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BadFish/src/evaluate.cpp
Marco Costalba 4f7ec4128f Retire count_1s_8bit() 
Use the plain array lookup in the only place where it
is used. This remove an unecessary indirection and better
clarifies what code does.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
2009-05-19 15:49:54 +01:00

1224 lines
46 KiB
C++
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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) 2008-2009 Marco Costalba
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 "evaluate.h"
#include "material.h"
#include "pawns.h"
#include "scale.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 = 4;
// Evaluation weights, initialized from UCI options
int WeightMobilityMidgame, WeightMobilityEndgame;
int WeightPawnStructureMidgame, WeightPawnStructureEndgame;
int WeightPassedPawnsMidgame, WeightPassedPawnsEndgame;
int WeightKingSafety[2];
int WeightSpace;
// 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 int WeightMobilityMidgameInternal = 0x0FA;
const int WeightMobilityEndgameInternal = 0x10A;
const int WeightPawnStructureMidgameInternal = 0x0EC;
const int WeightPawnStructureEndgameInternal = 0x0CD;
const int WeightPassedPawnsMidgameInternal = 0x108;
const int WeightPassedPawnsEndgameInternal = 0x109;
const int WeightKingSafetyInternal = 0x0F7;
const int WeightKingOppSafetyInternal = 0x101;
const int WeightSpaceInternal = 0x02F;
// Visually better to define tables constants
typedef Value V;
// Knight mobility bonus in middle game and endgame, indexed by the number
// of attacked squares not occupied by friendly piecess.
const Value MidgameKnightMobilityBonus[] = {
// 0 1 2 3 4 5 6 7 8
V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
};
const Value EndgameKnightMobilityBonus[] = {
// 0 1 2 3 4 5 6 7 8
V(-30), V(-20),V(-10), V(0), V(10), V(20), V(25), V(30), V(30)
};
// 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 Value MidgameBishopMobilityBonus[] = {
// 0 1 2 3 4 5 6 7
V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
// 8 9 10 11 12 13 14 15
V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
};
const Value EndgameBishopMobilityBonus[] = {
// 0 1 2 3 4 5 6 7
V(-30), V(-15), V(0), V(15), V(30), V(45), V(58), V(66),
// 8 9 10 11 12 13 14 15
V( 72), V( 76), V(78), V(80), V(81), V(82), V(83), V(83)
};
// 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 Value MidgameRookMobilityBonus[] = {
// 0 1 2 3 4 5 6 7
V(-18), V(-12), V(-6), V(0), V(6), V(12), V(16), V(21),
// 8 9 10 11 12 13 14 15
V( 24), V( 27), V(28), V(29), V(30), V(31), V(32), V(33)
};
const Value EndgameRookMobilityBonus[] = {
// 0 1 2 3 4 5 6 7
V(-30), V(-18), V(-6), V(6), V(18), V(30), V(42), V(54),
// 8 9 10 11 12 13 14 15
V( 66), V( 74), V(78), V(80), V(81), V(82), V(83), V(83)
};
// Queen mobility bonus in middle game and endgame, indexed by the number
// of attacked squares not occupied by friendly pieces.
const Value MidgameQueenMobilityBonus[] = {
// 0 1 2 3 4 5 6 7
V(-10), V(-8), V(-6), V(-4), V(-2), V( 0), V( 2), V( 4),
// 8 9 10 11 12 13 14 15
V( 6), V( 8), V(10), V(12), V(13), V(14), V(15), V(16),
// 16 17 18 19 20 21 22 23
V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16),
// 24 25 26 27 28 29 30 31
V( 16), V(16), V(16), V(16), V(16), V(16), V(16), V(16)
};
const Value EndgameQueenMobilityBonus[] = {
// 0 1 2 3 4 5 6 7
V(-20),V(-15),V(-10), V(-5), V( 0), V( 5), V(10), V(15),
// 8 9 10 11 12 13 14 15
V( 19), V(23), V(27), V(29), V(30), V(30), V(30), V(30),
// 16 17 18 19 20 21 22 23
V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30),
// 24 25 26 27 28 29 30 31
V( 30), V(30), V(30), V(30), V(30), V(30), V(30), V(30)
};
// 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(5),V(10),V(10), V(5), V(0), V(0), // 3
V(0), V(5),V(20),V(30),V(30),V(20), V(5), V(0), // 4
V(0),V(10),V(30),V(40),V(40),V(30),V(10), V(0), // 5
V(0), V(5),V(20),V(20),V(20),V(20), 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
};
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(20),V(20),V(20),V(20),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
};
// Bonus for unstoppable passed pawns
const Value UnstoppablePawnValue = Value(0x500);
// Rooks and queens on the 7th rank
const Value MidgameRookOn7thBonus = Value(47);
const Value EndgameRookOn7thBonus = Value(98);
const Value MidgameQueenOn7thBonus = Value(27);
const Value EndgameQueenOn7thBonus = Value(54);
// Rooks on open files
const Value RookOpenFileBonus = Value(43);
const Value RookHalfOpenFileBonus = Value(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 Value TrappedBishopA7H7Penalty = Value(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 Value TrappedBishopA1H1Penalty = Value(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 area of the board which is consdered 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 safety constants and variables. The king safety scores are taken
/// from the array SafetyTable[]. Various little "meta-bonuses" measuring
/// the strength of the attack are added up into an integer, which is used
/// as an index to SafetyTable[].
