Tweak the pawn attack span for backward pawns and the zone behind
opponent opposing pawns. This is important in positional play and
one of weaknesses of the engine in recent high level games.
STC
LLR: -2.95 (-2.94,2.94) [0.50,4.50]
Total: 66843 W: 14884 L: 14717 D: 37242
http://tests.stockfishchess.org/tests/view/
5d8dcb1b0ebc590f3beb2956
LTC
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 77699 W: 12993 L: 12602 D: 52104
http://tests.stockfishchess.org/tests/view/
5d8de9bc0ebc590f3beb3d00
See discussion in https://github.com/official-stockfish/Stockfish/pull/2332
Bench:
4012371
constexpr Score KnightOnQueen = S( 16, 12);
constexpr Score LongDiagonalBishop = S( 45, 0);
constexpr Score MinorBehindPawn = S( 18, 3);
constexpr Score KnightOnQueen = S( 16, 12);
constexpr Score LongDiagonalBishop = S( 45, 0);
constexpr Score MinorBehindPawn = S( 18, 3);
- constexpr Score Outpost = S( 18, 6);
+ constexpr Score Outpost = S( 16, 5);
constexpr Score PassedFile = S( 11, 8);
constexpr Score PawnlessFlank = S( 17, 95);
constexpr Score RestrictedPiece = S( 7, 7);
constexpr Score PassedFile = S( 11, 8);
constexpr Score PawnlessFlank = S( 17, 95);
constexpr Score RestrictedPiece = S( 7, 7);
constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
- Bitboard neighbours, stoppers, support, phalanx;
+ Bitboard neighbours, stoppers, support, phalanx, opposed;
Bitboard lever, leverPush;
Square s;
Bitboard lever, leverPush;
Square s;
- bool opposed, backward, passed, doubled;
+ bool backward, passed, doubled;
Score score = SCORE_ZERO;
const Square* pl = pos.squares<PAWN>(Us);
Score score = SCORE_ZERO;
const Square* pl = pos.squares<PAWN>(Us);
Rank r = relative_rank(Us, s);
Rank r = relative_rank(Us, s);
- e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
-
// Flag the pawn
opposed = theirPawns & forward_file_bb(Us, s);
stoppers = theirPawns & passed_pawn_span(Us, s);
// Flag the pawn
opposed = theirPawns & forward_file_bb(Us, s);
stoppers = theirPawns & passed_pawn_span(Us, s);
backward = !(neighbours & forward_ranks_bb(Them, s))
&& (stoppers & (leverPush | (s + Up)));
backward = !(neighbours & forward_ranks_bb(Them, s))
&& (stoppers & (leverPush | (s + Up)));
+ // Span of backward pawns and span behind opposing pawns are not included
+ // in the pawnAttacksSpan bitboard.
+ if (!backward || phalanx)
+ {
+ if (opposed)
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s) &
+ ~pawn_attack_span(Us, frontmost_sq(Them, opposed));
+ else
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+ }
+
// A pawn is passed if one of the three following conditions is true:
// (a) there is no stoppers except some levers
// (b) the only stoppers are the leverPush, but we outnumber them
// A pawn is passed if one of the three following conditions is true:
// (a) there is no stoppers except some levers
// (b) the only stoppers are the leverPush, but we outnumber them
// Score this pawn
if (support | phalanx)
{
// Score this pawn
if (support | phalanx)
{
- int v = Connected[r] * (2 + bool(phalanx) - opposed)
+ int v = Connected[r] * (2 + bool(phalanx) - bool(opposed))
+ 21 * popcount(support);
score += make_score(v, v * (r - 2) / 4);
}
else if (!neighbours)
+ 21 * popcount(support);
score += make_score(v, v * (r - 2) / 4);
}
else if (!neighbours)
- score -= Isolated + WeakUnopposed * !opposed;
+ score -= Isolated
+ + WeakUnopposed * !opposed;
- score -= Backward + WeakUnopposed * !opposed;
+ score -= Backward
+ + WeakUnopposed * !opposed;
if (!support)
score -= Doubled * doubled
if (!support)
score -= Doubled * doubled