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BadFish/src/evaluate.cpp
Marco Costalba 935fc09fd4 Two small fixes in passed pawns evaluation 
The one in evaluate_passed_pawns() is just a micro
optimization, the other in evaluate_unstoppable_pawns()
is indeed a fix, although almost unmeasurable in real
games.

Bugs report and fixes by Marek Kwiatkowski

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
2010-07-26 06:10:01 +01:00

1122 lines
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/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2010 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
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
////
//// Includes
////
#include <cassert>
#include <cstring>
#include "bitcount.h"
#include "evaluate.h"
#include "material.h"
#include "pawns.h"
#include "thread.h"
#include "ucioption.h"
////
//// Local definitions
////
namespace {
const int Sign[2] = { 1, -1 };
// Evaluation grain size, must be a power of 2
const int GrainSize = 8;
// Evaluation weights, initialized from UCI options
enum { Mobility, PawnStructure, PassedPawns, Space, KingDangerUs, KingDangerThem };
Score Weights[6];
typedef Value V;
#define S(mg, eg) make_score(mg, eg)
// Internal evaluation weights. These are applied on top of the evaluation
// weights read from UCI parameters. The purpose is to be able to change
// the evaluation weights while keeping the default values of the UCI
// parameters at 100, which looks prettier.
//
// Values modified by Joona Kiiski
const Score WeightsInternal[] = {
S(248, 271), S(233, 201), S(252, 259), S(46, 0), S(247, 0), S(259, 0)
};
// Knight mobility bonus in middle game and endgame, indexed by the number
// of attacked squares not occupied by friendly piecess.
const Score KnightMobilityBonus[16] = {
S(-38,-33), S(-25,-23), S(-12,-13), S( 0,-3),
S( 12, 7), S( 25, 17), S( 31, 22), S(38, 27), S(38, 27)
};
// Bishop mobility bonus in middle game and endgame, indexed by the number
// of attacked squares not occupied by friendly pieces. X-ray attacks through
// queens are also included.
const Score BishopMobilityBonus[16] = {
S(-25,-30), S(-11,-16), S( 3, -2), S(17, 12),
S( 31, 26), S( 45, 40), S(57, 52), S(65, 60),
S( 71, 65), S( 74, 69), S(76, 71), S(78, 73),
S( 79, 74), S( 80, 75), S(81, 76), S(81, 76)
};
// Rook mobility bonus in middle game and endgame, indexed by the number
// of attacked squares not occupied by friendly pieces. X-ray attacks through
// queens and rooks are also included.
const Score RookMobilityBonus[16] = {
S(-20,-36), S(-14,-19), S(-8, -3), S(-2, 13),
S( 4, 29), S( 10, 46), S(14, 62), S(19, 79),
S( 23, 95), S( 26,106), S(27,111), S(28,114),
S( 29,116), S( 30,117), S(31,118), S(32,118)
};
// Queen mobility bonus in middle game and endgame, indexed by the number
// of attacked squares not occupied by friendly pieces.
const Score QueenMobilityBonus[32] = {
S(-10,-18), S(-8,-13), S(-6, -7), S(-3, -2), S(-1, 3), S( 1, 8),
S( 3, 13), S( 5, 19), S( 8, 23), S(10, 27), S(12, 32), S(15, 34),
S( 16, 35), S(17, 35), S(18, 35), S(20, 35), S(20, 35), S(20, 35),
S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
S( 20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35), S(20, 35),
S( 20, 35), S(20, 35)
};
// Pointers table to access mobility tables through piece type
const Score* MobilityBonus[8] = { 0, 0, KnightMobilityBonus, BishopMobilityBonus,
RookMobilityBonus, QueenMobilityBonus, 0, 0 };
// Outpost bonuses for knights and bishops, indexed by square (from white's
// point of view).
const Value KnightOutpostBonus[64] = {
// A B C D E F G H
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
V(0), V(0), V(4), V(8), V(8), V(4), V(0), V(0), // 3
V(0), V(4),V(17),V(26),V(26),V(17), V(4), V(0), // 4
V(0), V(8),V(26),V(35),V(35),V(26), V(8), V(0), // 5
V(0), V(4),V(17),V(17),V(17),V(17), V(4), V(0), // 6
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
};
const Value BishopOutpostBonus[64] = {
// A B C D E F G H
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 1
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 2
V(0), V(0), V(5), V(5), V(5), V(5), V(0), V(0), // 3
V(0), V(5),V(10),V(10),V(10),V(10), V(5), V(0), // 4
V(0),V(10),V(21),V(21),V(21),V(21),V(10), V(0), // 5
V(0), V(5), V(8), V(8), V(8), V(8), V(5), V(0), // 6
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // 7
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0) // 8
};
// ThreatBonus[attacking][attacked] contains bonus according to which
// piece type attacks which one.
const Score ThreatBonus[8][8] = {
{}, {},
{ S(0, 0), S( 7, 39), S( 0, 0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
{ S(0, 0), S( 7, 39), S(24, 49), S( 0, 0), S(41,100), S(41,100) }, // BISHOP
{ S(0, 0), S(-1, 29), S(15, 49), S(15, 49), S( 0, 0), S(24, 49) }, // ROOK
{ S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0, 0) } // QUEEN
};
// ThreatedByPawnPenalty[] contains a penalty according to which piece
// type is attacked by an enemy pawn.
