/*
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) 2008-2015 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
#include "bitcount.h"
#include "pawns.h"
#include "position.h"
+#include "thread.h"
namespace {
#define V Value
#define S(mg, eg) make_score(mg, eg)
- // Doubled pawn penalty by opposed flag and file
- const Score Doubled[2][FILE_NB] = {
- { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
- S(23, 48), S(23, 48), S(20, 48), S(13, 43) },
- { S(13, 43), S(20, 48), S(23, 48), S(23, 48),
- S(23, 48), S(23, 48), S(20, 48), S(13, 43) }};
-
// Isolated pawn penalty by opposed flag and file
const Score Isolated[2][FILE_NB] = {
- { S(37, 45), S(54, 52), S(60, 52), S(60, 52),
- S(60, 52), S(60, 52), S(54, 52), S(37, 45) },
- { S(25, 30), S(36, 35), S(40, 35), S(40, 35),
- S(40, 35), S(40, 35), S(36, 35), S(25, 30) }};
-
- // Backward pawn penalty by opposed flag and file
- const Score Backward[2][FILE_NB] = {
- { S(30, 42), S(43, 46), S(49, 46), S(49, 46),
- S(49, 46), S(49, 46), S(43, 46), S(30, 42) },
- { 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
- const Score ChainMember[FILE_NB] = {
- S(11,-1), S(13,-1), S(13,-1), S(14,-1),
- S(14,-1), S(13,-1), S(13,-1), S(11,-1)
- };
-
- // Candidate passed pawn bonus by rank
- const Score CandidatePassed[RANK_NB] = {
- S( 0, 0), S( 6, 13), S(6,13), S(14,29),
- S(34,68), S(83,166), S(0, 0), S( 0, 0)
- };
-
- // 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) };
-
- // Danger of enemy pawns moving toward our king indexed by
- // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
- const Value StormDanger[3][RANK_NB] = {
- { V( 0), V(64), V(128), V(51), V(26) },
- { V(26), V(32), V( 96), V(38), V(20) },
- { V( 0), V( 0), V( 64), V(25), V(13) }};
+ { S(31, 36), S(45, 41), S(50, 41), S(50, 41),
+ S(50, 41), S(50, 41), S(45, 41), S(31, 36) },
+ { S(21, 24), S(30, 28), S(33, 28), S(33, 28),
+ S(33, 28), S(33, 28), S(30, 28), S(21, 24) } };
+
+ // Backward pawn penalty by opposed flag
+ const Score Backward[2] = { S(56, 33), S(41, 19) };
+
+ // 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(17, 8), S(21, 12) };
+
+ // Connected pawn bonus by opposed, phalanx, twice supported and rank
+ Score Connected[2][2][2][RANK_NB];
+
+ // Doubled pawn penalty by file
+ const Score Doubled[FILE_NB] = {
+ S(11, 34), S(17, 38), S(19, 38), S(19, 38),
+ S(19, 38), S(19, 38), S(17, 38), S(11, 34) };
+
+ // Lever bonus by rank
+ const Score Lever[RANK_NB] = {
+ S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
+ S(17, 16), S(33, 32), S(0, 0), S(0, 0) };
+
+ // Weakness of our pawn shelter in front of the king by [distance from edge][rank]
+ const Value ShelterWeakness[][RANK_NB] = {
+ { V( 97), V(21), V(26), V(51), V(87), V( 89), V( 99) },
+ { V(120), V( 0), V(28), V(76), V(88), V(103), V(104) },
+ { V(101), V( 7), V(54), V(78), V(77), V( 92), V(101) },
+ { V( 80), V(11), V(44), V(68), V(87), V( 90), V(119) } };
+
+ // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]
+ const Value StormDanger[][4][RANK_NB] = {
+ { { V( 0), V( 67), V( 134), V(38), V(32) },
+ { V( 0), V( 57), V( 139), V(37), V(22) },
+ { V( 0), V( 43), V( 115), V(43), V(27) },
+ { V( 0), V( 68), V( 124), V(57), V(32) } },
+ { { V(20), V( 43), V( 100), V(56), V(20) },
+ { V(23), V( 20), V( 98), V(40), V(15) },
+ { V(23), V( 39), V( 103), V(36), V(18) },
+ { V(28), V( 19), V( 108), V(42), V(26) } },
+ { { V( 0), V( 0), V( 75), V(14), V( 2) },
+ { V( 0), V( 0), V( 150), V(30), V( 4) },
+ { V( 0), V( 0), V( 160), V(22), V( 5) },
+ { V( 0), V( 0), V( 166), V(24), V(13) } },
+ { { V( 0), V(-283), V(-281), V(57), V(31) },
+ { V( 0), V( 58), V( 141), V(39), V(18) },
+ { V( 0), V( 65), V( 142), V(48), V(32) },
+ { V( 0), V( 60), V( 126), V(51), V(19) } } };
// Max bonus for king safety. Corresponds to start position with all the pawns
- // in front of the king and no enemy pawn on the horizont.