// Attack weights for each piece type
const int QueenAttackWeight = 5;
const int RookAttackWeight = 3;
const int BishopAttackWeight = 2;
const int KnightAttackWeight = 2;
// Bonuses for safe checks, initialized from UCI options
int QueenContactCheckBonus, DiscoveredCheckBonus;
int QueenCheckBonus, RookCheckBonus, BishopCheckBonus, KnightCheckBonus;
// Scan for queen contact mates?
const bool QueenContactMates = true;
// Bonus for having a mate threat, initialized from UCI options
int MateThreatBonus;
// 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
};
// SafetyTable[] contains the actual king safety scores. It is initialized
// in init_safety().
Value SafetyTable[100];
// Pawn and material hash tables, indexed by the current thread id
PawnInfoTable* PawnTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
MaterialInfoTable* MaterialTable[8] = {0, 0, 0, 0, 0, 0, 0, 0};
// Sizes of pawn and material hash tables
const int PawnTableSize = 16384;
const int MaterialTableSize = 1024;
// Array which gives the number of nonzero bits in an 8-bit integer
uint8_t BitCount8Bit[256];
// Function prototypes
template<PieceType Piece>
void evaluate_pieces(const Position& p, Color us, EvalInfo& ei);
template<>
void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo &ei);
void evaluate_passed_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);
void evaluate_space(const Position &p, Color us, EvalInfo &ei);
inline Value apply_weight(Value v, int w);
Value scale_by_game_phase(Value mv, Value ev, Phase ph, const ScaleFactor sf[]);
int compute_weight(int uciWeight, int internalWeight);
int weight_option(const std::string& opt, int weight);
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, int threadID) {
assert(pos.is_ok());
assert(threadID >= 0 && threadID < THREAD_MAX);
memset(&ei, 0, sizeof(EvalInfo));
// Initialize by reading the incrementally updated scores included in the
// position object (material + piece square tables)
ei.mgValue = pos.mg_value();
ei.egValue = pos.eg_value();
// Probe the material hash table
ei.mi = MaterialTable[threadID]->get_material_info(pos);
ei.mgValue += ei.mi->mg_value();
ei.egValue += ei.mi->eg_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
ScaleFactor factor[2];
factor[WHITE] = ei.mi->scale_factor(pos, WHITE);
factor[BLACK] = ei.mi->scale_factor(pos, BLACK);
// Probe the pawn hash table
ei.pi = PawnTable[threadID]->get_pawn_info(pos);
ei.mgValue += apply_weight(ei.pi->mg_value(), WeightPawnStructureMidgame);
ei.egValue += apply_weight(ei.pi->eg_value(), WeightPawnStructureEndgame);
// Initialize king attack bitboards and king attack zones for both sides
ei.attackedBy[WHITE][KING] = pos.piece_attacks<KING>(pos.king_square(WHITE));
ei.attackedBy[BLACK][KING] = pos.piece_attacks<KING>(pos.king_square(BLACK));
ei.kingZone[WHITE] = ei.attackedBy[BLACK][KING] | (ei.attackedBy[BLACK][KING] >> 8);
ei.kingZone[BLACK] = ei.attackedBy[WHITE][KING] | (ei.attackedBy[WHITE][KING] << 8);
// Initialize pawn attack bitboards for both sides
ei.attackedBy[WHITE][PAWN] = ((pos.pawns(WHITE) << 9) & ~FileABB) | ((pos.pawns(WHITE) << 7) & ~FileHBB);