const Score ThreatedByPawnPenalty[8] = {
S(0, 0), S(0, 0), S(56, 70), S(56, 70), S(76, 99), S(86, 118)
};
#undef S
// Bonus for unstoppable passed pawns
const Value UnstoppablePawnValue = Value(0x500);
// Rooks and queens on the 7th rank (modified by Joona Kiiski)
const Score RookOn7thBonus = make_score(47, 98);
const Score QueenOn7thBonus = make_score(27, 54);
// Rooks on open files (modified by Joona Kiiski)
const Score RookOpenFileBonus = make_score(43, 43);
const Score RookHalfOpenFileBonus = make_score(19, 19);
// Penalty for rooks trapped inside a friendly king which has lost the
// right to castle.
const Value TrappedRookPenalty = Value(180);
// Penalty for a bishop on a7/h7 (a2/h2 for black) which is trapped by
// enemy pawns.
const Score TrappedBishopA7H7Penalty = make_score(300, 300);
// Bitboard masks for detecting trapped bishops on a7/h7 (a2/h2 for black)
const Bitboard MaskA7H7[2] = {
((1ULL << SQ_A7) | (1ULL << SQ_H7)),
((1ULL << SQ_A2) | (1ULL << SQ_H2))
};
// Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
// a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
// happen in Chess960 games.
const Score TrappedBishopA1H1Penalty = make_score(100, 100);
// Bitboard masks for detecting trapped bishops on a1/h1 (a8/h8 for black)
const Bitboard MaskA1H1[2] = {
((1ULL << SQ_A1) | (1ULL << SQ_H1)),
((1ULL << SQ_A8) | (1ULL << SQ_H8))
};
// The SpaceMask[color] contains the area of the board which is considered
// by the space evaluation. In the middle game, each side is given a bonus
// based on how many squares inside this area are safe and available for
// friendly minor pieces.
const Bitboard SpaceMask[2] = {
(1ULL<<SQ_C2) | (1ULL<<SQ_D2) | (1ULL<<SQ_E2) | (1ULL<<SQ_F2) |
(1ULL<<SQ_C3) | (1ULL<<SQ_D3) | (1ULL<<SQ_E3) | (1ULL<<SQ_F3) |
(1ULL<<SQ_C4) | (1ULL<<SQ_D4) | (1ULL<<SQ_E4) | (1ULL<<SQ_F4),
(1ULL<<SQ_C7) | (1ULL<<SQ_D7) | (1ULL<<SQ_E7) | (1ULL<<SQ_F7) |
(1ULL<<SQ_C6) | (1ULL<<SQ_D6) | (1ULL<<SQ_E6) | (1ULL<<SQ_F6) |
(1ULL<<SQ_C5) | (1ULL<<SQ_D5) | (1ULL<<SQ_E5) | (1ULL<<SQ_F5)
};
/// King danger constants and variables. The king danger scores are taken
/// from the KingDangerTable[]. Various little "meta-bonuses" measuring
/// the strength of the enemy attack are added up into an integer, which
/// is used as an index to KingDangerTable[].
// KingAttackWeights[] contains king attack weights by piece type
const int KingAttackWeights[8] = { 0, 0, 2, 2, 3, 5 };
// Bonuses for enemy's safe checks
const int QueenContactCheckBonus = 3;
const int QueenCheckBonus = 2;
const int RookCheckBonus = 1;
const int BishopCheckBonus = 1;
const int KnightCheckBonus = 1;
// InitKingDanger[] contains bonuses based on the position of the defending
// king.
const int InitKingDanger[64] = {
2, 0, 2, 5, 5, 2, 0, 2,
2, 2, 4, 8, 8, 4, 2, 2,
7, 10, 12, 12, 12, 12, 10, 7,
15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15,
15, 15, 15, 15, 15, 15, 15, 15
};
// KingDangerTable[color][] contains the actual king danger weighted scores
Score KingDangerTable[2][128];
// Pawn and material hash tables, indexed by the current thread id.
// Note that they will be initialized at 0 being global variables.
MaterialInfoTable* MaterialTable[MAX_THREADS];
PawnInfoTable* PawnTable[MAX_THREADS];
// Sizes of pawn and material hash tables
const int PawnTableSize = 16384;
const int MaterialTableSize = 1024;
// Function prototypes
template<bool HasPopCnt>
Value do_evaluate(const Position& pos, EvalInfo& ei);
template<Color Us, bool HasPopCnt>
void init_attack_tables(const Position& pos, EvalInfo& ei);
template<Color Us, bool HasPopCnt>
void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei);
template<Color Us, bool HasPopCnt>
void evaluate_king(const Position& pos, EvalInfo& ei);
template<Color Us>
void evaluate_threats(const Position& pos, EvalInfo& ei);
template<Color Us, bool HasPopCnt>
int evaluate_space(const Position& pos, EvalInfo& ei);
template<Color Us>
void evaluate_passed_pawns(const Position& pos, EvalInfo& ei);
void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei);
void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo& ei);
void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei);
inline Score apply_weight(Score v, Score weight);
Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]);
Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight);
void init_safety();
}
////
//// Functions
////
/// evaluate() is the main evaluation function. It always computes two
/// values, an endgame score and a middle game score, and interpolates
/// between them based on the remaining material.