- const Value MaxSafetyBonus = V(263);
+ // in front of the king and no enemy pawn on the horizon.
+ const Value MaxSafetyBonus = V(258);
#undef S
#undef V
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b;
+ Bitboard b, neighbours, doubled, supported, phalanx;
Square s;
- File f;
- Rank r;
- bool passed, isolated, doubled, opposed, chain, backward, candidate;
- Score value = SCORE_ZERO;
- const Square* pl = pos.list<PAWN>(Us);
+ bool passed, isolated, opposed, backward, lever, connected;
+ Score score = SCORE_ZERO;
+ const Square* pl = pos.squares<PAWN>(Us);
+ const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
- Bitboard ourPawns = pos.pieces(Us, PAWN);
+ Bitboard ourPawns = pos.pieces(Us , PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = 0;
+ e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
e->kingSquares[Us] = SQ_NONE;
e->semiopenFiles[Us] = 0xFF;
e->pawnAttacks[Us] = shift_bb<Right>(ourPawns) | shift_bb<Left>(ourPawns);
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- f = file_of(s);
- r = rank_of(s);
+ File f = file_of(s);
- // This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
-
- // Our rank plus previous one. Used for chain detection
- b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
-
- // 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));
-
- // Test for backward pawn
- backward = false;
-
- // 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
- // or if can capture an enemy pawn it cannot be backward either.
- if ( !(passed | isolated | chain)
- && !(ourPawns & pawn_attack_span(Them, s))
- && !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+
+ // Flag the pawn
+ neighbours = ourPawns & adjacent_files_bb(f);
+ doubled = ourPawns & forward_bb(Us, s);
+ opposed = theirPawns & forward_bb(Us, s);
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
+ lever = theirPawns & pawnAttacksBB[s];
+ phalanx = neighbours & rank_bb(s);
+ supported = neighbours & rank_bb(s - Up);
+ connected = supported | phalanx;
+ isolated = !neighbours;
+
+ // Test for backward pawn.
+ // If the pawn is passed, isolated, lever or connected it cannot be
+ // backward. If there are friendly pawns behind on adjacent files
+ // or if it is sufficiently advanced, it cannot be backward either.
+ if ( (passed | isolated | lever | connected)
+ || (ourPawns & pawn_attack_span(Them, s))
+ || (relative_rank(Us, s) >= RANK_5))
+ backward = false;
+ else
{
- // We now know that there are no friendly pawns beside or behind this
+ // We now know there are no friendly pawns beside or behind this
// pawn on adjacent files. We now check whether the pawn is
// backward by looking in the forward direction on the adjacent
- // files, and seeing whether we meet a friendly or an enemy pawn first.
- b = pos.attacks_from<PAWN>(s, Us);
-
- // Note that we are sure to find something because pawn is not passed
- // nor isolated, so loop is potentially infinite, but it isn't.
- while (!(b & (ourPawns | theirPawns)))
- b = shift_bb<Up>(b);
+ // files, and picking the closest pawn there.
+ b = pawn_attack_span(Us, s) & (ourPawns | theirPawns);
+ b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b));
- // The friendly pawn needs to be at least two ranks closer than the
- // enemy pawn in order to help the potentially backward pawn advance.
+ // If we have an enemy pawn in the same or next rank, the pawn is
+ // backward because it cannot advance without being captured.
backward = (b | shift_bb<Up>(b)) & theirPawns;
}
assert(opposed | passed | (pawn_attack_span(Us, s) & theirPawns));
- // A not passed pawn is a candidate to become passed if it is free to
- // advance and if the number of friendly pawns beside or behind this
- // pawn on adjacent files is higher or equal than the number of
- // enemy pawns in the forward direction on the adjacent files.
