/*
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) 2008-2014 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
}
#endif
- // Get the material key of a Position out of the given endgame key code
- // like "KBPKN". The trick here is to first forge an ad-hoc fen string
- // and then let a Position object to do the work for us. Note that the
- // fen string could correspond to an illegal position.
+ // Map the square as if strongSide is white and strongSide's only pawn
+ // is on the left half of the board.
+ Square normalize(const Position& pos, Color strongSide, Square sq) {
+
+ assert(pos.count<PAWN>(strongSide) == 1);
+
+ if (file_of(pos.list<PAWN>(strongSide)[0]) >= FILE_E)
+ sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
+
+ if (strongSide == BLACK)
+ sq = ~sq;
+
+ return sq;
+ }
+
+ // Get the material key of Position out of the given endgame key code
+ // like "KBPKN". The trick here is to first forge an ad-hoc FEN string
+ // and then let a Position object do the work for us.
Key key(const string& code, Color c) {
assert(code.length() > 0 && code.length() < 8);
std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
- string fen = sides[0] + char('0' + int(8 - code.length()))
- + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10";
+ string fen = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/"
+ + sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10";
return Position(fen, false, NULL).material_key();
}
add<KRKN>("KRKN");
add<KQKP>("KQKP");
add<KQKR>("KQKR");
- add<KBBKN>("KBBKN");
add<KNPK>("KNPK");
add<KNPKB>("KNPKB");
/// 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
+/// 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<>
if ( pos.count<QUEEN>(strongSide)
|| pos.count<ROOK>(strongSide)
+ ||(pos.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
|| pos.bishop_pair(strongSide))
result += VALUE_KNOWN_WIN;
Square loserKSq = pos.king_square(weakSide);
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
- // kbnk_mate_table() tries to drive toward corners A1 or H8,
- // if we have a bishop that cannot reach the above squares we
- // flip the kings so to drive enemy toward corners A8 or H1.
+ // kbnk_mate_table() tries to drive toward corners A1 or H8. If we have a
+ // bishop that cannot reach the above squares, we flip the kings in order
+ // to drive the enemy toward corners A8 or H1.
if (opposite_colors(bishopSq, SQ_A1))
{
winnerKSq = ~winnerKSq;
return strongSide == pos.side_to_move() ? result : -result;
}
-// Returns a square that will allow us to orient the board so that
-// strongSide is white and strongSide's only pawn is on the left
-// half of the board
-Square get_flip_sq(const Position& pos, Color strongSide) {
-
- assert(pos.count<PAWN>(strongSide) == 1);
-
- Square psq = pos.list<PAWN>(strongSide)[0];
-
- return (FILE_H * (file_of(psq) >= FILE_E)) | (RANK_8 * int(strongSide));
-}
-
-Square operator^(Square s, Square flip_sq) {
- assert(flip_sq == SQ_A1 || flip_sq == SQ_H1 || flip_sq == SQ_A8 || flip_sq == SQ_H8);
- return Square(int(s) ^ int(flip_sq));
-}
/// KP vs K. This endgame is evaluated with the help of a bitbase.
template<>
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
// Assume strongSide is white and the pawn is on files A-D
- Square flip_sq = get_flip_sq(pos, strongSide);
-
- Square wksq = pos.king_square(strongSide) ^ flip_sq;
- Square bksq = pos.king_square(weakSide) ^ flip_sq;
- Square psq = pos.list<PAWN>(strongSide)[0] ^ flip_sq;
+ Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+ Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+ Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
Square rsq = relative_square(strongSide, pos.list<ROOK>(strongSide)[0]);
Square psq = relative_square(strongSide, pos.list<PAWN>(weakSide)[0]);
- Square queeningSq = file_of(psq) | RANK_1;
+ Square queeningSq = make_square(file_of(psq), RANK_1);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
if (wksq < psq && file_of(wksq) == file_of(psq))
- result = RookValueEg - Value(square_distance(wksq, psq));
+ result = RookValueEg - square_distance(wksq, psq);
// If the weaker side's king is too far from the pawn and the rook,
// it's a win.
else if ( square_distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
&& square_distance(bksq, rsq) >= 3)
- result = RookValueEg - Value(square_distance(wksq, psq));
+ result = RookValueEg - square_distance(wksq, psq);
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
&& square_distance(bksq, psq) == 1
&& rank_of(wksq) >= RANK_4
&& square_distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
- result = Value(80 - square_distance(wksq, psq) * 8);
+ result = Value(80) - 8 * square_distance(wksq, psq);
else
- result = Value(200)
- - Value(square_distance(wksq, psq + DELTA_S) * 8)
- + Value(square_distance(bksq, psq + DELTA_S) * 8)
- + Value(square_distance(psq, queeningSq) * 8);
+ result = Value(200) - 8 * ( square_distance(wksq, psq + DELTA_S)
+ - square_distance(bksq, psq + DELTA_S)
+ - square_distance(psq, queeningSq));
return strongSide == pos.side_to_move() ? result : -result;
}
}
-/// KR vs KN. The attacking side has slightly better winning chances than
+/// 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 Endgame<KRKN>::operator()(const Position& pos) const {
}
-/// KQ vs KP. In general, a win for the stronger side, however, there are a few
-/// important exceptions. Pawn on 7th rank, A,C,F or H file, with king next can
-/// be a draw, so we scale down to distance between kings only.
