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BadFish/src/evaluate.cpp
Joona Kiiski 61a6e46664 Fix indentations for hanging pawns code 
No functional change
2015-03-29 08:54:25 +01:00

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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) 2008-2015 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/>.
*/
#include <algorithm>
#include <cassert>
#include <cstring> // For std::memset
#include <iomanip>
#include <sstream>
#include "bitcount.h"
#include "evaluate.h"
#include "material.h"
#include "pawns.h"
namespace {
namespace Tracing {
enum Term { // First 8 entries are for PieceType
MATERIAL = 8, IMBALANCE, MOBILITY, THREAT, PASSED, SPACE, TOTAL, TERM_NB
};
Score scores[COLOR_NB][TERM_NB];
std::ostream& operator<<(std::ostream& os, Term idx);
double to_cp(Value v);
void write(int idx, Color c, Score s);
void write(int idx, Score w, Score b = SCORE_ZERO);
std::string do_trace(const Position& pos);
}
// Struct EvalInfo contains various information computed and collected
// by the evaluation functions.
struct EvalInfo {
// Pointers to material and pawn hash table entries
Material::Entry* mi;
Pawns::Entry* pi;
// attackedBy[color][piece type] is a bitboard representing all squares
// attacked by a given color and piece type, attackedBy[color][ALL_PIECES]
// contains all squares attacked by the given color.
Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
// kingRing[color] is the zone around the king which is considered
// by the king safety evaluation. This consists of the squares directly
// adjacent to the king, and the three (or two, for a king on an edge file)
// squares two ranks in front of the king. For instance, if black's king
// is on g8, kingRing[BLACK] is a bitboard containing the squares f8, h8,
// f7, g7, h7, f6, g6 and h6.
Bitboard kingRing[COLOR_NB];
// kingAttackersCount[color] is the number of pieces of the given color
// which attack a square in the kingRing of the enemy king.
int kingAttackersCount[COLOR_NB];
// kingAttackersWeight[color] is the sum of the "weight" of the pieces of the
// given color which attack a square in the kingRing of the enemy king. The
// weights of the individual piece types are given by the elements in the
// KingAttackWeights array.
int kingAttackersWeight[COLOR_NB];
// kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
// color to squares directly adjacent to the enemy king. Pieces which attack
// more than one square are counted multiple times. For instance, if there is
// a white knight on g5 and black's king is on g8, this white knight adds 2
// to kingAdjacentZoneAttacksCount[WHITE].
int kingAdjacentZoneAttacksCount[COLOR_NB];
Bitboard pinnedPieces[COLOR_NB];
};
// Evaluation weights, indexed by the corresponding evaluation term
enum { Mobility, PawnStructure, PassedPawns, Space, KingSafety };
const struct Weight { int mg, eg; } Weights[] = {
{289, 344}, {233, 201}, {221, 273}, {46, 0}, {322, 0}
};
Score operator*(Score s, const Weight& w) {
return make_score(mg_value(s) * w.mg / 256, eg_value(s) * w.eg / 256);
}
#define V(v) Value(v)
#define S(mg, eg) make_score(mg, eg)
// MobilityBonus[PieceType][attacked] contains bonuses for middle and end
// game, indexed by piece type and number of attacked squares not occupied by
// friendly pieces.
