/*
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
{ S(20, 28), S(29, 31), S(33, 31), S(33, 31),
S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
- // Pawn chain membership bonus by file and rank (initialized by formula)
- Score ChainMember[FILE_NB][RANK_NB];
+ // Connected pawn bonus by file and rank (initialized by formula)
+ Score Connected[FILE_NB][RANK_NB];
// Candidate passed pawn bonus by rank
const Score CandidatePassed[RANK_NB] = {
S(34,68), S(83,166), S(0, 0), S( 0, 0) };
// Bonus for file distance of the two outermost pawns
- const Score PawnsFileSpan = S(0, 10);
+ const Score PawnsFileSpan = S(0, 15);
// Weakness of our pawn shelter in front of the king indexed by [rank]
const Value ShelterWeakness[RANK_NB] =
Bitboard b;
Square s;
File f;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
+ bool passed, isolated, doubled, opposed, connected, backward, candidate;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
// This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
- // Our rank plus previous one. Used for chain detection
+ // Our rank plus previous one
b = rank_bb(s) | rank_bb(s - pawn_push(Us));
- // Flag the pawn as passed, isolated, doubled or member of a pawn
- // chain (but not the backward one).
- chain = 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 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));
// Test for backward pawn.
- // If the pawn is passed, isolated, or member of a pawn chain it cannot
- // be backward. If there are friendly pawns behind on adjacent files
+ // If the pawn is passed, isolated, or connected it cannot be
+ // backward. If there are friendly pawns behind on adjacent files
// or if it can capture an enemy pawn it cannot be backward either.
- if ( (passed | isolated | chain)
+ if ( (passed | isolated | connected)
|| (ourPawns & pawn_attack_span(Them, s))
|| (pos.attacks_from<PAWN>(s, Us) & theirPawns))
backward = false;
if (backward)
value -= Backward[opposed][f];
- if (chain)
- value += ChainMember[f][relative_rank(Us, s)];
+ if (connected)
+ value += Connected[f][relative_rank(Us, s)];
if (candidate)
{
// to file distance between left and right outermost pawns.
if (pos.count<PAWN>(Us) > 1)
{
- b = ~e->semiopenFiles[Us] & 0xFF;
+ b = e->semiopenFiles[Us] ^ 0xFF;
value += PawnsFileSpan * int(msb(b) - lsb(b));
}
void init() {
- const int chainByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 };
+ const int bonusesByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 };
int bonus;
for (Rank r = RANK_1; r < RANK_8; ++r)
for (File f = FILE_A; f <= FILE_H; ++f)
{
- bonus = r * (r-1) * (r-2) + chainByFile[f] * (r/2 + 1);
- ChainMember[f][r] = make_score(bonus, bonus);
+ bonus = r * (r-1) * (r-2) + bonusesByFile[f] * (r/2 + 1);
+ Connected[f][r] = make_score(bonus, bonus);
}
}
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 & (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;