+/// KQ vs KP. In general, this is a win for the stronger side, but there are a
+/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files
+/// with a king positioned next to it can be a draw, so in that case, we only
+/// use the distance between the kings.
template<>
Value Endgame<KQKP>::operator()(const Position& pos) const {
/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
/// king a bonus for having the kings close together, and for forcing the
-/// defending king towards the edge. If we also take care to avoid null move
-/// for the defending side in the search, this is usually sufficient to be
-/// able to win KQ vs KR.
+/// defending king towards the edge. If we also take care to avoid null move for
+/// the defending side in the search, this is usually sufficient to win KQ vs KR.
template<>
Value Endgame<KQKR>::operator()(const Position& pos) const {
}
-/// KBB vs KN. This is almost always a win. We try to push enemy king to a corner
-/// and away from his knight. For a reference of this difficult endgame see:
-/// en.wikipedia.org/wiki/Chess_endgame#Effect_of_tablebases_on_endgame_theory
-
-template<>
-Value Endgame<KBBKN>::operator()(const Position& pos) const {
-
- assert(verify_material(pos, strongSide, 2 * BishopValueMg, 0));
- assert(verify_material(pos, weakSide, KnightValueMg, 0));
-
- Square winnerKSq = pos.king_square(strongSide);
- Square loserKSq = pos.king_square(weakSide);
- Square knightSq = pos.list<KNIGHT>(weakSide)[0];
-
- Value result = VALUE_KNOWN_WIN
- + PushToCorners[loserKSq]
- + PushClose[square_distance(winnerKSq, loserKSq)]
- + PushAway[square_distance(loserKSq, knightSq)];
-
- return strongSide == pos.side_to_move() ? result : -result;
-}
-
-
/// Some cases of trivial draws
template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
-template<> Value Endgame<KmmKm>::operator()(const Position&) const { return VALUE_DRAW; }
-/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and
+/// KB and one or more pawns vs K. It checks for draws with rook pawns and
/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
/// will be used.
&& !(pawns & ~file_bb(pawnFile)))
{
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
- Square queeningSq = relative_square(strongSide, pawnFile | RANK_8);
+ Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8));
Square kingSq = pos.king_square(weakSide);
if ( opposite_colors(queeningSq, bishopSq)
return SCALE_FACTOR_DRAW;
}
- // All pawns on same B or G file? Then potential draw
+ // If all the pawns are on the same B or G file, then it's potentially a draw
if ( (pawnFile == FILE_B || pawnFile == FILE_G)
&& !(pos.pieces(PAWN) & ~file_bb(pawnFile))
&& pos.non_pawn_material(weakSide) == 0
&& pos.count<PAWN>(weakSide) >= 1)
{
- // Get weakSide pawn that is closest to home rank
+ // Get weakSide pawn that is closest to the home rank
Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN));
Square strongKingSq = pos.king_square(strongSide);
Square weakKingSq = pos.king_square(weakSide);
Square bishopSq = pos.list<BISHOP>(strongSide)[0];
- // Potential for a draw if our pawn is blocked on the 7th rank
+ // 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
&& (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
int strongKingDist = square_distance(weakPawnSq, strongKingSq);
int weakKingDist = square_distance(weakPawnSq, weakKingSq);
- // Draw if the weak king is on it's back two ranks, within 2
+ // 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
// closer. (I think this rule only fails in practically
// unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
}
-/// K and queen vs K, rook and one or more pawns. It tests for fortress draws with
-/// a rook on the third rank defended by a pawn.
+/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on
+/// the third rank defended by a pawn.
template<>
ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
}
-/// K, rook and one pawn vs K and a rook. This function knows a handful of the
-/// most important classes of drawn positions, but is far from perfect. It would
-/// probably be a good idea to add more knowledge in the future.
+/// KRP vs KR. This function knows a handful of the most important classes of
+/// drawn positions, but is far from perfect. It would probably be a good idea
+/// to add more knowledge in the future.
///
/// 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.