Value evaluate(const Position& pos, EvalInfo& ei) {
return CpuHasPOPCNT ? do_evaluate<true>(pos, ei)
: do_evaluate<false>(pos, ei);
}
namespace {
template<bool HasPopCnt>
Value do_evaluate(const Position& pos, EvalInfo& ei) {
ScaleFactor factor[2];
assert(pos.is_ok());
assert(pos.thread() >= 0 && pos.thread() < MAX_THREADS);
assert(!pos.is_check());
memset(&ei, 0, sizeof(EvalInfo));
// Initialize by reading the incrementally updated scores included in the
// position object (material + piece square tables)
ei.value = pos.value();
// Probe the material hash table
ei.mi = MaterialTable[pos.thread()]->get_material_info(pos);
ei.value += ei.mi->material_value();
// If we have a specialized evaluation function for the current material
// configuration, call it and return
if (ei.mi->specialized_eval_exists())
return ei.mi->evaluate(pos);
// After get_material_info() call that modifies them
factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
// Probe the pawn hash table
ei.pi = PawnTable[pos.thread()]->get_pawn_info(pos);
ei.value += apply_weight(ei.pi->pawns_value(), Weights[PawnStructure]);
// Initialize attack bitboards with pawns evaluation
init_attack_tables<WHITE, HasPopCnt>(pos, ei);
init_attack_tables<BLACK, HasPopCnt>(pos, ei);
// Evaluate pieces
evaluate_pieces_of_color<WHITE, HasPopCnt>(pos, ei);
evaluate_pieces_of_color<BLACK, HasPopCnt>(pos, ei);
// Kings. Kings are evaluated after all other pieces for both sides,
// because we need complete attack information for all pieces when computing
// the king safety evaluation.
evaluate_king<WHITE, HasPopCnt>(pos, ei);
evaluate_king<BLACK, HasPopCnt>(pos, ei);
// Evaluate tactical threats, we need full attack info including king
evaluate_threats<WHITE>(pos, ei);
evaluate_threats<BLACK>(pos, ei);
// Evaluate passed pawns, we need full attack info including king
evaluate_passed_pawns<WHITE>(pos, ei);
evaluate_passed_pawns<BLACK>(pos, ei);
// If one side has only a king, check whether exsists any unstoppable passed pawn
if (!pos.non_pawn_material(WHITE) || !pos.non_pawn_material(BLACK))
evaluate_unstoppable_pawns(pos, ei);
Phase phase = ei.mi->game_phase();
// Middle-game specific evaluation terms
if (phase > PHASE_ENDGAME)
{
// Pawn storms in positions with opposite castling
if ( square_file(pos.king_square(WHITE)) >= FILE_E
&& square_file(pos.king_square(BLACK)) <= FILE_D)
ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
else if ( square_file(pos.king_square(WHITE)) <= FILE_D
&& square_file(pos.king_square(BLACK)) >= FILE_E)
ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
// Evaluate space for both sides
if (ei.mi->space_weight() > 0)
{
int s = evaluate_space<WHITE, HasPopCnt>(pos, ei) - evaluate_space<BLACK, HasPopCnt>(pos, ei);
ei.value += apply_weight(make_score(s * ei.mi->space_weight(), 0), Weights[Space]);
}
}
// Mobility
ei.value += apply_weight(ei.mobility, Weights[Mobility]);
// If we don't already have an unusual scale factor, check for opposite
// colored bishop endgames, and use a lower scale for those
if ( phase < PHASE_MIDGAME
&& pos.opposite_colored_bishops()
&& ( (factor[WHITE] == SCALE_FACTOR_NORMAL && eg_value(ei.value) > Value(0))
|| (factor[BLACK] == SCALE_FACTOR_NORMAL && eg_value(ei.value) < Value(0))))
{
ScaleFactor sf;
// Only the two bishops ?
if ( pos.non_pawn_material(WHITE) == BishopValueMidgame
&& pos.non_pawn_material(BLACK) == BishopValueMidgame)
{
// Check for KBP vs KB with only a single pawn that is almost
// certainly a draw or at least two pawns.
bool one_pawn = (pos.piece_count(WHITE, PAWN) + pos.piece_count(BLACK, PAWN) == 1);
sf = one_pawn ? ScaleFactor(8) : ScaleFactor(32);
}
else
// Endgame with opposite-colored bishops, but also other pieces. Still
// a bit drawish, but not as drawish as with only the two bishops.
sf = ScaleFactor(50);
if (factor[WHITE] == SCALE_FACTOR_NORMAL)
factor[WHITE] = sf;
if (factor[BLACK] == SCALE_FACTOR_NORMAL)
factor[BLACK] = sf;
}
// Interpolate between the middle game and the endgame score
return Sign[pos.side_to_move()] * scale_by_game_phase(ei.value, phase, factor);
}
} // namespace
/// init_eval() initializes various tables used by the evaluation function
void init_eval(int threads) {
assert(threads <= MAX_THREADS);
for (int i = 0; i < MAX_THREADS; i++)
{
if (i >= threads)
{
delete PawnTable[i];
delete MaterialTable[i];
PawnTable[i] = NULL;
MaterialTable[i] = NULL;
continue;
}
if (!PawnTable[i])
PawnTable[i] = new PawnInfoTable(PawnTableSize);
if (!MaterialTable[i])
MaterialTable[i] = new MaterialInfoTable(MaterialTableSize);
}
}
/// quit_eval() releases heap-allocated memory at program termination
void quit_eval() {
for (int i = 0; i < MAX_THREADS; i++)
{
delete PawnTable[i];
delete MaterialTable[i];
PawnTable[i] = NULL;
MaterialTable[i] = NULL;
}
}
/// read_weights() reads evaluation weights from the corresponding UCI parameters
void read_weights(Color us) {
// King safety is asymmetrical. Our king danger level is weighted by
// "Cowardice" UCI parameter, instead the opponent one by "Aggressiveness".