const Score MobilityBonus[][32] = {
{}, {},
{ S(-68,-49), S(-46,-33), S(-3,-12), S( 5, -4), S( 9, 11), S(15, 16), // Knights
S( 23, 27), S( 33, 28), S(37, 29) },
{ S(-49,-44), S(-23,-16), S(16, 1), S(29, 16), S(40, 25), S(51, 34), // Bishops
S( 55, 43), S( 61, 49), S(64, 51), S(68, 52), S(73, 55), S(75, 60),
S( 80, 65), S( 86, 66) },
{ S(-50,-57), S(-28,-22), S(-11, 7), S(-1, 29), S( 0, 39), S( 1, 46), // Rooks
S( 10, 66), S( 16, 79), S(22, 86), S(23,103), S(30,109), S(33,111),
S( 37,115), S( 38,119), S(48,124) },
{ S(-43,-30), S(-27,-15), S( 1, -5), S( 2, -3), S(14, 10), S(18, 24), // Queens
S( 20, 27), S( 33, 37), S(33, 38), S(34, 43), S(40, 46), S(43, 56),
S( 46, 61), S( 52, 63), S(52, 63), S(57, 65), S(60, 70), S(61, 74),
S( 67, 80), S( 76, 82), S(77, 88), S(82, 94), S(86, 95), S(90, 96),
S( 94, 99), S( 96,100), S(99,111), S(99,112) }
};
// Outpost[Bishop/Knight][Square] contains bonuses for knights and bishops
// outposts, indexed by piece type and square (from white's point of view).
const Value Outpost[][SQUARE_NB] = {
{// A B C D E F G H
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Knights
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
V(0), V(0), V(3), V(9), V(9), V(3), V(0), V(0),
V(0), V(4),V(18),V(25),V(25),V(18), V(4), V(0),
V(4), V(9),V(29),V(38),V(38),V(29), V(9), V(4),
V(2), V(9),V(19),V(15),V(15),V(19), V(9), V(2) },
{
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0), // Bishops
V(0), V(0), V(0), V(0), V(0), V(0), V(0), V(0),
V(2), V(4), V(3), V(8), V(8), V(3), V(4), V(2),
V(1), V(9), V(9),V(13),V(13), V(9), V(9), V(1),
V(2), V(8),V(21),V(24),V(24),V(21), V(8), V(2),
V(0), V(4), V(6), V(6), V(6), V(6), V(4), V(0) }
};
// Threat[defended/weak][minor/major attacking][attacked PieceType] contains
// bonuses according to which piece type attacks which one.
const Score Threat[][2][PIECE_TYPE_NB] = {
{ { S(0, 0), S( 0, 0), S(19, 37), S(24, 37), S(44, 97), S(35,106) }, // Defended Minor
{ S(0, 0), S( 0, 0), S( 9, 14), S( 9, 14), S( 7, 14), S(24, 48) } }, // Defended Major
{ { S(0, 0), S( 0,32), S(33, 41), S(31, 50), S(41,100), S(35,104) }, // Weak Minor
{ S(0, 0), S( 0,27), S(26, 57), S(26, 57), S(0 , 43), S(23, 51) } } // Weak Major
};
// ThreatenedByPawn[PieceType] contains a penalty according to which piece
// type is attacked by an enemy pawn.
const Score ThreatenedByPawn[PIECE_TYPE_NB] = {
S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
};
const Score ThreatenedByHangingPawn = S(40, 60);
// Assorted bonuses and penalties used by evaluation
const Score KingOnOne = S( 2, 58);
const Score KingOnMany = S( 6,125);
const Score RookOnPawn = S( 7, 27);
const Score RookOnOpenFile = S(43, 21);
const Score RookOnSemiOpenFile = S(19, 10);
const Score BishopPawns = S( 8, 12);
const Score MinorBehindPawn = S(16, 0);
const Score TrappedRook = S(92, 0);
const Score Unstoppable = S( 0, 20);
const Score Hanging = S(31, 26);
const Score PawnAttackThreat = S(20, 20);
const Score PawnSafePush = S( 5, 5);
// 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 TrappedBishopA1H1 = S(50, 50);
#undef S
#undef V
// SpaceMask[Color] contains the area of the board which is considered
// by the space evaluation. In the middlegame, 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[COLOR_NB] = {
(FileCBB | FileDBB | FileEBB | FileFBB) & (Rank2BB | Rank3BB | Rank4BB),
(FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
};
// King danger constants and variables. The king danger scores are looked-up
// in KingDanger[]. Various little "meta-bonuses" measuring the strength
// of the enemy attack are added up into an integer, which is used as an
// index to KingDanger[].