+/// which is mostly copied from Glaurung 1.x, and isn't very pretty.
template<>
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 flip_sq = get_flip_sq(pos, strongSide);
-
- Square wksq = pos.king_square(strongSide) ^ flip_sq;
- Square bksq = pos.king_square(weakSide) ^ flip_sq;
- Square wrsq = pos.list<ROOK>(strongSide)[0] ^ flip_sq;
- Square wpsq = pos.list<PAWN>(strongSide)[0] ^ flip_sq;
- Square brsq = pos.list<ROOK>(weakSide)[0] ^ flip_sq;
+ Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+ Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+ Square wrsq = normalize(pos, strongSide, pos.list<ROOK>(strongSide)[0]);
+ Square wpsq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+ Square brsq = normalize(pos, strongSide, pos.list<ROOK>(weakSide)[0]);
File f = file_of(wpsq);
Rank r = rank_of(wpsq);
- Square queeningSq = f | RANK_8;
+ Square queeningSq = make_square(f, RANK_8);
int tempo = (pos.side_to_move() == strongSide);
// If the pawn is not too far advanced and the defending king defends the
- 8 * square_distance(wpsq, queeningSq)
- 2 * square_distance(wksq, queeningSq));
- // If the pawn is not far advanced, and the defending king is somewhere in
+ // 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)
{
return SCALE_FACTOR_NONE;
}
-/// K, rook and two pawns vs K, rook and one pawn. There is only a single
-/// pattern: If the stronger side has no passed pawns and the defending king
-/// is actively placed, the position is drawish.
+/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed
+/// pawns and the defending king is actively placed, the position is drawish.
template<>
ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
Bitboard pawns = pos.pieces(strongSide, PAWN);
Square psq = pos.list<PAWN>(strongSide)[0];
- // If all pawns are ahead of the king, all pawns are on a single
- // rook file and the king is within one file of the pawns then draw.
+ // If all pawns are ahead of the king, on a single rook file and
+ // the king is within one file of the pawns, it's a draw.
if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq)))
&& !((pawns & ~FileABB) && (pawns & ~FileHBB))
&& file_distance(ksq, psq) <= 1)
}
-/// K, bishop and a pawn vs K and a bishop. There are two rules: 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. If the two
-/// bishops have opposite color, it's almost always a draw.
+/// KBP vs KB. There are two rules: 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. If the two bishops have opposite color,
+/// it's almost always a draw.
template<>
ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
}
-/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with
-/// opposite-colored bishops.
+/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
template<>
ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
{
blockSq1 = psq1 + pawn_push(strongSide);
- blockSq2 = file_of(psq2) | rank_of(psq1);
+ blockSq2 = make_square(file_of(psq2), rank_of(psq1));
}
else
{
blockSq1 = psq2 + pawn_push(strongSide);
- blockSq2 = file_of(psq1) | rank_of(psq2);
+ blockSq2 = make_square(file_of(psq1), rank_of(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.
+ // 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))
return SCALE_FACTOR_NONE;
case 1:
- // Pawns on adjacent 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.
+ // 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
}
-/// K, bisop and a pawn vs K and knight. 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.
+/// KBP vs KN. 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.
template<>
ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
}
-/// K, knight and a pawn vs K. 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.
+/// KNP vs K. 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.
template<>
ScaleFactor Endgame<KNPK>::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 flip_sq = get_flip_sq(pos, strongSide);
-
- Square pawnSq = pos.list<PAWN>(strongSide)[0] ^ flip_sq;
- Square weakKingSq = pos.king_square(weakSide) ^ flip_sq;
+ Square pawnSq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+ Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide));
if (pawnSq == SQ_A7 && square_distance(SQ_A8, weakKingSq) <= 1)
return SCALE_FACTOR_DRAW;
}
-/// K, knight and a pawn vs K and bishop. If knight can block bishop from taking
-/// pawn, it's a win. Otherwise, drawn.
+/// KNP vs KB. If knight can block bishop from taking pawn, it's a win.
+/// Otherwise the position is drawn.
template<>
ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
}
-/// K and a pawn vs K and a pawn. This is done by removing the weakest side's
-/// pawn and probing the KP vs K bitbase: If the weakest side has a draw without
-/// the pawn, she probably has at least a draw with 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).
+/// KP vs KP. This is done by removing the weakest side's pawn and probing the
+/// KP vs K bitbase: If the weakest side has a draw without the pawn, it probably
+/// has at least a draw with 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 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 flip_sq = get_flip_sq(pos, strongSide);
-
- Square wksq = pos.king_square(strongSide) ^ flip_sq;
- Square bksq = pos.king_square(weakSide) ^ flip_sq;
- Square psq = pos.list<PAWN>(strongSide)[0] ^ flip_sq;
+ Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+ Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+ Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
projects / stockfish / blobdiff