Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, 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
// Backward pawn penalty by opposed flag
const Score Backward[2] = { S(67, 42), S(49, 24) };
- // Unsupported pawn penalty, for pawns which are neither isolated or backward
- const Score Unsupported = S(20, 10);
+ // Unsupported pawn penalty for pawns which are neither isolated or backward,
+ // by number of pawns it supports [less than 2 / exactly 2].
+ const Score Unsupported[2] = { S(20, 10), S(25, 15) };
// Connected pawn bonus by opposed, phalanx, twice supported and rank
Score Connected[2][2][2][RANK_NB];
score -= Backward[opposed];
else if (!supported)
- score -= Unsupported;
+ score -= Unsupported[more_than_one(neighbours & rank_bb(s + Up))];
if (connected)
score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];