/*
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
// Bonus for file distance of the two outermost pawns
const Score PawnsFileSpan = S(0, 15);
+ // Unsupported pawn penalty
+ const Score UnsupportedPawnPenalty = S(20, 10);
+
// Weakness of our pawn shelter in front of the king indexed by [rank]
const Value ShelterWeakness[RANK_NB] =
{ V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b;
+ Bitboard b, p;
Square s;
File f;
- bool passed, isolated, doubled, opposed, connected, backward, candidate;
+ bool passed, isolated, doubled, opposed, connected, backward, candidate, unsupported;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
// This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
+ // Previous rank
+ p = rank_bb(s - pawn_push(Us));
+
// Our rank plus previous one
- b = rank_bb(s) | rank_bb(s - pawn_push(Us));
+ b = rank_bb(s) | p;
- // Flag the pawn as passed, isolated, doubled or
- // connected (but not the backward one).
- connected = ourPawns & adjacent_files_bb(f) & b;
- isolated = !(ourPawns & adjacent_files_bb(f));
- doubled = ourPawns & forward_bb(Us, s);
- opposed = theirPawns & forward_bb(Us, s);
- passed = !(theirPawns & passed_pawn_mask(Us, s));
+ // Flag the pawn as passed, isolated, doubled,
+ // unsupported or connected (but not the backward one).
+ connected = ourPawns & adjacent_files_bb(f) & b;
+ unsupported = !(ourPawns & adjacent_files_bb(f) & p);
+ isolated = !(ourPawns & adjacent_files_bb(f));
+ doubled = ourPawns & forward_bb(Us, s);
+ opposed = theirPawns & forward_bb(Us, s);
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn.
// If the pawn is passed, isolated, or connected it cannot be
if (isolated)
value -= Isolated[opposed][f];
+ if (unsupported && !isolated)
+ value -= UnsupportedPawnPenalty;
+
if (doubled)
value -= Doubled[f];
Value Entry::shelter_storm(const Position& pos, Square ksq) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
+ static const Bitboard MiddleEdges = (FileABB | FileHBB) & (Rank2BB | Rank3BB);
Value safety = MaxSafetyBonus;
Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
{
b = ourPawns & file_bb(f);
rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
- safety -= ShelterWeakness[rkUs];
b = theirPawns & file_bb(f);
rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
- safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
+
+ if ( (MiddleEdges & make_square(f, rkThem))
+ && file_of(ksq) == f
+ && relative_rank(Us, ksq) == rkThem - 1)
+ safety += Value(200);
+ else
+ safety -= ShelterWeakness[rkUs]
+ + StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
}
return safety;
Score Entry::update_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
- castlingFlags[Us] = pos.can_castle(Us);
+ castlingRights[Us] = pos.can_castle(Us);
minKPdistance[Us] = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
Value bonus = shelter_storm<Us>(pos, ksq);
// If we can castle use the bonus after the castling if it is bigger
- if (pos.can_castle(make_castling_flag(Us, KING_SIDE)))
+ if (pos.can_castle(MakeCastling<Us, KING_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
- if (pos.can_castle(make_castling_flag(Us, QUEEN_SIDE)))
+ if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);