const int kingDangerUs = (us == WHITE ? KingDangerUs : KingDangerThem);
const int kingDangerThem = (us == WHITE ? KingDangerThem : KingDangerUs);
Weights[Mobility] = weight_option("Mobility (Middle Game)", "Mobility (Endgame)", WeightsInternal[Mobility]);
Weights[PawnStructure] = weight_option("Pawn Structure (Middle Game)", "Pawn Structure (Endgame)", WeightsInternal[PawnStructure]);
Weights[PassedPawns] = weight_option("Passed Pawns (Middle Game)", "Passed Pawns (Endgame)", WeightsInternal[PassedPawns]);
Weights[Space] = weight_option("Space", "Space", WeightsInternal[Space]);
Weights[kingDangerUs] = weight_option("Cowardice", "Cowardice", WeightsInternal[KingDangerUs]);
Weights[kingDangerThem] = weight_option("Aggressiveness", "Aggressiveness", WeightsInternal[KingDangerThem]);
// If running in analysis mode, make sure we use symmetrical king safety. We do this
// by replacing both Weights[kingDangerUs] and Weights[kingDangerThem] by their average.
if (get_option_value_bool("UCI_AnalyseMode"))
Weights[kingDangerUs] = Weights[kingDangerThem] = (Weights[kingDangerUs] + Weights[kingDangerThem]) / 2;
init_safety();
}
namespace {
// init_attack_tables() initializes king bitboards for both sides adding
// pawn attacks. To be done before other evaluations.
template<Color Us, bool HasPopCnt>
void init_attack_tables(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
ei.kingZone[Us] = (b | (Us == WHITE ? b >> 8 : b << 8));
ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
b &= ei.attackedBy[Us][PAWN];
if (b)
ei.kingAttackersCount[Us] = count_1s_max_15<HasPopCnt>(b) / 2;
}
// evaluate_outposts() evaluates bishop and knight outposts squares
template<PieceType Piece, Color Us>
void evaluate_outposts(const Position& pos, EvalInfo& ei, Square s) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
// Initial bonus based on square
Value bonus = (Piece == BISHOP ? BishopOutpostBonus[relative_square(Us, s)]
: KnightOutpostBonus[relative_square(Us, s)]);
// Increase bonus if supported by pawn, especially if the opponent has
// no minor piece which can exchange the outpost piece
if (bonus && bit_is_set(ei.attackedBy[Us][PAWN], s))
{
if ( pos.pieces(KNIGHT, Them) == EmptyBoardBB
&& (SquaresByColorBB[square_color(s)] & pos.pieces(BISHOP, Them)) == EmptyBoardBB)
bonus += bonus + bonus / 2;
else
bonus += bonus / 2;
}
ei.value += Sign[Us] * make_score(bonus, bonus);
}
// evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given color
template<PieceType Piece, Color Us, bool HasPopCnt>
void evaluate_pieces(const Position& pos, EvalInfo& ei, Bitboard no_mob_area) {
Bitboard b;
Square s, ksq;
int mob;
File f;
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square* ptr = pos.piece_list_begin(Us, Piece);
while ((s = *ptr++) != SQ_NONE)
{
// Find attacked squares, including x-ray attacks for bishops and rooks
if (Piece == KNIGHT || Piece == QUEEN)
b = pos.attacks_from<Piece>(s);
else if (Piece == BISHOP)
b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
else if (Piece == ROOK)
b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
else
assert(false);
// Update attack info
ei.attackedBy[Us][Piece] |= b;
// King attacks
if (b & ei.kingZone[Us])
{
ei.kingAttackersCount[Us]++;
ei.kingAttackersWeight[Us] += KingAttackWeights[Piece];
Bitboard bb = (b & ei.attackedBy[Them][KING]);
if (bb)
ei.kingAdjacentZoneAttacksCount[Us] += count_1s_max_15<HasPopCnt>(bb);
}
// Mobility
mob = (Piece != QUEEN ? count_1s_max_15<HasPopCnt>(b & no_mob_area)
: count_1s<HasPopCnt>(b & no_mob_area));
ei.mobility += Sign[Us] * MobilityBonus[Piece][mob];
// Decrease score if we are attacked by an enemy pawn. Remaining part
// of threat evaluation must be done later when we have full attack info.
if (bit_is_set(ei.attackedBy[Them][PAWN], s))
ei.value -= Sign[Us] * ThreatedByPawnPenalty[Piece];
// Bishop and knight outposts squares
if ((Piece == BISHOP || Piece == KNIGHT) && pos.square_is_weak(s, Us))
evaluate_outposts<Piece, Us>(pos, ei, s);
// Special patterns: trapped bishops on a7/h7/a2/h2
// and trapped bishops on a1/h1/a8/h8 in Chess960.