ei.attackedBy[BLACK][PAWN] = ((pos.pawns(BLACK) >> 7) & ~FileABB) | ((pos.pawns(BLACK) >> 9) & ~FileHBB);
ei.kingAttackersCount[WHITE] = count_1s_max_15(ei.attackedBy[WHITE][PAWN] & ei.attackedBy[BLACK][KING])/2;
ei.kingAttackersCount[BLACK] = count_1s_max_15(ei.attackedBy[BLACK][PAWN] & ei.attackedBy[WHITE][KING])/2;
// Evaluate pieces
for (Color c = WHITE; c <= BLACK; c++)
{
evaluate_pieces<KNIGHT>(pos, c, ei);
evaluate_pieces<BISHOP>(pos, c, ei);
evaluate_pieces<ROOK>(pos, c, ei);
evaluate_pieces<QUEEN>(pos, c, ei);
// Sum up all attacked squares
ei.attackedBy[c][0] = ei.attackedBy[c][PAWN] | ei.attackedBy[c][KNIGHT]
| ei.attackedBy[c][BISHOP] | ei.attackedBy[c][ROOK]
| ei.attackedBy[c][QUEEN] | ei.attackedBy[c][KING];
}
// 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.
for (Color c = WHITE; c <= BLACK; c++)
evaluate_pieces<KING>(pos, c, ei);
// Evaluate passed pawns. We evaluate passed pawns for both sides at once,
// because we need to know which side promotes first in positions where
// both sides have an unstoppable passed pawn.
if (ei.pi->passed_pawns())
evaluate_passed_pawns(pos, ei);
Phase phase = pos.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.mgValue += ei.pi->queenside_storm_value(WHITE)
- ei.pi->kingside_storm_value(BLACK);
else if ( square_file(pos.king_square(WHITE)) <= FILE_D
&& square_file(pos.king_square(BLACK)) >= FILE_E)
ei.mgValue += ei.pi->kingside_storm_value(WHITE)
- ei.pi->queenside_storm_value(BLACK);
// Evaluate space for both sides
if (ei.mi->space_weight() > 0)
{
evaluate_space(pos, WHITE, ei);
evaluate_space(pos, BLACK, ei);
}
}
// Mobility
ei.mgValue += apply_weight(ei.mgMobility, WeightMobilityMidgame);
ei.egValue += apply_weight(ei.egMobility, WeightMobilityEndgame);
// 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 && ei.egValue > Value(0))
|| (factor[BLACK] == SCALE_FACTOR_NORMAL && ei.egValue < 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, and
// return
Color stm = pos.side_to_move();
Value v = Sign[stm] * scale_by_game_phase(ei.mgValue, ei.egValue, phase, factor);
return (ei.mateThreat[stm] == MOVE_NONE ? v : 8 * QueenValueMidgame - v);
}
/// quick_evaluate() does a very approximate evaluation of the current position.
/// It currently considers only material and piece square table scores. Perhaps
/// we should add scores from the pawn and material hash tables?
Value quick_evaluate(const Position &pos) {
assert(pos.is_ok());
static const
ScaleFactor sf[2] = {SCALE_FACTOR_NORMAL, SCALE_FACTOR_NORMAL};
Value mgv = pos.mg_value();
Value egv = pos.eg_value();
Phase ph = pos.game_phase();
Color stm = pos.side_to_move();
return Sign[stm] * scale_by_game_phase(mgv, egv, ph, sf);
}
/// init_eval() initializes various tables used by the evaluation function.
void init_eval(int threads) {
assert(threads <= THREAD_MAX);
for (int i = 0; i < THREAD_MAX; 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);
}
for (Bitboard b = 0ULL; b < 256ULL; b++)
{
assert(count_1s(b) == int(uint8_t(count_1s(b))));
BitCount8Bit[b] = (uint8_t)count_1s(b);
}
}
/// quit_eval() releases heap-allocated memory at program termination.