- candidate = !(opposed | passed | backward | isolated)
- && (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0
- && popcount<Max15>(b) >= popcount<Max15>(pawn_attack_span(Us, s) & theirPawns);
-
// Passed pawns will be properly scored in evaluation because we need
- // full attack info to evaluate passed pawns. Only the frontmost passed
+ // full attack info to evaluate them. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
if (passed && !doubled)
e->passedPawns[Us] |= s;
// Score this pawn
if (isolated)
- value -= Isolated[opposed][f];
+ score -= Isolated[opposed][f];
- if (doubled)
- value -= Doubled[opposed][f];
+ else if (backward)
+ score -= Backward[opposed];
- if (backward)
- value -= Backward[opposed][f];
+ else if (!supported)
+ score -= Unsupported[more_than_one(neighbours & rank_bb(s + Up))];
- if (chain)
- value += ChainMember[f];
+ if (connected)
+ score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
- if (candidate)
- value += CandidatePassed[relative_rank(Us, s)];
+ if (doubled)
+ score -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
+
+ if (lever)
+ score += Lever[relative_rank(Us, s)];
}
- return value;
+ b = e->semiopenFiles[Us] ^ 0xFF;
+ e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
+
+ return score;
}
} // namespace
namespace Pawns {
-/// probe() takes a position object as input, computes a Entry object, and returns
-/// a pointer to it. The result is also stored in a hash table, so we don't have
-/// to recompute everything when the same pawn structure occurs again.
+/// Pawns::init() initializes some tables needed by evaluation. Instead of using
+/// hard-coded tables, when makes sense, we prefer to calculate them with a formula
+/// to reduce independent parameters and to allow easier tuning and better insight.
+
+void init()
+{
+ static const int Seed[RANK_NB] = { 0, 8, 19, 13, 71, 94, 169, 324 };
+
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ for (int phalanx = 0; phalanx <= 1; ++phalanx)
+ for (int apex = 0; apex <= 1; ++apex)
+ for (Rank r = RANK_2; r < RANK_8; ++r)
+ {
+ int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+ v += (apex ? v / 2 : 0);
+ Connected[opposed][phalanx][apex][r] = make_score(v, v * 5 / 8);
+ }
+}
+
+
+/// Pawns::probe() looks up the current position's pawns configuration in
+/// the pawns hash table. It returns a pointer to the Entry if the position
+/// is found. Otherwise a new Entry is computed and stored there, so we don't
+/// have to recompute all when the same pawns configuration occurs again.
-Entry* probe(const Position& pos, Table& entries) {
+Entry* probe(const Position& pos) {
Key key = pos.pawn_key();
- Entry* e = entries[key];
+ Entry* e = pos.this_thread()->pawnsTable[key];
if (e->key == key)
return e;
e->key = key;
- e->value = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+ e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
+ e->asymmetry = popcount<Max15>(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
return e;
}
const Color Them = (Us == WHITE ? BLACK : WHITE);
- Value safety = MaxSafetyBonus;
+ enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing };
+
Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Rank rkUs, rkThem;
- File kf = file_of(ksq);
-
- kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf;
+ Value safety = MaxSafetyBonus;
+ File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
- for (int f = kf - 1; f <= kf + 1; f++)
+ for (File f = center - File(1); f <= center + File(1); ++f)
{
- b = ourPawns & FileBB[f];
- rkUs = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(b)) : RANK_1;
- safety -= ShelterWeakness[rkUs];
-
- b = theirPawns & FileBB[f];
- rkThem = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(b)) : RANK_1;
- safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem];
+ b = ourPawns & file_bb(f);
+ Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+
+ b = theirPawns & file_bb(f);
+ Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
+
+ safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+ + StormDanger
+ [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing :
+ rkUs == RANK_1 ? NoFriendlyPawn :
+ rkThem == rkUs + 1 ? BlockedByPawn : Unblocked]
+ [std::min(f, FILE_H - f)][rkThem];
}
return safety;
}
-/// Entry::update_safety() calculates and caches a bonus for king safety. It is
-/// called only when king square changes, about 20% of total king_safety() calls.
+/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
+/// when king square changes, which is about 20% of total king_safety() calls.
template<Color Us>
-Score Entry::update_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
- castleRights[Us] = pos.can_castle(Us);
- minKPdistance[Us] = 0;
+ castlingRights[Us] = pos.can_castle(Us);
+ int minKingPawnDistance = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
+ while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
+ return make_score(0, -16 * minKingPawnDistance);
Value bonus = shelter_storm<Us>(pos, ksq);
- // If we can castle use the bonus after the castle if is bigger
- if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
+ // If we can castle use the bonus after the castling if it is bigger
+ 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_castle_right(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]);
+ return make_score(bonus, -16 * minKingPawnDistance);
}
// Explicit template instantiation
-template Score Entry::update_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::update_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
} // namespace Pawns
projects / stockfish / blobdiff