if (Piece == BISHOP)
{
if (bit_is_set(MaskA7H7[Us], s))
evaluate_trapped_bishop_a7h7(pos, s, Us, ei);
if (Chess960 && bit_is_set(MaskA1H1[Us], s))
evaluate_trapped_bishop_a1h1(pos, s, Us, ei);
}
// Queen or rook on 7th rank
if ( (Piece == ROOK || Piece == QUEEN)
&& relative_rank(Us, s) == RANK_7
&& relative_rank(Us, pos.king_square(Them)) == RANK_8)
{
ei.value += Sign[Us] * (Piece == ROOK ? RookOn7thBonus : QueenOn7thBonus);
}
// Special extra evaluation for rooks
if (Piece == ROOK)
{
// Open and half-open files
f = square_file(s);
if (ei.pi->file_is_half_open(Us, f))
{
if (ei.pi->file_is_half_open(Them, f))
ei.value += Sign[Us] * RookOpenFileBonus;
else
ei.value += Sign[Us] * RookHalfOpenFileBonus;
}
// Penalize rooks which are trapped inside a king. Penalize more if
// king has lost right to castle.
if (mob > 6 || ei.pi->file_is_half_open(Us, f))
continue;
ksq = pos.king_square(Us);
if ( square_file(ksq) >= FILE_E
&& square_file(s) > square_file(ksq)
&& (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
{
// Is there a half-open file between the king and the edge of the board?
if (!ei.pi->has_open_file_to_right(Us, square_file(ksq)))
ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
: (TrappedRookPenalty - mob * 16), 0);
}
else if ( square_file(ksq) <= FILE_D
&& square_file(s) < square_file(ksq)
&& (relative_rank(Us, ksq) == RANK_1 || square_rank(ksq) == square_rank(s)))
{
// Is there a half-open file between the king and the edge of the board?
if (!ei.pi->has_open_file_to_left(Us, square_file(ksq)))
ei.value -= Sign[Us] * make_score(pos.can_castle(Us) ? (TrappedRookPenalty - mob * 16) / 2
: (TrappedRookPenalty - mob * 16), 0);
}
}
}
}
// evaluate_threats<>() assigns bonuses according to the type of attacking piece
// and the type of attacked one.
template<Color Us>
void evaluate_threats(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b;
Score bonus = make_score(0, 0);
// Enemy pieces not defended by a pawn and under our attack
Bitboard weakEnemies = pos.pieces_of_color(Them)
& ~ei.attackedBy[Them][PAWN]
& ei.attackedBy[Us][0];
if (!weakEnemies)
return;
// Add bonus according to type of attacked enemy pieces and to the
// type of attacking piece, from knights to queens. Kings are not
// considered because are already special handled in king evaluation.
for (PieceType pt1 = KNIGHT; pt1 < KING; pt1++)
{
b = ei.attackedBy[Us][pt1] & weakEnemies;
if (b)
for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
if (b & pos.pieces(pt2))
bonus += ThreatBonus[pt1][pt2];
}
ei.value += Sign[Us] * bonus;
}
// evaluate_pieces_of_color<>() assigns bonuses and penalties to all the
// pieces of a given color.
template<Color Us, bool HasPopCnt>
void evaluate_pieces_of_color(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
// Do not include in mobility squares protected by enemy pawns or occupied by our pieces
const Bitboard no_mob_area = ~(ei.attackedBy[Them][PAWN] | pos.pieces_of_color(Us));
evaluate_pieces<KNIGHT, Us, HasPopCnt>(pos, ei, no_mob_area);
evaluate_pieces<BISHOP, Us, HasPopCnt>(pos, ei, no_mob_area);
evaluate_pieces<ROOK, Us, HasPopCnt>(pos, ei, no_mob_area);
evaluate_pieces<QUEEN, Us, HasPopCnt>(pos, ei, no_mob_area);
// Sum up all attacked squares
ei.attackedBy[Us][0] = ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
| ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
| ei.attackedBy[Us][QUEEN] | ei.attackedBy[Us][KING];
}
// evaluate_king<>() assigns bonuses and penalties to a king of a given color
template<Color Us, bool HasPopCnt>
void evaluate_king(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard undefended, b, b1, b2, safe;
bool sente;
int attackUnits, shelter = 0;
const Square ksq = pos.king_square(Us);
// King shelter
if (relative_rank(Us, ksq) <= RANK_4)
{
shelter = ei.pi->get_king_shelter(pos, Us, ksq);
ei.value += Sign[Us] * make_score(shelter, 0);
}
// King safety. This is quite complicated, and is almost certainly far
// from optimally tuned.
if ( pos.piece_count(Them, QUEEN) >= 1
&& ei.kingAttackersCount[Them] >= 2
&& pos.non_pawn_material(Them) >= QueenValueMidgame + RookValueMidgame
&& ei.kingAdjacentZoneAttacksCount[Them])
{
// Is it the attackers turn to move?
sente = (Them == pos.side_to_move());
// Find the attacked squares around the king which has no defenders
// apart from the king itself
undefended = ei.attacked_by(Them) & ei.attacked_by(Us, KING);
undefended &= ~( ei.attacked_by(Us, PAWN) | ei.attacked_by(Us, KNIGHT)
| ei.attacked_by(Us, BISHOP) | ei.attacked_by(Us, ROOK)
| ei.attacked_by(Us, QUEEN));
// Initialize the 'attackUnits' variable, which is used later on as an
// index to the KingDangerTable[] array. The initial value is based on
// the number and types of the enemy's attacking pieces, the number of
// attacked and undefended squares around our king, the square of the
// king, and the quality of the pawn shelter.
