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Merge KBPP vs KB endgame from iPhone Glaurung

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Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2009-03-22 13:06:29 +01:00
parent 16abc165d8
commit cc8e915ed5
3 changed files with 79 additions and 0 deletions
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src/endgame.cpp
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@@ -57,6 +57,7 @@ ScalingFunction<KRPKR> ScaleKRPKR(WHITE), ScaleKRKRP(BLACK); // KRP vs KR
ScalingFunction<KRPPKRP> ScaleKRPPKRP(WHITE), ScaleKRPKRPP(BLACK); // KRPP vs KRP
ScalingFunction<KPsK> ScaleKPsK(WHITE), ScaleKKPs(BLACK); // King and pawns vs king
ScalingFunction<KBPKB> ScaleKBPKB(WHITE), ScaleKBKBP(BLACK); // KBP vs KB
ScalingFunction<KBPPKB> ScaleKBPPKB(WHITE), ScaleKBKBPP(BLACK); // KBPP vs KB
ScalingFunction<KBPKN> ScaleKBPKN(WHITE), ScaleKNKBP(BLACK); // KBP vs KN
ScalingFunction<KNPK> ScaleKNPK(WHITE), ScaleKKNP(BLACK); // KNP vs K
ScalingFunction<KPKP> ScaleKPKPw(WHITE), ScaleKPKPb(BLACK); // KPKP
@@ -732,6 +733,80 @@ ScaleFactor ScalingFunction<KBPKB>::apply(const Position &pos) {
}
/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic
/// draws with opposite-colored bishops.
template<>
ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) {
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 (square_color(wbsq) == square_color(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)
&& square_color(ksq) != square_color(wbsq))
return ScaleFactor(0);
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
&& square_color(ksq) != square_color(wbsq)
&& ( bbsq == blockSq2
|| (pos.piece_attacks<BISHOP>(blockSq2) & pos.bishops(weakerSide))
|| rank_distance(r1, r2) >= 2))
return ScaleFactor(0);
else if ( ksq == blockSq2
&& square_color(ksq) != square_color(wbsq)
&& ( bbsq == blockSq1
|| (pos.piece_attacks<BISHOP>(blockSq1) & pos.bishops(weakerSide))))
return ScaleFactor(0);
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,