void quit_eval() {
for (int i = 0; i < THREAD_MAX; 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) {
WeightMobilityMidgame = weight_option("Mobility (Middle Game)", WeightMobilityMidgameInternal);
WeightMobilityEndgame = weight_option("Mobility (Endgame)", WeightMobilityEndgameInternal);
WeightPawnStructureMidgame = weight_option("Pawn Structure (Middle Game)", WeightPawnStructureMidgameInternal);
WeightPawnStructureEndgame = weight_option("Pawn Structure (Endgame)", WeightPawnStructureEndgameInternal);
WeightPassedPawnsMidgame = weight_option("Passed Pawns (Middle Game)", WeightPassedPawnsMidgameInternal);
WeightPassedPawnsEndgame = weight_option("Passed Pawns (Endgame)", WeightPassedPawnsEndgameInternal);
Color them = opposite_color(us);
WeightKingSafety[us] = weight_option("Cowardice", WeightKingSafetyInternal);
WeightKingSafety[them] = weight_option("Aggressiveness", WeightKingOppSafetyInternal);
WeightSpace = weight_option("Space", WeightSpaceInternal);
init_safety();
}
namespace {
// evaluate_common() computes terms common to all pieces attack
template<PieceType Piece>
int evaluate_common(const Position& p, const Bitboard& b, Color us, EvalInfo& ei, Square s = SQ_NONE) {
static const int AttackWeight[] = { 0, 0, KnightAttackWeight, BishopAttackWeight, RookAttackWeight, QueenAttackWeight };
static const Value* MgBonus[] = { 0, 0, MidgameKnightMobilityBonus, MidgameBishopMobilityBonus, MidgameRookMobilityBonus, MidgameQueenMobilityBonus };
static const Value* EgBonus[] = { 0, 0, EndgameKnightMobilityBonus, EndgameBishopMobilityBonus, EndgameRookMobilityBonus, EndgameQueenMobilityBonus };
static const Value* OutpostBonus[] = { 0, 0, KnightOutpostBonus, BishopOutpostBonus, 0, 0 };
Color them = opposite_color(us);
// Update attack info
ei.attackedBy[us][Piece] |= b;
// King attack
if (b & ei.kingZone[us])
{
ei.kingAttackersCount[us]++;
ei.kingAttackersWeight[us] += AttackWeight[Piece];
Bitboard bb = (b & ei.attackedBy[them][KING]);
if (bb)
ei.kingAdjacentZoneAttacksCount[us] += count_1s_max_15(bb);
}
// Remove squares protected by enemy pawns
Bitboard bb = (b & ~ei.attackedBy[them][PAWN]);
// Mobility
int mob = (Piece != QUEEN ? count_1s_max_15(bb & ~p.pieces_of_color(us))
: count_1s(bb & ~p.pieces_of_color(us)));
ei.mgMobility += Sign[us] * MgBonus[Piece][mob];
ei.egMobility += Sign[us] * EgBonus[Piece][mob];
// Bishop and Knight outposts
if ( (Piece == BISHOP || Piece == KNIGHT) // compile time condition
&& p.square_is_weak(s, them))
{
// Initial bonus based on square
Value v, bonus;
v = bonus = OutpostBonus[Piece][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 (v && (p.pawn_attacks(them, s) & p.pawns(us)))
{
bonus += v / 2;
if ( p.piece_count(them, KNIGHT) == 0
&& (SquaresByColorBB[square_color(s)] & p.bishops(them)) == EmptyBoardBB)
bonus += v;
}
ei.mgValue += Sign[us] * bonus;
ei.egValue += Sign[us] * bonus;
}
return mob;
}
// evaluate_pieces<>() assigns bonuses and penalties to the pieces of a given
// color.