attackUnits = Min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
+ 3 * (ei.kingAdjacentZoneAttacksCount[Them] + count_1s_max_15<HasPopCnt>(undefended))
+ InitKingDanger[relative_square(Us, ksq)]
- shelter / 32;
// Analyse enemy's safe queen contact checks. First find undefended
// squares around the king attacked by enemy queen...
b = undefended & ei.attacked_by(Them, QUEEN) & ~pos.pieces_of_color(Them);
if (b)
{
// ...then remove squares not supported by another enemy piece
b &= ( ei.attacked_by(Them, PAWN) | ei.attacked_by(Them, KNIGHT)
| ei.attacked_by(Them, BISHOP) | ei.attacked_by(Them, ROOK));
if (b)
attackUnits += QueenContactCheckBonus * count_1s_max_15<HasPopCnt>(b) * (sente ? 2 : 1);
}
// Analyse enemy's safe distance checks for sliders and knights
safe = ~(pos.pieces_of_color(Them) | ei.attacked_by(Us));
b1 = pos.attacks_from<ROOK>(ksq) & safe;
b2 = pos.attacks_from<BISHOP>(ksq) & safe;
// Enemy queen safe checks
b = (b1 | b2) & ei.attacked_by(Them, QUEEN);
if (b)
attackUnits += QueenCheckBonus * count_1s_max_15<HasPopCnt>(b);
// Enemy rooks safe checks
b = b1 & ei.attacked_by(Them, ROOK);
if (b)
attackUnits += RookCheckBonus * count_1s_max_15<HasPopCnt>(b);
// Enemy bishops safe checks
b = b2 & ei.attacked_by(Them, BISHOP);
if (b)
attackUnits += BishopCheckBonus * count_1s_max_15<HasPopCnt>(b);
// Enemy knights safe checks
b = pos.attacks_from<KNIGHT>(ksq) & ei.attacked_by(Them, KNIGHT) & safe;
if (b)
attackUnits += KnightCheckBonus * count_1s_max_15<HasPopCnt>(b);
// To index KingDangerTable[] attackUnits must be in [0, 99] range
attackUnits = Min(99, Max(0, attackUnits));
// Finally, extract the king danger score from the KingDangerTable[]
// array and subtract the score from evaluation. Set also ei.kingDanger[]
// value that will be used for pruning because this value can sometimes
// be very big, and so capturing a single attacking piece can therefore
// result in a score change far bigger than the value of the captured piece.
ei.value -= Sign[Us] * KingDangerTable[Us][attackUnits];
ei.kingDanger[Us] = mg_value(KingDangerTable[Us][attackUnits]);
}
}
// evaluate_passed_pawns<>() evaluates the passed pawns of the given color
template<Color Us>
void evaluate_passed_pawns(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard squaresToQueen, defendedSquares, unsafeSquares, supportingPawns;
Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(Us);
while (b)
{
Square s = pop_1st_bit(&b);
assert(pos.pawn_is_passed(Us, s));
int r = int(relative_rank(Us, s) - RANK_2);
int tr = r * (r - 1);
// Base bonus based on rank
Value mbonus = Value(20 * tr);
Value ebonus = Value(10 + r * r * 10);
if (tr)
{
Square blockSq = s + pawn_push(Us);
// Adjust bonus based on kings proximity
ebonus -= Value(square_distance(pos.king_square(Us), blockSq) * 3 * tr);
ebonus -= Value(square_distance(pos.king_square(Us), blockSq + pawn_push(Us)) * 1 * tr);
ebonus += Value(square_distance(pos.king_square(Them), blockSq) * 6 * tr);
// If the pawn is free to advance, increase bonus
if (pos.square_is_empty(blockSq))
{
squaresToQueen = squares_in_front_of(Us, s);
defendedSquares = squaresToQueen & ei.attacked_by(Us);
// If there is an enemy rook or queen attacking the pawn from behind,
// add all X-ray attacks by the rook or queen. Otherwise consider only
// the squares in the pawn's path attacked or occupied by the enemy.
if ( (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them))
&& (squares_behind(Us, s) & pos.pieces(ROOK, QUEEN, Them) & pos.attacks_from<ROOK>(s)))
unsafeSquares = squaresToQueen;
else
unsafeSquares = squaresToQueen & (ei.attacked_by(Them) | pos.pieces_of_color(Them));
// If there aren't enemy attacks or pieces along the path to queen give
// huge bonus. Even bigger if we protect the pawn's path.
if (!unsafeSquares)
ebonus += Value(tr * (squaresToQueen == defendedSquares ? 17 : 15));
else
// OK, there are enemy attacks or pieces (but not pawns). Are those
// squares which are attacked by the enemy also attacked by us ?