Score KingDanger[512];
// KingAttackWeights[PieceType] contains king attack weights by piece type
const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
// Penalties for enemy's safe checks
const int QueenContactCheck = 89;
const int RookContactCheck = 71;
const int QueenCheck = 50;
const int RookCheck = 37;
const int BishopCheck = 6;
const int KnightCheck = 14;
// init_eval_info() initializes king bitboards for given color adding
// pawn attacks. To be done at the beginning of the evaluation.
template<Color Us>
void init_eval_info(const Position& pos, EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
ei.attackedBy[Us][ALL_PIECES] = ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.king_square(Them));
// Init king safety tables only if we are going to use them
if (pos.non_pawn_material(Us) >= QueenValueMg)
{
ei.kingRing[Them] = b | shift_bb<Down>(b);
b &= ei.attackedBy[Us][PAWN];
ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
}
else
ei.kingRing[Them] = ei.kingAttackersCount[Us] = 0;
}
// evaluate_outpost() evaluates bishop and knight outpost squares
template<PieceType Pt, Color Us>
Score evaluate_outpost(const Position& pos, const EvalInfo& ei, Square s) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
assert (Pt == BISHOP || Pt == KNIGHT);
// Initial bonus based on square
Value bonus = Outpost[Pt == BISHOP][relative_square(Us, s)];
// Increase bonus if supported by pawn, especially if the opponent has
// no minor piece which can trade with the outpost piece.
if (bonus && (ei.attackedBy[Us][PAWN] & s))
{
if ( !pos.pieces(Them, KNIGHT)
&& !(squares_of_color(s) & pos.pieces(Them, BISHOP)))
bonus += bonus + bonus / 2;
else
bonus += bonus / 2;
}
return make_score(bonus * 2, bonus / 2);
}
// evaluate_pieces() assigns bonuses and penalties to the pieces of a given color
template<PieceType Pt, Color Us, bool Trace>
Score evaluate_pieces(const Position& pos, EvalInfo& ei, Score* mobility, Bitboard* mobilityArea) {
Bitboard b;
Square s;
Score score = SCORE_ZERO;
const PieceType NextPt = (Us == WHITE ? Pt : PieceType(Pt + 1));
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square* pl = pos.list<Pt>(Us);
ei.attackedBy[Us][Pt] = 0;
while ((s = *pl++) != SQ_NONE)
{
// Find attacked squares, including x-ray attacks for bishops and rooks
b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(Us, QUEEN))
: Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(Us, ROOK, QUEEN))
: pos.attacks_from<Pt>(s);
if (ei.pinnedPieces[Us] & s)
b &= LineBB[pos.king_square(Us)][s];
ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
if (b & ei.kingRing[Them])
{
ei.kingAttackersCount[Us]++;
ei.kingAttackersWeight[Us] += KingAttackWeights[Pt];
Bitboard bb = b & ei.attackedBy[Them][KING];
if (bb)
ei.kingAdjacentZoneAttacksCount[Us] += popcount<Max15>(bb);
}
if (Pt == QUEEN)
b &= ~( ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP]
| ei.attackedBy[Them][ROOK]);
int mob = popcount<Pt == QUEEN ? Full : Max15>(b & mobilityArea[Us]);
mobility[Us] += MobilityBonus[Pt][mob];
if (Pt == BISHOP || Pt == KNIGHT)
{
// Bonus for outpost square
if (!(pos.pieces(Them, PAWN) & pawn_attack_span(Us, s)))
score += evaluate_outpost<Pt, Us>(pos, ei, s);
// Bonus when behind a pawn
if ( relative_rank(Us, s) < RANK_5
&& (pos.pieces(PAWN) & (s + pawn_push(Us))))
score += MinorBehindPawn;
// Penalty for pawns on same color square of bishop
if (Pt == BISHOP)
score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
// An important Chess960 pattern: A cornered bishop blocked by a friendly
// pawn diagonally in front of it is a very serious problem, especially
// when that pawn is also blocked.