template<PieceType Piece>
void evaluate_pieces(const Position& pos, Color us, EvalInfo& ei) {
Bitboard b;
Square s, ksq;
Color them;
int mob;
File f;
for (int i = 0, e = pos.piece_count(us, Piece); i < e; i++)
{
s = pos.piece_list(us, Piece, i);
if (Piece == KNIGHT || Piece == QUEEN)
b = pos.piece_attacks<Piece>(s);
else if (Piece == BISHOP)
b = bishop_attacks_bb(s, pos.occupied_squares() & ~pos.queens(us));
else if (Piece == ROOK)
b = rook_attacks_bb(s, pos.occupied_squares() & ~pos.rooks_and_queens(us));
// Attacks, mobility and outposts
mob = evaluate_common<Piece>(pos, b, us, 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);
}
if (Piece == ROOK || Piece == QUEEN)
{
// Queen or rook on 7th rank
them = opposite_color(us);
if ( relative_rank(us, s) == RANK_7
&& relative_rank(us, pos.king_square(them)) == RANK_8)
{
ei.mgValue += Sign[us] * (Piece == ROOK ? MidgameRookOn7thBonus : MidgameQueenOn7thBonus);
ei.egValue += Sign[us] * (Piece == ROOK ? EndgameRookOn7thBonus : EndgameQueenOn7thBonus);
}
}
// 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.mgValue += Sign[us] * RookOpenFileBonus;
ei.egValue += Sign[us] * RookOpenFileBonus;
}
else
{
ei.mgValue += Sign[us] * RookHalfOpenFileBonus;
ei.egValue += 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.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
: Sign[us] * (TrappedRookPenalty - mob * 16);
}
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.mgValue -= pos.can_castle(us)? Sign[us] * ((TrappedRookPenalty - mob * 16) / 2)
: Sign[us] * (TrappedRookPenalty - mob * 16);
}
}
}
}
inline Bitboard shiftRowsDown(const Bitboard& b, int num) {
return b >> (num << 3);
}
// evaluate_pieces<KING>() assigns bonuses and penalties to a king of a given
// color.
template<>
void evaluate_pieces<KING>(const Position& p, Color us, EvalInfo& ei) {
int shelter = 0, sign = Sign[us];
Square s = p.king_square(us);
// King shelter
if (relative_rank(us, s) <= RANK_4)
{
// Shelter cache lookup
shelter = ei.pi->kingShelter(us, s);
if (shelter == -1)
{
shelter = 0;
Bitboard pawns = p.pawns(us) & this_and_neighboring_files_bb(s);
Rank r = square_rank(s);
for (int i = 1; i < 4; i++)
shelter += BitCount8Bit[shiftRowsDown(pawns, r+i*sign) & 0xFF] * (128 >> i);
// Cache shelter value in pawn info
ei.pi->setKingShelter(us, s, shelter);
}
ei.mgValue += sign * Value(shelter);
}
// King safety. This is quite complicated, and is almost certainly far
// from optimally tuned.
Color them = opposite_color(us);
if ( p.piece_count(them, QUEEN) >= 1
&& ei.kingAttackersCount[them] >= 2
&& p.non_pawn_material(them) >= QueenValueMidgame + RookValueMidgame
&& ei.kingAdjacentZoneAttacksCount[them])
{
// Is it the attackers turn to move?
bool sente = (them == p.side_to_move());
// Find the attacked squares around the king which has no defenders
// apart from the king itself
Bitboard undefended =
ei.attacked_by(them) & ~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)
& ei.attacked_by(us, KING);
Bitboard occ = p.occupied_squares(), b, b2;
// Initialize the 'attackUnits' variable, which is used later on as an
// index to the SafetyTable[] array. The initial value is based on the
// number and types of the attacking pieces, the number of attacked and
// undefended squares around the king, the square of the king, and the
// quality of the pawn shelter.
int attackUnits =
Min((ei.kingAttackersCount[them] * ei.kingAttackersWeight[them]) / 2, 25)
+ (ei.kingAdjacentZoneAttacksCount[them] + count_1s_max_15(undefended)) * 3
+ InitKingDanger[relative_square(us, s)] - (shelter >> 5);
// Analyse safe queen contact checks
b = undefended & ei.attacked_by(them, QUEEN) & ~p.pieces_of_color(them);
if (b)
{
Bitboard attackedByOthers =
ei.attacked_by(them, PAWN) | ei.attacked_by(them, KNIGHT)
| ei.attacked_by(them, BISHOP) | ei.attacked_by(them, ROOK);
b &= attackedByOthers;
if (b)
{
// The bitboard b now contains the squares available for safe queen
// contact checks.
int count = count_1s_max_15(b);
attackUnits += QueenContactCheckBonus * count * (sente ? 2 : 1);
// Is there a mate threat?
if (QueenContactMates && !p.is_check())
{
Bitboard escapeSquares =
p.piece_attacks<KING>(s) & ~p.pieces_of_color(us) & ~attackedByOthers;
while (b)
{
Square from, to = pop_1st_bit(&b);
if (!(escapeSquares & ~queen_attacks_bb(to, occ & ClearMaskBB[s])))
{
// We have a mate, unless the queen is pinned or there
// is an X-ray attack through the queen.
