HCha/Stockfish
1
0
Fork 0
mirror of https://github.com/HChaZZY/Stockfish.git synced 2025-12-21 17:46:26 +08:00
Code Issues Packages Projects Releases Wiki Activity

Simplification of KPsK function

Browse Source 
Also the drawing criteria has been slightly loosened.
It now detects a draw if the king is ahead of all the
pawns and on the same file or the adjacent file.

bench: 7700683
This commit is contained in:
Chris Caino
2013-10-15 00:20:34 +01:00
committed by Marco Costalba
parent 2bf18bfc63
commit 3cddb0c076
1 changed files with 8 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/endgame.cpp
View File

@@ -684,25 +684,15 @@ ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
Square ksq = pos.king_square(weakSide); Square ksq = pos.king_square(weakSide);
Bitboard pawns = pos.pieces(strongSide, PAWN); Bitboard pawns = pos.pieces(strongSide, PAWN);
Square psq = pos.list<PAWN>(strongSide)[0];
// Are all pawns on the 'a' file? // If all pawns are ahead of the king, all pawns are on a single
if (!(pawns & ~FileABB)) // rook file and the king is within one file of the pawns then draw.
{ if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq)))
// Does the defending king block the pawns? && !((pawns & ~FileABB) && (pawns & ~FileHBB))
if ( square_distance(ksq, relative_square(strongSide, SQ_A8)) <= 1 && file_distance(ksq, psq) <= 1)
|| ( file_of(ksq) == FILE_A
&& !(in_front_bb(strongSide, rank_of(ksq)) & pawns)))
return SCALE_FACTOR_DRAW; return SCALE_FACTOR_DRAW;
}
// Are all pawns on the 'h' file?
else if (!(pawns & ~FileHBB))
{
// Does the defending king block the pawns?
if ( square_distance(ksq, relative_square(strongSide, SQ_H8)) <= 1
|| ( file_of(ksq) == FILE_H
&& !(in_front_bb(strongSide, rank_of(ksq)) & pawns)))
return SCALE_FACTOR_DRAW;
}
return SCALE_FACTOR_NONE; return SCALE_FACTOR_NONE;
} }