if ( Pt == BISHOP
&& pos.is_chess960()
&& (s == relative_square(Us, SQ_A1) || s == relative_square(Us, SQ_H1)))
{
Square d = pawn_push(Us) + (file_of(s) == FILE_A ? DELTA_E : DELTA_W);
if (pos.piece_on(s + d) == make_piece(Us, PAWN))
score -= !pos.empty(s + d + pawn_push(Us)) ? TrappedBishopA1H1 * 4
: pos.piece_on(s + d + d) == make_piece(Us, PAWN) ? TrappedBishopA1H1 * 2
: TrappedBishopA1H1;
}
}
if (Pt == ROOK)
{
// Bonus for aligning with enemy pawns on the same rank/file
if (relative_rank(Us, s) >= RANK_5)
{
Bitboard alignedPawns = pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s];
if (alignedPawns)
score += popcount<Max15>(alignedPawns) * RookOnPawn;
}
// Bonus when on an open or semi-open file
if (ei.pi->semiopen_file(Us, file_of(s)))
score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOnOpenFile : RookOnSemiOpenFile;
// Penalize when trapped by the king, even more if king cannot castle
if (mob <= 3 && !ei.pi->semiopen_file(Us, file_of(s)))
{
Square ksq = pos.king_square(Us);
if ( ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
&& (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
&& !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
score -= (TrappedRook - make_score(mob * 22, 0)) * (1 + !pos.can_castle(Us));
}
}
}
if (Trace)
Tracing::write(Pt, Us, score);
// Recursively call evaluate_pieces() of next piece type until KING excluded
return score - evaluate_pieces<NextPt, Them, Trace>(pos, ei, mobility, mobilityArea);
}
template<>
Score evaluate_pieces<KING, WHITE, false>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
template<>
Score evaluate_pieces<KING, WHITE, true>(const Position&, EvalInfo&, Score*, Bitboard*) { return SCORE_ZERO; }
// evaluate_king() assigns bonuses and penalties to a king of a given color
template<Color Us, bool Trace>
Score evaluate_king(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard undefended, b, b1, b2, safe;
int attackUnits;
const Square ksq = pos.king_square(Us);
// King shelter and enemy pawns storm
Score score = ei.pi->king_safety<Us>(pos, ksq);
// Main king safety evaluation
if (ei.kingAttackersCount[Them])
{
// Find the attacked squares around the king which have no defenders
// apart from the king itself
undefended = ei.attackedBy[Them][ALL_PIECES]
& ei.attackedBy[Us][KING]
& ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
| ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
| ei.attackedBy[Us][QUEEN]);
// Initialize the 'attackUnits' variable, which is used later on as an
// index into the KingDanger[] 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 and the quality of
// the pawn shelter (current 'score' value).
attackUnits = std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
+ 8 * ei.kingAdjacentZoneAttacksCount[Them]
+ 25 * popcount<Max15>(undefended)
+ 11 * (ei.pinnedPieces[Us] != 0)
- mg_value(score) / 8
- !pos.count<QUEEN>(Them) * 60;
// Analyse the enemy's safe queen contact checks. Firstly, find the
// undefended squares around the king reachable by the enemy queen...
b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
if (b)
{
// ...and then remove squares not supported by another enemy piece
b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK];
if (b)
attackUnits += QueenContactCheck * popcount<Max15>(b);
}
// Analyse the enemy's safe rook contact checks. Firstly, find the
// undefended squares around the king reachable by the enemy rooks...
b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces(Them);
// Consider only squares where the enemy's rook gives check
b &= PseudoAttacks[ROOK][ksq];
if (b)
{
// ...and then remove squares not supported by another enemy piece
b &= ( ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
| ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
if (b)
attackUnits += RookContactCheck * popcount<Max15>(b);
}
// Analyse the enemy's safe distance checks for sliders and knights
safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
b1 = pos.attacks_from<ROOK >(ksq) & safe;
b2 = pos.attacks_from<BISHOP>(ksq) & safe;
// Enemy queen safe checks
b = (b1 | b2) & ei.attackedBy[Them][QUEEN];
if (b)
attackUnits += QueenCheck * popcount<Max15>(b);
// Enemy rooks safe checks
b = b1 & ei.attackedBy[Them][ROOK];
if (b)
attackUnits += RookCheck * popcount<Max15>(b);
// Enemy bishops safe checks
b = b2 & ei.attackedBy[Them][BISHOP];
if (b)
attackUnits += BishopCheck * popcount<Max15>(b);
// Enemy knights safe checks
b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe;
if (b)
attackUnits += KnightCheck * popcount<Max15>(b);
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from evaluation.
