Square bbsq = pos.square<BISHOP>(weakSide);
Square strongBishop = pos.square<BISHOP>(strongSide);
Square weakBishop = pos.square<BISHOP>(weakSide);
if (!opposite_colors(wbsq, bbsq))
if (!opposite_colors(strongBishop, weakBishop))
return SCALE_FACTOR_NONE;
Square ksq = pos.square<KING>(weakSide);
Square psq1 = pos.squares<PAWN>(strongSide)[0];
Square psq2 = pos.squares<PAWN>(strongSide)[1];
Square weakKing = pos.square<KING>(weakSide);
Square strongPawn1 = pos.squares<PAWN>(strongSide)[0];
Square strongPawn2 = pos.squares<PAWN>(strongSide)[1];
Square blockSq1, blockSq2;
if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
if (relative_rank(strongSide, strongPawn1) > relative_rank(strongSide, strongPawn2))
{
blockSq1 = psq1 + pawn_push(strongSide);
blockSq2 = make_square(file_of(psq2), rank_of(psq1));
blockSq1 = strongPawn1 + pawn_push(strongSide);
blockSq2 = make_square(file_of(strongPawn2), rank_of(strongPawn1));
}
else
{
blockSq1 = psq2 + pawn_push(strongSide);
blockSq2 = make_square(file_of(psq1), rank_of(psq2));
blockSq1 = strongPawn2 + pawn_push(strongSide);
blockSq2 = make_square(file_of(strongPawn1), rank_of(strongPawn2));
}
switch (distance<File>(psq1, psq2))
switch (distance<File>(strongPawn1, strongPawn2))
{
case 0:
// Both pawns are on the same file. It's an easy draw if the defender firmly
// controls some square in the frontmost pawn's path.
if ( file_of(ksq) == file_of(blockSq1)
&& relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1)
&& opposite_colors(ksq, wbsq))
if ( file_of(weakKing) == file_of(blockSq1)
&& relative_rank(strongSide, weakKing) >= relative_rank(strongSide, blockSq1)
&& opposite_colors(weakKing, strongBishop))
return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
@ -667,16 +671,16 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
// Pawns on adjacent files. It's a draw if the 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
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq2
if ( weakKing == blockSq1
&& opposite_colors(weakKing, strongBishop)
&& ( weakBishop == blockSq2
|| (attacks_bb<BISHOP>(blockSq2, pos.pieces()) & pos.pieces(weakSide, BISHOP))
|| distance<Rank>(psq1, psq2) >= 2))
|| distance<Rank>(strongPawn1, strongPawn2) >= 2))
return SCALE_FACTOR_DRAW;
else if ( ksq == blockSq2
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq1
else if ( weakKing == blockSq2
&& opposite_colors(weakKing, strongBishop)
&& ( weakBishop == blockSq1
|| (attacks_bb<BISHOP>(blockSq1, pos.pieces()) & pos.pieces(weakSide, BISHOP))))
return SCALE_FACTOR_DRAW;
else
@ -698,14 +702,14 @@ ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
Square pawnSq = pos.square<PAWN>(strongSide);
Square strongBishopSq = pos.square<BISHOP>(strongSide);
Square weakKingSq = pos.square<KING>(weakSide);
Square strongPawn = pos.square<PAWN>(strongSide);
Square strongBishop = pos.square<BISHOP>(strongSide);
Square weakKing = pos.square<KING>(weakSide);
if ( file_of(weakKingSq) == file_of(pawnSq)
&& relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
&& ( opposite_colors(weakKingSq, strongBishopSq)
|| relative_rank(strongSide, weakKingSq) <= RANK_6))
if ( file_of(weakKing) == file_of(strongPawn)
&& relative_rank(strongSide, strongPawn) < relative_rank(strongSide, weakKing)
&& ( opposite_colors(weakKing, strongBishop)
|| relative_rank(strongSide, weakKing) <= RANK_6))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
@ -724,18 +728,18 @@ ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
// Assume strongSide is white and the pawn is on files A-D
Square wksq = normalize(pos, strongSide, pos.square<KING>(strongSide));
Square bksq = normalize(pos, strongSide, pos.square<KING>(weakSide));
Square psq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
Square strongKing = normalize(pos, strongSide, pos.square<KING>(strongSide));
Square weakKing = normalize(pos, strongSide, pos.square<KING>(weakSide));
Square strongPawn = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
// If the pawn has advanced to the fifth rank or further, and is not a
// rook pawn, it's too dangerous to assume that it's at least a draw.
if (rank_of(psq) >= RANK_5 && file_of(psq) != FILE_A)
if (rank_of(strongPawn) >= RANK_5 && file_of(strongPawn) != FILE_A)
return SCALE_FACTOR_NONE;
// 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.
return Bitbases::probe(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
return Bitbases::probe(strongKing, strongPawn, weakKing, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}