for (int i = 0; i < p.piece_count(them, QUEEN); i++)
{
from = p.piece_list(them, QUEEN, i);
if ( bit_is_set(p.piece_attacks<QUEEN>(from), to)
&& !bit_is_set(p.pinned_pieces(them), from)
&& !(rook_attacks_bb(to, occ & ClearMaskBB[from]) & p.rooks_and_queens(us))
&& !(bishop_attacks_bb(to, occ & ClearMaskBB[from]) & p.bishops_and_queens(us)))
ei.mateThreat[them] = make_move(from, to);
}
}
}
}
}
}
// Analyse safe distance checks
if (QueenCheckBonus > 0 || RookCheckBonus > 0)
{
b = p.piece_attacks<ROOK>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
// Queen checks
b2 = b & ei.attacked_by(them, QUEEN);
if( b2)
attackUnits += QueenCheckBonus * count_1s_max_15(b2);
// Rook checks
b2 = b & ei.attacked_by(them, ROOK);
if (b2)
attackUnits += RookCheckBonus * count_1s_max_15(b2);
}
if (QueenCheckBonus > 0 || BishopCheckBonus > 0)
{
b = p.piece_attacks<BISHOP>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
// Queen checks
b2 = b & ei.attacked_by(them, QUEEN);
if (b2)
attackUnits += QueenCheckBonus * count_1s_max_15(b2);
// Bishop checks
b2 = b & ei.attacked_by(them, BISHOP);
if (b2)
attackUnits += BishopCheckBonus * count_1s_max_15(b2);
}
if (KnightCheckBonus > 0)
{
b = p.piece_attacks<KNIGHT>(s) & ~p.pieces_of_color(them) & ~ei.attacked_by(us);
// Knight checks
b2 = b & ei.attacked_by(them, KNIGHT);
if (b2)
attackUnits += KnightCheckBonus * count_1s_max_15(b2);
}
// Analyse discovered checks (only for non-pawns right now, consider
// adding pawns later).
if (DiscoveredCheckBonus)
{
b = p.discovered_check_candidates(them) & ~p.pawns();
if (b)
attackUnits += DiscoveredCheckBonus * count_1s_max_15(b) * (sente? 2 : 1);
}
// Has a mate threat been found? We don't do anything here if the
// side with the mating move is the side to move, because in that
// case the mating side will get a huge bonus at the end of the main
// evaluation function instead.
if (ei.mateThreat[them] != MOVE_NONE)
attackUnits += MateThreatBonus;
// Ensure that attackUnits is between 0 and 99, in order to avoid array
// out of bounds errors:
if (attackUnits < 0)
attackUnits = 0;
if (attackUnits >= 100)
attackUnits = 99;
// Finally, extract the king safety score from the SafetyTable[] array.
// Add the score to the evaluation, and also to ei.futilityMargin. The
// reason for adding the king safety score to the futility margin is
// that the king safety scores can sometimes be very big, and that
// capturing a single attacking piece can therefore result in a score
// change far bigger than the value of the captured piece.
Value v = apply_weight(SafetyTable[attackUnits], WeightKingSafety[us]);
ei.mgValue -= sign * v;
if (us == p.side_to_move())
ei.futilityMargin += v;
}
}
// evaluate_passed_pawns() evaluates the passed pawns for both sides.
void evaluate_passed_pawns(const Position &pos, EvalInfo &ei) {
bool hasUnstoppable[2] = {false, false};
int movesToGo[2] = {100, 100};
for (Color us = WHITE; us <= BLACK; us++)
{
Color them = opposite_color(us);
Square ourKingSq = pos.king_square(us);
Square theirKingSq = pos.king_square(them);
Bitboard b = ei.pi->passed_pawns() & pos.pawns(us), b2, b3, b4;
while (b)
{
Square s = pop_1st_bit(&b);
assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
assert(pos.pawn_is_passed(us, s));
int r = int(relative_rank(us, s) - RANK_2);
int tr = Max(0, r * (r - 1));
Square blockSq = s + pawn_push(us);
// Base bonus based on rank
Value mbonus = Value(20 * tr);
Value ebonus = Value(10 + r * r * 10);
// Adjust bonus based on king proximity
if (tr != 0)
{
ebonus -= Value(square_distance(ourKingSq, blockSq) * 3 * tr);
ebonus -= Value(square_distance(ourKingSq, blockSq + pawn_push(us)) * 1 * tr);
ebonus += Value(square_distance(theirKingSq, blockSq) * 6 * tr);
// If the pawn is free to advance, increase bonus
if (pos.square_is_empty(blockSq))
{
b2 = squares_in_front_of(us, s);
b3 = b2 & ei.attacked_by(them);
b4 = b2 & 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.
