X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=c3f7872f9e7bb38ec40bc3d9134e7a57de7e11eb;hp=e2b26344986ad51d129aafbf9fba91ba8d2857fc;hb=7f623206f413b96170d432b401fe3c647325d01a;hpb=3b46df546dd8b17963abae887acff6e91e2b945e
diff --git a/src/pawns.cpp b/src/pawns.cpp
index e2b26344..c3f7872f 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -2,7 +2,7 @@
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) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2015-2020 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
@@ -18,6 +18,7 @@
along with this program. If not, see .
*/
+#include
#include
#include "bitboard.h"
@@ -31,12 +32,15 @@ namespace {
#define S(mg, eg) make_score(mg, eg)
// Pawn penalties
- constexpr Score Backward = S( 9, 24);
- constexpr Score Doubled = S(11, 56);
- constexpr Score Isolated = S( 5, 15);
+ constexpr Score Backward = S( 9, 24);
+ constexpr Score BlockedStorm = S(82, 82);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+ constexpr Score WeakLever = S( 0, 56);
+ constexpr Score WeakUnopposed = S(13, 27);
// Connected pawn bonus
- constexpr int Connected[RANK_NB] = { 0, 13, 17, 24, 59, 96, 171 };
+ constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
// Strength of pawn shelter for our king by [distance from edge][rank].
// RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
@@ -49,12 +53,13 @@ namespace {
// Danger of enemy pawns moving toward our king by [distance from edge][rank].
// RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn
- // is behind our king.
+ // is behind our king. Note that UnblockedStorm[0][1-2] accommodate opponent pawn
+ // on edge, likely blocked by our king.
constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
- { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) },
- { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) },
- { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) },
- { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) }
+ { V( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) },
+ { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) },
+ { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) },
+ { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) }
};
#undef S
@@ -64,79 +69,86 @@ namespace {
Score evaluate(const Position& pos, Pawns::Entry* e) {
constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
+ constexpr Direction Up = pawn_push(Us);
- Bitboard b, neighbours, stoppers, doubled, support, phalanx;
- Bitboard lever, leverPush;
+ Bitboard neighbours, stoppers, support, phalanx, opposed;
+ Bitboard lever, leverPush, blocked;
Square s;
- bool opposed, backward;
+ bool backward, passed, doubled;
Score score = SCORE_ZERO;
const Square* pl = pos.squares(Us);
Bitboard ourPawns = pos.pieces( Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
- e->kingSquares[Us] = SQ_NONE;
- e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns);
+ Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns);
+
+ e->passedPawns[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb(ourPawns);
// Loop through all pawns of the current color and score each pawn
while ((s = *pl++) != SQ_NONE)
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- File f = file_of(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);
+ blocked = theirPawns & (s + Up);
stoppers = theirPawns & passed_pawn_span(Us, s);
lever = theirPawns & PawnAttacks[Us][s];
leverPush = theirPawns & PawnAttacks[Us][s + Up];
doubled = ourPawns & (s - Up);
- neighbours = ourPawns & adjacent_files_bb(f);
+ neighbours = ourPawns & adjacent_files_bb(s);
phalanx = neighbours & rank_bb(s);
support = neighbours & rank_bb(s - Up);
- // A pawn is backward when it is behind all pawns of the same color
- // on the adjacent files and cannot be safely advanced.
- backward = !(ourPawns & pawn_attack_span(Them, s + Up))
- && (stoppers & (leverPush | (s + Up)));
-
- // Passed pawns will be properly scored in evaluation because we need
- // full attack info to evaluate them. Include also not passed pawns
- // which could become passed after one or two pawn pushes when are
- // not attacked more times than defended.
- if ( !(stoppers ^ lever ^ leverPush)
- && (support || !more_than_one(lever))
- && popcount(phalanx) >= popcount(leverPush))
+ // A pawn is backward when it is behind all pawns of the same color on
+ // the adjacent files and cannot safely advance.