score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
}
if (Trace)
Tracing::write(KING, Us, score);
return score;
}
// evaluate_threats() assigns bonuses according to the type of attacking piece
// and the type of attacked one.
template<Color Us, bool Trace>
Score evaluate_threats(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Bitboard TRank2BB = (Us == WHITE ? Rank2BB : Rank7BB);
const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
enum { Defended, Weak };
enum { Minor, Major };
Bitboard b, weak, defended, safe_pawns, safe_pawn_threats, unsafe_pawn_threats;
Score score = SCORE_ZERO;
// Pawn Threats
b = ei.attackedBy[Us][PAWN] & (pos.pieces(Them) ^ pos.pieces(Them, PAWN));
if (b)
{
safe_pawns = pos.pieces(Us, PAWN) & (~ei.attackedBy[Them][ALL_PIECES] | ei.attackedBy[Us][ALL_PIECES]);
safe_pawn_threats = (shift_bb<Right>(safe_pawns) | shift_bb<Left>(safe_pawns)) & (pos.pieces(Them) ^ pos.pieces(Them, PAWN));
unsafe_pawn_threats = b ^ safe_pawn_threats;
// Unsafe pawn threats
if (unsafe_pawn_threats)
score += ThreatenedByHangingPawn;
// Evaluate safe pawn threats
while (safe_pawn_threats)
score += ThreatenedByPawn[type_of(pos.piece_on(pop_lsb(&safe_pawn_threats)))];
}
// Non-pawn enemies defended by a pawn
defended = (pos.pieces(Them) ^ pos.pieces(Them, PAWN)) & ei.attackedBy[Them][PAWN];
// Add a bonus according to the kind of attacking pieces
if (defended)
{
b = defended & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
while (b)
score += Threat[Defended][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
b = defended & (ei.attackedBy[Us][ROOK]);
while (b)
score += Threat[Defended][Major][type_of(pos.piece_on(pop_lsb(&b)))];
}
// Enemies not defended by a pawn and under our attack
weak = pos.pieces(Them)
& ~ei.attackedBy[Them][PAWN]
& ei.attackedBy[Us][ALL_PIECES];
// Add a bonus according to the kind of attacking pieces
if (weak)
{
b = weak & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
while (b)
score += Threat[Weak][Minor][type_of(pos.piece_on(pop_lsb(&b)))];
b = weak & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
while (b)
score += Threat[Weak][Major][type_of(pos.piece_on(pop_lsb(&b)))];
b = weak & ~ei.attackedBy[Them][ALL_PIECES];
if (b)
score += Hanging * popcount<Max15>(b);
b = weak & ei.attackedBy[Us][KING];
if (b)
score += more_than_one(b) ? KingOnMany : KingOnOne;
}
// Add a small bonus for safe pawn pushes
b = pos.pieces(Us, PAWN) & ~TRank7BB;
b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
b &= ~pos.pieces()
& ~ei.attackedBy[Them][PAWN]
& (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
if (b)
score += popcount<Full>(b) * PawnSafePush;
// Add another bonus if the pawn push attacks an enemy piece
b = (shift_bb<Left>(b) | shift_bb<Right>(b))
& pos.pieces(Them)
& ~ei.attackedBy[Us][PAWN];
if (b)
score += popcount<Max15>(b) * PawnAttackThreat;
if (Trace)
Tracing::write(Tracing::THREAT, Us, score);
return score;
}
// evaluate_passed_pawns() evaluates the passed pawns of the given color
template<Color Us, bool Trace>
Score evaluate_passed_pawns(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b, squaresToQueen, defendedSquares, unsafeSquares;
Score score = SCORE_ZERO;
b = ei.pi->passed_pawns(Us);
while (b)
{
Square s = pop_lsb(&b);
assert(pos.pawn_passed(Us, s));
int r = relative_rank(Us, s) - RANK_2;
int rr = r * (r - 1);
// Base bonus based on rank
Value mbonus = Value(17 * rr), ebonus = Value(7 * (rr + r + 1));
if (rr)
{
Square blockSq = s + pawn_push(Us);
// Adjust bonus based on the king's proximity
ebonus += distance(pos.king_square(Them), blockSq) * 5 * rr
- distance(pos.king_square(Us ), blockSq) * 2 * rr;
// If blockSq is not the queening square then consider also a second push
if (relative_rank(Us, blockSq) != RANK_8)
ebonus -= distance(pos.king_square(Us), blockSq + pawn_push(Us)) * rr;
// If the pawn is free to advance, then increase the bonus
if (pos.empty(blockSq))
{
// If there is a rook or queen attacking/defending the pawn from behind,
// consider all the squaresToQueen. Otherwise consider only the squares
// in the pawn's path attacked or occupied by the enemy.