if ( bit_is_set(ei.attacked_by(them,ROOK) | ei.attacked_by(them,QUEEN),s)
&& (squares_behind(us, s) & pos.rooks_and_queens(them)))
b3 = b2;
if ((b2 & pos.pieces_of_color(them)) == EmptyBoardBB)
{
// There are no enemy pieces in the pawn's path! Are any of the
// squares in the pawn's path attacked by the enemy?
if (b3 == EmptyBoardBB)
// No enemy attacks, huge bonus!
ebonus += Value(tr * (b2 == b4 ? 17 : 15));
else
// OK, there are enemy attacks. 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 * ((b3 & b4) == b3 ? 13 : 8));
}
else
{
// There are some enemy pieces in the pawn's path. While this is
// sad, we still assign a moderate bonus if all squares in the path
// which are either occupied by or attacked by enemy pieces are
// also attacked by us.
if (((b3 | (b2 & pos.pieces_of_color(them))) & ~b4) == EmptyBoardBB)
ebonus += Value(tr * 6);
}
// At last, add a small bonus when there are no *friendly* pieces
// in the pawn's path.
if ((b2 & pos.pieces_of_color(us)) == EmptyBoardBB)
ebonus += Value(tr);
}
}
// If the pawn is supported by a friendly pawn, increase bonus
b2 = pos.pawns(us) & neighboring_files_bb(s);
if (b2 & rank_bb(s))
ebonus += Value(r * 20);
else if (pos.pawn_attacks(them, s) & b2)
ebonus += Value(r * 12);
// If the other side has only a king, check whether the pawn is
// unstoppable
if (pos.non_pawn_material(them) == Value(0))
{
Square qsq;
int d;
qsq = relative_square(us, make_square(square_file(s), RANK_8));
d = square_distance(s, qsq)
- square_distance(theirKingSq, qsq)
+ (us != pos.side_to_move());
if (d < 0)
{
int mtg = RANK_8 - relative_rank(us, s);
int blockerCount = count_1s_max_15(squares_in_front_of(us,s) & pos.occupied_squares());
mtg += blockerCount;
d += blockerCount;
if (d < 0)
{
hasUnstoppable[us] = true;
movesToGo[us] = Min(movesToGo[us], mtg);
}
}
}
// 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
&& pos.piece_count(them, KNIGHT) <= 1)
ebonus += ebonus / 4;
else if(pos.rooks_and_queens(them))
ebonus -= ebonus / 4;
}
// Add the scores for this pawn to the middle game and endgame eval.
ei.mgValue += apply_weight(Sign[us] * mbonus, WeightPassedPawnsMidgame);
ei.egValue += apply_weight(Sign[us] * ebonus, WeightPassedPawnsEndgame);
}
}
// Does either side have an unstoppable passed pawn?
if (hasUnstoppable[WHITE] && !hasUnstoppable[BLACK])
ei.egValue += UnstoppablePawnValue - Value(0x40 * movesToGo[WHITE]);
else if (hasUnstoppable[BLACK] && !hasUnstoppable[WHITE])
ei.egValue -= UnstoppablePawnValue - Value(0x40 * movesToGo[BLACK]);
else if (hasUnstoppable[BLACK] && hasUnstoppable[WHITE])
{
// 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()]--;
// If one side queens at least three plies before the other, that
// side wins.
if (movesToGo[WHITE] <= movesToGo[BLACK] - 3)
ei.egValue += UnstoppablePawnValue - Value(0x40 * (movesToGo[WHITE]/2));
else if(movesToGo[BLACK] <= movesToGo[WHITE] - 3)
ei.egValue -= UnstoppablePawnValue - Value(0x40 * (movesToGo[BLACK]/2));
// We could also add some rules about the situation when one side
// queens exactly one ply before the other: Does the first queen
// check the opponent's king, or attack the opponent's queening square?