+ backward = !(neighbours & forward_ranks_bb(Them, s + Up))
+ && (leverPush | blocked);
+
+ // Compute additional span if pawn is not backward nor blocked
+ if (!backward && !blocked)
+ 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
+ // (c) there is only one front stopper which can be levered.
+ passed = !(stoppers ^ lever)
+ || ( !(stoppers ^ leverPush)
+ && popcount(phalanx) >= popcount(leverPush))
+ || ( stoppers == blocked && r >= RANK_5
+ && (shift(support) & ~(theirPawns | doubleAttackThem)));
+
+ // Passed pawns will be properly scored later in evaluation when we have
+ // full attack info.
+ if (passed)
e->passedPawns[Us] |= s;
- else if (stoppers == square_bb(s + Up) && r >= RANK_5)
- {
- b = shift(support) & ~theirPawns;
- while (b)
- if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
- e->passedPawns[Us] |= s;
- }
-
// Score this pawn
if (support | phalanx)
{
- int v = (phalanx ? 3 : 2) * Connected[r];
- v = 17 * popcount(support) + (v >> (opposed + 1));
+ int v = Connected[r] * (2 + bool(phalanx) - bool(opposed))
+ + 21 * popcount(support);
+
score += make_score(v, v * (r - 2) / 4);
}
+
else if (!neighbours)
- score -= Isolated, e->weakUnopposed[Us] += !opposed;
+ score -= Isolated
+ + WeakUnopposed * !opposed;
else if (backward)
- score -= Backward, e->weakUnopposed[Us] += !opposed;
+ score -= Backward
+ + WeakUnopposed * !opposed;
- if (doubled && !support)
- score -= Doubled;
+ if (!support)
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
}
return score;
@@ -171,35 +183,35 @@ Entry* probe(const Position& pos) {
/// penalty for a king, looking at the king file and the two closest files.
template
-Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
- constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
+ constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Value safety = (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
- Value(374) : Value(5);
+ Score bonus = make_score(5, 5);
File center = clamp(file_of(ksq), FILE_B, FILE_G);
for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- Rank ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+ int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
b = theirPawns & file_bb(f);
- Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+ int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
+
+ File d = map_to_queenside(f);
+ bonus += make_score(ShelterStrength[d][ourRank], 0);
- int d = std::min(f, ~f);
- safety += ShelterStrength[d][ourRank];
- safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3)
- : UnblockedStorm[d][theirRank];
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus -= BlockedStorm * int(theirRank == RANK_3);
+ else
+ bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
- return safety;
+ return bonus;
}
@@ -212,22 +224,28 @@ Score Entry::do_king_safety(const Position& pos) {
Square ksq = pos.square(Us);
kingSquares[Us] = ksq;
castlingRights[Us] = pos.castling_rights(Us);
- int minKingPawnDistance = 0;
+ auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); };
- Bitboard pawns = pos.pieces(Us, PAWN);
- if (pawns)
- while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
+ Score shelter = evaluate_shelter(pos, ksq);
- Value bonus = evaluate_shelter(pos, ksq);
+ // If we can castle use the bonus after castling if it is bigger
- // If we can castle use the bonus after the castling if it is bigger
- if (pos.can_castle(Us | KING_SIDE))
- bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_G1)));
+ if (pos.can_castle(Us & KING_SIDE))
+ shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare);
+
+ if (pos.can_castle(Us & QUEEN_SIDE))
+ shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_C1)), compare);
+
+ // In endgame we like to bring our king near our closest pawn
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ int minPawnDist = pawns ? 8 : 0;
- if (pos.can_castle(Us | QUEEN_SIDE))
- bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_C1)));
+ if (pawns & PseudoAttacks[KING][ksq])
+ minPawnDist = 1;
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- return make_score(bonus, -16 * minKingPawnDistance);
+ return shelter - make_score(0, 16 * minPawnDist);
}
// Explicit template instantiation