defendedSquares = unsafeSquares = squaresToQueen = forward_bb(Us, s);
Bitboard bb = forward_bb(Them, s) & pos.pieces(ROOK, QUEEN) & pos.attacks_from<ROOK>(s);
if (!(pos.pieces(Us) & bb))
defendedSquares &= ei.attackedBy[Us][ALL_PIECES];
if (!(pos.pieces(Them) & bb))
unsafeSquares &= ei.attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
// If there aren't any enemy attacks, assign a big bonus. Otherwise
// assign a smaller bonus if the block square isn't attacked.
int k = !unsafeSquares ? 15 : !(unsafeSquares & blockSq) ? 9 : 0;
// If the path to queen is fully defended, assign a big bonus.
// Otherwise assign a smaller bonus if the block square is defended.
if (defendedSquares == squaresToQueen)
k += 6;
else if (defendedSquares & blockSq)
k += 4;
mbonus += k * rr, ebonus += k * rr;
}
else if (pos.pieces(Us) & blockSq)
mbonus += rr * 3 + r * 2 + 3, ebonus += rr + r * 2;
} // rr != 0
if (pos.count<PAWN>(Us) < pos.count<PAWN>(Them))
ebonus += ebonus / 4;
score += make_score(mbonus, ebonus);
}
if (Trace)
Tracing::write(Tracing::PASSED, Us, score * Weights[PassedPawns]);
// Add the scores to the middlegame and endgame eval
return score * Weights[PassedPawns];
}
// 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 multiplied by a weight. The aim is to
// improve play on game opening.
template<Color Us>
Score evaluate_space(const Position& pos, const EvalInfo& ei) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
// Find the safe squares for our pieces inside the area defined by
// SpaceMask[]. 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(Us, PAWN)
& ~ei.attackedBy[Them][PAWN]
& (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
// Find all squares which are at most three squares behind some friendly pawn
Bitboard behind = pos.pieces(Us, PAWN);
behind |= (Us == WHITE ? behind >> 8 : behind << 8);
behind |= (Us == WHITE ? behind >> 16 : behind << 16);
// Since SpaceMask[Us] is fully on our half of the board
assert(unsigned(safe >> (Us == WHITE ? 32 : 0)) == 0);
// Count safe + (behind & safe) with a single popcount
int bonus = popcount<Full>((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
+ pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
return make_score(bonus * weight * weight, 0);
}
// do_evaluate() is the evaluation entry point, called directly from evaluate()
template<bool Trace>
Value do_evaluate(const Position& pos) {
assert(!pos.checkers());
EvalInfo ei;
Score score, mobility[2] = { SCORE_ZERO, SCORE_ZERO };
// Initialize score by reading the incrementally updated scores included
// in the position object (material + piece square tables).