// This is slightly tricky to get right, because it is possible that
// the opponent's king has moved somewhere before the first pawn queens.
}
}
// 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.mgValue -= Sign[us] * TrappedBishopA7H7Penalty;
ei.egValue -= 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)
{
Value penalty;
if (!pos.square_is_empty(b3))
penalty = 2*TrappedBishopA1H1Penalty;
else if (pos.piece_on(c3) == pawn)
penalty = TrappedBishopA1H1Penalty;
else
penalty = TrappedBishopA1H1Penalty / 2;
ei.mgValue -= Sign[us] * penalty;
ei.egValue -= 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.
void evaluate_space(const Position &pos, Color us, EvalInfo &ei) {
Color them = opposite_color(us);
// Find the safe squares for our pieces inside the area defined by
// SpaceMask[us]. A square is unsafe it is attacked by an enemy
// pawn, or if it is undefended and attacked by an enemy piece.
Bitboard safeSquares = SpaceMask[us]
& ~pos.pawns(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 behindFriendlyPawns = pos.pawns(us);
if (us == WHITE)
{
behindFriendlyPawns |= (behindFriendlyPawns >> 8);
behindFriendlyPawns |= (behindFriendlyPawns >> 16);
}
else
{
behindFriendlyPawns |= (behindFriendlyPawns << 8);
behindFriendlyPawns |= (behindFriendlyPawns << 16);
}
int space = count_1s_max_15(safeSquares)
+ count_1s_max_15(behindFriendlyPawns & safeSquares);
ei.mgValue += Sign[us] * apply_weight(Value(space * ei.mi->space_weight()), WeightSpace);
}
// apply_weight() applies an evaluation weight to a value
inline Value apply_weight(Value v, int w) {
return (v*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(Value mv, Value ev, Phase ph, const ScaleFactor sf[]) {
assert(mv > -VALUE_INFINITE && mv < VALUE_INFINITE);
assert(ev > -VALUE_INFINITE && ev < VALUE_INFINITE);
assert(ph >= PHASE_ENDGAME && ph <= PHASE_MIDGAME);
ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));
return Value(int(result) & ~(GrainSize - 1));
}
// compute_weight() computes the value of an evaluation weight, by combining
// an UCI-configurable weight with an internal weight.
int compute_weight(int uciWeight, int internalWeight) {
uciWeight = (uciWeight * 0x100) / 100;
return (uciWeight * internalWeight) / 0x100;
}
// helper used in read_weights()
int weight_option(const std::string& opt, int weight) {
return compute_weight(get_option_value_int(opt), weight);
}
// init_safety() initizes the king safety evaluation, based on UCI
// parameters. It is called from read_weights().
void init_safety() {
QueenContactCheckBonus = get_option_value_int("Queen Contact Check Bonus");
QueenCheckBonus = get_option_value_int("Queen Check Bonus");
RookCheckBonus = get_option_value_int("Rook Check Bonus");
BishopCheckBonus = get_option_value_int("Bishop Check Bonus");
KnightCheckBonus = get_option_value_int("Knight Check Bonus");
DiscoveredCheckBonus = get_option_value_int("Discovered Check Bonus");
MateThreatBonus = get_option_value_int("Mate Threat Bonus");
int maxSlope = get_option_value_int("King Safety Max Slope");
int peak = get_option_value_int("King Safety Max Value") * 256 / 100;
double a = get_option_value_int("King Safety Coefficient") / 100.0;
double b = get_option_value_int("King Safety X Intercept");
bool quad = (get_option_value_string("King Safety Curve") == "Quadratic");
bool linear = (get_option_value_string("King Safety Curve") == "Linear");
for (int i = 0; i < 100; i++)
{
if (i < b)
SafetyTable[i] = Value(0);
else if(quad)
SafetyTable[i] = Value((int)(a * (i - b) * (i - b)));
else if(linear)
SafetyTable[i] = Value((int)(100 * a * (i - b)));
}
for (int i = 0; i < 100; i++)
{
if (SafetyTable[i+1] - SafetyTable[i] > maxSlope)
for (int j = i + 1; j < 100; j++)
SafetyTable[j] = SafetyTable[j-1] + Value(maxSlope);
if (SafetyTable[i] > Value(peak))
SafetyTable[i] = Value(peak);
}
}
}
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