// If yes, big bonus (but smaller than when there are no enemy attacks),
// if no, somewhat smaller bonus.
ebonus += Value(tr * ((unsafeSquares & defendedSquares) == unsafeSquares ? 13 : 8));
// At last, add a small bonus when there are no *friendly* pieces
// in the pawn's path.
if (!(squaresToQueen & pos.pieces_of_color(Us)))
ebonus += Value(tr);
}
} // tr != 0
// Increase the bonus if the passed pawn is supported by a friendly pawn
// on the same rank and a bit smaller if it's on the previous rank.
supportingPawns = pos.pieces(PAWN, Us) & neighboring_files_bb(s);
if (supportingPawns & rank_bb(s))
ebonus += Value(r * 20);
else if (supportingPawns & rank_bb(s - pawn_push(Us)))
ebonus += Value(r * 12);
// Rook pawns are a special case: They are sometimes worse, and
// sometimes better than other passed pawns. It is difficult to find
// good rules for determining whether they are good or bad. For now,
// we try the following: Increase the value for rook pawns if the
// other side has no pieces apart from a knight, and decrease the
// value if the other side has a rook or queen.
if (square_file(s) == FILE_A || square_file(s) == FILE_H)
{
if (pos.non_pawn_material(Them) <= KnightValueMidgame)
ebonus += ebonus / 4;
else if (pos.pieces(ROOK, QUEEN, Them))
ebonus -= ebonus / 4;
}
// Add the scores for this pawn to the middle game and endgame eval
ei.value += Sign[Us] * apply_weight(make_score(mbonus, ebonus), Weights[PassedPawns]);
} // while
}
// evaluate_unstoppable_pawns() evaluates the unstoppable passed pawns for both sides
void evaluate_unstoppable_pawns(const Position& pos, EvalInfo& ei) {
int movesToGo[2] = {0, 0};
Square pawnToGo[2] = {SQ_NONE, SQ_NONE};
for (Color c = WHITE; c <= BLACK; c++)
{
// Skip evaluation if other side has non-pawn pieces
if (pos.non_pawn_material(opposite_color(c)))
continue;
Bitboard b = ei.pi->passed_pawns() & pos.pieces_of_color(c);
while (b)
{
Square s = pop_1st_bit(&b);
Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
int d = square_distance(s, queeningSquare)
- int(relative_rank(c, s) == RANK_2) // Double pawn push
- square_distance(pos.king_square(opposite_color(c)), queeningSquare)
+ int(c != pos.side_to_move());
// Do we protect the path to queening ?
bool pathDefended = (ei.attacked_by(c) & squares_in_front_of(c, s)) == squares_in_front_of(c, s);
if (d < 0 || pathDefended)
{
int mtg = RANK_8 - relative_rank(c, s) - int(relative_rank(c, s) == RANK_2);
int blockerCount = count_1s_max_15(squares_in_front_of(c, s) & pos.occupied_squares());
mtg += blockerCount;
d += blockerCount;
if ((d < 0 || pathDefended) && (!movesToGo[c] || movesToGo[c] > mtg))
{
movesToGo[c] = mtg;
pawnToGo[c] = s;
}
}
}
}
// Neither side has an unstoppable passed pawn?
if (!(movesToGo[WHITE] | movesToGo[BLACK]))
return;
// Does only one side have an unstoppable passed pawn?
if (!movesToGo[WHITE] || !movesToGo[BLACK])
{
Color winnerSide = movesToGo[WHITE] ? WHITE : BLACK;
ei.value += make_score(0, Sign[winnerSide] * (UnstoppablePawnValue - Value(0x40 * movesToGo[winnerSide])));
}
else
{ // Both sides have unstoppable pawns! Try to find out who queens
// first. We begin by transforming 'movesToGo' to the number of
// plies until the pawn queens for both sides.
movesToGo[WHITE] *= 2;
movesToGo[BLACK] *= 2;
movesToGo[pos.side_to_move()]--;
Color winnerSide = movesToGo[WHITE] < movesToGo[BLACK] ? WHITE : BLACK;
Color loserSide = opposite_color(winnerSide);
// If one side queens at least three plies before the other, that side wins
if (movesToGo[winnerSide] <= movesToGo[loserSide] - 3)
ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
// If one side queens one ply before the other and checks the king or attacks
// the undefended opponent's queening square, that side wins. To avoid cases
// where the opponent's king could move somewhere before first pawn queens we
// consider only free paths to queen for both pawns.
else if ( !(squares_in_front_of(WHITE, pawnToGo[WHITE]) & pos.occupied_squares())
&& !(squares_in_front_of(BLACK, pawnToGo[BLACK]) & pos.occupied_squares()))
{
assert(movesToGo[loserSide] - movesToGo[winnerSide] == 1);
Square winnerQSq = relative_square(winnerSide, make_square(square_file(pawnToGo[winnerSide]), RANK_8));
Square loserQSq = relative_square(loserSide, make_square(square_file(pawnToGo[loserSide]), RANK_8));
Bitboard b = pos.occupied_squares();
clear_bit(&b, pawnToGo[winnerSide]);
clear_bit(&b, pawnToGo[loserSide]);
b = queen_attacks_bb(winnerQSq, b);
if ( (b & pos.pieces(KING, loserSide))
||(bit_is_set(b, loserQSq) && !bit_is_set(ei.attacked_by(loserSide), loserQSq)))
ei.value += Sign[winnerSide] * make_score(0, UnstoppablePawnValue - Value(0x40 * (movesToGo[winnerSide]/2)));
}
}
}
// evaluate_trapped_bishop_a7h7() determines whether a bishop on a7/h7
// (a2/h2 for black) is trapped by enemy pawns, and assigns a penalty
// if it is.
