kate/BadFish
1
0
Fork 0
mirror of https://github.com/sockspls/badfish synced 2025-04-30 16:53:09 +00:00
Code Issues Releases Wiki Activity

Revert back KBPsK to latest Gary's version

Browse source 
The bug was found to be elsewhere. This version
is correct and also is able to detect as draw
positions like:

8/8/5b2/8/8/4k1p1/6P1/5K2 b - - 6 133

bench: 8678654
This commit is contained in:
Marco Costalba 2014-05-04 09:31:25 +02:00
parent c0d3010438
commit f1240483fb
1 changed files with 38 additions and 13 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

51
src/endgame.cpp
View file

@ -364,27 +364,52 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
// be detected even when the weaker side has some pawns. // be detected even when the weaker side has some pawns.
Bitboard pawns = pos.pieces(strongSide, PAWN); Bitboard pawns = pos.pieces(strongSide, PAWN);
File pawnsFile = file_of(lsb(pawns)); File pawnFile = file_of(pos.list<PAWN>(strongSide)[0]);
// All pawns are on a single rook file ? // All pawns are on a single rook file ?
if ( (pawnsFile == FILE_A || pawnsFile == FILE_H) if ( (pawnFile == FILE_A || pawnFile == FILE_H)
&& !(pawns & ~file_bb(pawnsFile))) && !(pawns & ~file_bb(pawnFile)))
{ {
Square bishopSq = pos.list<BISHOP>(strongSide)[0]; Square bishopSq = pos.list<BISHOP>(strongSide)[0];
Square queeningSq = relative_square(strongSide, make_square(pawnsFile, RANK_8)); Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8));
Square kingSq = pos.king_square(weakSide); Square kingSq = pos.king_square(weakSide);
// If the bishop has the wrong color, and the defending king is on the file
// of the pawn(s) or the neighboring file, then it's potentially a draw.
if ( opposite_colors(queeningSq, bishopSq) if ( opposite_colors(queeningSq, bishopSq)
&& file_distance(kingSq, lsb(pawns)) <= 1) && square_distance(queeningSq, kingSq) <= 1)
{ return SCALE_FACTOR_DRAW;
// If the defending king has distance <= 1 to the promotion square or }
// is placed somewhere in front of the frontmost pawn, it's a draw.
Rank rank = relative_rank(strongSide, (frontmost_sq(strongSide, pawns)));
if ( square_distance(kingSq, queeningSq) <= 1 // If all the pawns are on the same B or G file, then it's potentially a draw
|| relative_rank(strongSide, kingSq) >= rank) 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 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];
// 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)))
&& (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 1))
{
int strongKingDist = square_distance(weakPawnSq, strongKingSq);
int weakKingDist = square_distance(weakPawnSq, weakKingSq);
// 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
// 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
&& weakKingDist <= 2
&& weakKingDist <= strongKingDist)
return SCALE_FACTOR_DRAW; return SCALE_FACTOR_DRAW;
} }
} }