// Score is computed from the point of view of white.
score = pos.psq_score();
// Probe the material hash table
ei.mi = Material::probe(pos);
score += ei.mi->imbalance();
// 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);
// Probe the pawn hash table
ei.pi = Pawns::probe(pos);
score += ei.pi->pawns_score() * Weights[PawnStructure];
// Initialize attack and king safety bitboards
init_eval_info<WHITE>(pos, ei);
init_eval_info<BLACK>(pos, ei);
ei.attackedBy[WHITE][ALL_PIECES] |= ei.attackedBy[WHITE][KING];
ei.attackedBy[BLACK][ALL_PIECES] |= ei.attackedBy[BLACK][KING];
// Do not include in mobility squares protected by enemy pawns or occupied by our pawns or king
Bitboard mobilityArea[] = { ~(ei.attackedBy[BLACK][PAWN] | pos.pieces(WHITE, PAWN, KING)),
~(ei.attackedBy[WHITE][PAWN] | pos.pieces(BLACK, PAWN, KING)) };
// Evaluate pieces and mobility
score += evaluate_pieces<KNIGHT, WHITE, Trace>(pos, ei, mobility, mobilityArea);
score += (mobility[WHITE] - mobility[BLACK]) * Weights[Mobility];
// Evaluate kings after all other pieces because we need complete attack
// information when computing the king safety evaluation.
score += evaluate_king<WHITE, Trace>(pos, ei)
- evaluate_king<BLACK, Trace>(pos, ei);
// Evaluate tactical threats, we need full attack information including king
score += evaluate_threats<WHITE, Trace>(pos, ei)
- evaluate_threats<BLACK, Trace>(pos, ei);
// Evaluate passed pawns, we need full attack information including king
score += evaluate_passed_pawns<WHITE, Trace>(pos, ei)
- evaluate_passed_pawns<BLACK, Trace>(pos, ei);
// If both sides have only pawns, score for potential unstoppable pawns
if (!pos.non_pawn_material(WHITE) && !pos.non_pawn_material(BLACK))
{
Bitboard b;
if ((b = ei.pi->passed_pawns(WHITE)) != 0)
score += int(relative_rank(WHITE, frontmost_sq(WHITE, b))) * Unstoppable;
if ((b = ei.pi->passed_pawns(BLACK)) != 0)
score -= int(relative_rank(BLACK, frontmost_sq(BLACK, b))) * Unstoppable;
}
// Evaluate space for both sides, only during opening
if (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) >= 11756)
score += (evaluate_space<WHITE>(pos, ei) - evaluate_space<BLACK>(pos, ei)) * Weights[Space];
// Scale winning side if position is more drawish than it appears
Color strongSide = eg_value(score) > VALUE_DRAW ? WHITE : BLACK;
ScaleFactor sf = ei.mi->scale_factor(pos, strongSide);
// If we don't already have an unusual scale factor, check for certain
// types of endgames, and use a lower scale for those.
if ( ei.mi->game_phase() < PHASE_MIDGAME
&& (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
{
if (pos.opposite_bishops())
{
// Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
// is almost a draw, in case of KBP vs KB is even more a draw.
if ( pos.non_pawn_material(WHITE) == BishopValueMg
&& pos.non_pawn_material(BLACK) == BishopValueMg)
sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(32) : ScaleFactor(8);
// Endgame with opposite-colored bishops, but also other pieces. Still
// a bit drawish, but not as drawish as with only the two bishops.
else
sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
}
// Endings where weaker side can place his king in front of the opponent's
// pawns are drawish.