void evaluate_trapped_bishop_a7h7(const Position& pos, Square s, Color us, EvalInfo &ei) {
assert(square_is_ok(s));
assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
Square b6 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B6 : SQ_G6);
Square b8 = relative_square(us, (square_file(s) == FILE_A) ? SQ_B8 : SQ_G8);
if ( pos.piece_on(b6) == piece_of_color_and_type(opposite_color(us), PAWN)
&& pos.see(s, b6) < 0
&& pos.see(s, b8) < 0)
{
ei.value -= Sign[us] * TrappedBishopA7H7Penalty;
}
}
// evaluate_trapped_bishop_a1h1() determines whether a bishop on a1/h1
// (a8/h8 for black) is trapped by a friendly pawn on b2/g2 (b7/g7 for
// black), and assigns a penalty if it is. This pattern can obviously
// only occur in Chess960 games.
void evaluate_trapped_bishop_a1h1(const Position& pos, Square s, Color us, EvalInfo& ei) {
Piece pawn = piece_of_color_and_type(us, PAWN);
Square b2, b3, c3;
assert(Chess960);
assert(square_is_ok(s));
assert(pos.piece_on(s) == piece_of_color_and_type(us, BISHOP));
if (square_file(s) == FILE_A)
{
b2 = relative_square(us, SQ_B2);
b3 = relative_square(us, SQ_B3);
c3 = relative_square(us, SQ_C3);
}
else
{
b2 = relative_square(us, SQ_G2);
b3 = relative_square(us, SQ_G3);
c3 = relative_square(us, SQ_F3);
}
if (pos.piece_on(b2) == pawn)
{
Score penalty;
if (!pos.square_is_empty(b3))
penalty = 2 * TrappedBishopA1H1Penalty;
else if (pos.piece_on(c3) == pawn)
penalty = TrappedBishopA1H1Penalty;
else
penalty = TrappedBishopA1H1Penalty / 2;
ei.value -= Sign[us] * penalty;
}
}
// evaluate_space() computes the space evaluation for a given side. The
// space evaluation is a simple bonus based on the number of safe squares
// available for minor pieces on the central four files on ranks 2--4. Safe
// squares one, two or three squares behind a friendly pawn are counted
// twice. Finally, the space bonus is scaled by a weight taken from the
// material hash table.
template<Color Us, bool HasPopCnt>
int evaluate_space(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
// Find the safe squares for our pieces inside the area defined by
// SpaceMask[us]. A square is unsafe if it is attacked by an enemy
// pawn, or if it is undefended and attacked by an enemy piece.
Bitboard safe = SpaceMask[Us]
& ~pos.pieces(PAWN, Us)
& ~ei.attacked_by(Them, PAWN)
& (ei.attacked_by(Us) | ~ei.attacked_by(Them));
// Find all squares which are at most three squares behind some friendly pawn
Bitboard behind = pos.pieces(PAWN, Us);
behind |= (Us == WHITE ? behind >> 8 : behind << 8);
behind |= (Us == WHITE ? behind >> 16 : behind << 16);
return count_1s_max_15<HasPopCnt>(safe) + count_1s_max_15<HasPopCnt>(behind & safe);
}
// apply_weight() applies an evaluation weight to a value trying to prevent overflow
inline Score apply_weight(Score v, Score w) {
return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, (int(eg_value(v)) * eg_value(w)) / 0x100);
}
// scale_by_game_phase() interpolates between a middle game and an endgame score,
// based on game phase. It also scales the return value by a ScaleFactor array.
Value scale_by_game_phase(const Score& v, Phase ph, const ScaleFactor sf[]) {
assert(mg_value(v) > -VALUE_INFINITE && mg_value(v) < VALUE_INFINITE);
assert(eg_value(v) > -VALUE_INFINITE && eg_value(v) < VALUE_INFINITE);
assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
Value eg = eg_value(v);
ScaleFactor f = sf[eg > Value(0) ? WHITE : BLACK];
Value ev = Value((eg * f) / SCALE_FACTOR_NORMAL);
int result = (mg_value(v) * ph + ev * (128 - ph)) / 128;
return Value(result & ~(GrainSize - 1));
}
// weight_option() computes the value of an evaluation weight, by combining
// two UCI-configurable weights (midgame and endgame) with an internal weight.
Score weight_option(const std::string& mgOpt, const std::string& egOpt, Score internalWeight) {
// Scale option value from 100 to 256
int mg = get_option_value_int(mgOpt) * 256 / 100;
int eg = get_option_value_int(egOpt) * 256 / 100;
return apply_weight(make_score(mg, eg), internalWeight);
}
// init_safety() initizes the king safety evaluation, based on UCI
// parameters. It is called from read_weights().
void init_safety() {
const Value MaxSlope = Value(30);
const Value Peak = Value(1280);
Value t[100];
// First setup the base table
for (int i = 0; i < 100; i++)
{
t[i] = Value(int(0.4 * i * i));
if (i > 0)
t[i] = Min(t[i], t[i - 1] + MaxSlope);
t[i] = Min(t[i], Peak);
}
// Then apply the weights and get the final KingDangerTable[] array
for (Color c = WHITE; c <= BLACK; c++)
for (int i = 0; i < 100; i++)
KingDangerTable[c][i] = apply_weight(make_score(t[i], 0), Weights[KingDangerUs + c]);
}
}
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