else if ( abs(eg_value(score)) <= BishopValueEg
&& ei.pi->pawn_span(strongSide) <= 1
&& !pos.pawn_passed(~strongSide, pos.king_square(~strongSide)))
sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(56) : ScaleFactor(38);
}
// Interpolate between a middlegame and a (scaled by 'sf') endgame score
Value v = mg_value(score) * int(ei.mi->game_phase())
+ eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
v /= int(PHASE_MIDGAME);
// In case of tracing add all single evaluation terms for both white and black
if (Trace)
{
Tracing::write(Tracing::MATERIAL, pos.psq_score());
Tracing::write(Tracing::IMBALANCE, ei.mi->imbalance());
Tracing::write(PAWN, ei.pi->pawns_score());
Tracing::write(Tracing::MOBILITY, mobility[WHITE] * Weights[Mobility]
, mobility[BLACK] * Weights[Mobility]);
Tracing::write(Tracing::SPACE, evaluate_space<WHITE>(pos, ei) * Weights[Space]
, evaluate_space<BLACK>(pos, ei) * Weights[Space]);
Tracing::write(Tracing::TOTAL, score);
}
return (pos.side_to_move() == WHITE ? v : -v) + Eval::Tempo; // Side to move point of view
}
// Tracing functions
double Tracing::to_cp(Value v) { return double(v) / PawnValueEg; }
void Tracing::write(int idx, Color c, Score s) { scores[c][idx] = s; }
void Tracing::write(int idx, Score w, Score b) {
scores[WHITE][idx] = w, scores[BLACK][idx] = b;
}
std::ostream& Tracing::operator<<(std::ostream& os, Term t) {
double wScore[] = { to_cp(mg_value(scores[WHITE][t])), to_cp(eg_value(scores[WHITE][t])) };
double bScore[] = { to_cp(mg_value(scores[BLACK][t])), to_cp(eg_value(scores[BLACK][t])) };
if (t == MATERIAL || t == IMBALANCE || t == Term(PAWN) || t == TOTAL)
os << " --- --- | --- --- | ";
else
os << std::setw(5) << wScore[MG] << " " << std::setw(5) << wScore[EG] << " | "
<< std::setw(5) << bScore[MG] << " " << std::setw(5) << bScore[EG] << " | ";
os << std::setw(5) << wScore[MG] - bScore[MG] << " "
<< std::setw(5) << wScore[EG] - bScore[EG] << " \n";
return os;
}
std::string Tracing::do_trace(const Position& pos) {
std::memset(scores, 0, sizeof(scores));
Value v = do_evaluate<true>(pos);
v = pos.side_to_move() == WHITE ? v : -v; // White's point of view
std::stringstream ss;
ss << std::showpoint << std::noshowpos << std::fixed << std::setprecision(2)
<< " Eval term | White | Black | Total \n"
<< " | MG EG | MG EG | MG EG \n"
<< "----------------+-------------+-------------+-------------\n"
<< " Material | " << Term(MATERIAL)
<< " Imbalance | " << Term(IMBALANCE)
<< " Pawns | " << Term(PAWN)
<< " Knights | " << Term(KNIGHT)
<< " Bishop | " << Term(BISHOP)
<< " Rooks | " << Term(ROOK)
<< " Queens | " << Term(QUEEN)
<< " Mobility | " << Term(MOBILITY)
<< " King safety | " << Term(KING)
<< " Threats | " << Term(THREAT)
<< " Passed pawns | " << Term(PASSED)
<< " Space | " << Term(SPACE)
<< "----------------+-------------+-------------+-------------\n"
<< " Total | " << Term(TOTAL);
ss << "\nTotal Evaluation: " << to_cp(v) << " (white side)\n";
return ss.str();
}
} // namespace
namespace Eval {
/// evaluate() is the main evaluation function. It returns a static evaluation
/// of the position always from the point of view of the side to move.
Value evaluate(const Position& pos) {
return do_evaluate<false>(pos);
}
/// trace() is like evaluate(), but instead of returning a value, it returns
/// a string (suitable for outputting to stdout) that contains the detailed
/// descriptions and values of each evaluation term. It's mainly used for
/// debugging.
std::string trace(const Position& pos) {
return Tracing::do_trace(pos);
}
/// init() computes evaluation weights, usually at startup
void init() {
const int MaxSlope = 8700;
const int Peak = 1280000;
int t = 0;
for (int i = 0; i < 400; ++i)
{
t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
KingDanger[i] = make_score(t / 1000, 0) * Weights[KingSafety];
}
}
} // namespace Eval
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