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Latest commit 754fc8a May 18, 2021 History
The Tempo variable was introduced 10 years ago in our search because the
classical evaluation function was antisymmetrical in White and Black by design
to gain speed:

    Eval(White to play) = -Eval(Black to play)

Nowadays our neural networks know which side is to play in a position when
they evaluate a position and are trained on real games, so the neural network
encodes the advantage of moving as an output of search. This patch shows that
the Tempo variable is not necessary anymore.

STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 33512 W: 2805 L: 2709 D: 27998
Ptnml(0-2): 80, 2209, 12095, 2279, 93
https://tests.stockfishchess.org/tests/view/60a44ceace8ea25a3ef03d30

LTC:
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 53920 W: 1807 L: 1760 D: 50353
Ptnml(0-2): 16, 1617, 23650, 1658, 19
https://tests.stockfishchess.org/tests/view/60a477f0ce8ea25a3ef03d49

We also tried a match (20000 games) at STC using purely classical, result was neutral:
https://tests.stockfishchess.org/tests/view/60a4eebcce8ea25a3ef03db5

Note: there are two locations left in search.cpp where we assume antisymmetry
of evaluation (in relation with a speed optimization for null moves in lines
770 and 1439), but as the values are just used for heuristic pruning this
approximation should not hurt too much because the order of magnitude is still
true most of the time.

closes #3481

Bench: 4015864
45 contributors

Users who have contributed to this file

@mcostalba @vondele @snicolet @lucasart @protonspring @Rocky640 @zamar @SFisGOD @uriblass @Stefano80 @FauziAkram @syzygy1
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
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/>.
*/
#ifndef TYPES_H_INCLUDED
#define TYPES_H_INCLUDED
/// When compiling with provided Makefile (e.g. for Linux and OSX), configuration
/// is done automatically. To get started type 'make help'.
///
/// When Makefile is not used (e.g. with Microsoft Visual Studio) some switches
/// need to be set manually:
///
/// -DNDEBUG | Disable debugging mode. Always use this for release.
///
/// -DNO_PREFETCH | Disable use of prefetch asm-instruction. You may need this to
/// | run on some very old machines.
///
/// -DUSE_POPCNT | Add runtime support for use of popcnt asm-instruction. Works
/// | only in 64-bit mode and requires hardware with popcnt support.
///
/// -DUSE_PEXT | Add runtime support for use of pext asm-instruction. Works
/// | only in 64-bit mode and requires hardware with pext support.
#include <cassert>
#include <cctype>
#include <cstdint>
#include <cstdlib>
#include <algorithm>
#if defined(_MSC_VER)
// Disable some silly and noisy warning from MSVC compiler
#pragma warning(disable: 4127) // Conditional expression is constant
#pragma warning(disable: 4146) // Unary minus operator applied to unsigned type
#pragma warning(disable: 4800) // Forcing value to bool 'true' or 'false'
#endif
/// Predefined macros hell:
///
/// __GNUC__ Compiler is gcc, Clang or Intel on Linux
/// __INTEL_COMPILER Compiler is Intel
/// _MSC_VER Compiler is MSVC or Intel on Windows
/// _WIN32 Building on Windows (any)
/// _WIN64 Building on Windows 64 bit
#if defined(__GNUC__ ) && (__GNUC__ < 9 || (__GNUC__ == 9 && __GNUC_MINOR__ <= 2)) && defined(_WIN32) && !defined(__clang__)
#define ALIGNAS_ON_STACK_VARIABLES_BROKEN
#endif
#define ASSERT_ALIGNED(ptr, alignment) assert(reinterpret_cast<uintptr_t>(ptr) % alignment == 0)
#if defined(_WIN64) && defined(_MSC_VER) // No Makefile used
# include <intrin.h> // Microsoft header for _BitScanForward64()
# define IS_64BIT
#endif
#if defined(USE_POPCNT) && (defined(__INTEL_COMPILER) || defined(_MSC_VER))
# include <nmmintrin.h> // Intel and Microsoft header for _mm_popcnt_u64()
#endif
#if !defined(NO_PREFETCH) && (defined(__INTEL_COMPILER) || defined(_MSC_VER))
# include <xmmintrin.h> // Intel and Microsoft header for _mm_prefetch()
#endif
#if defined(USE_PEXT)
# include <immintrin.h> // Header for _pext_u64() intrinsic
# define pext(b, m) _pext_u64(b, m)
#else
# define pext(b, m) 0
#endif
namespace Stockfish {
#ifdef USE_POPCNT
constexpr bool HasPopCnt = true;
#else
constexpr bool HasPopCnt = false;
#endif
#ifdef USE_PEXT
constexpr bool HasPext = true;
#else
constexpr bool HasPext = false;
#endif
#ifdef IS_64BIT
constexpr bool Is64Bit = true;
#else
constexpr bool Is64Bit = false;
#endif
typedef uint64_t Key;
typedef uint64_t Bitboard;
constexpr int MAX_MOVES = 256;
constexpr int MAX_PLY = 246;
/// A move needs 16 bits to be stored
///
/// bit 0- 5: destination square (from 0 to 63)
/// bit 6-11: origin square (from 0 to 63)
/// bit 12-13: promotion piece type - 2 (from KNIGHT-2 to QUEEN-2)
/// bit 14-15: special move flag: promotion (1), en passant (2), castling (3)
/// NOTE: en passant bit is set only when a pawn can be captured
///
/// Special cases are MOVE_NONE and MOVE_NULL. We can sneak these in because in
/// any normal move destination square is always different from origin square
/// while MOVE_NONE and MOVE_NULL have the same origin and destination square.
enum Move : int {
MOVE_NONE,
MOVE_NULL = 65
};
enum MoveType {
NORMAL,
PROMOTION = 1 << 14,
EN_PASSANT = 2 << 14,
CASTLING = 3 << 14
};
enum Color {
WHITE, BLACK, COLOR_NB = 2
};
enum CastlingRights {
NO_CASTLING,
WHITE_OO,
WHITE_OOO = WHITE_OO << 1,
BLACK_OO = WHITE_OO << 2,
BLACK_OOO = WHITE_OO << 3,
KING_SIDE = WHITE_OO | BLACK_OO,
QUEEN_SIDE = WHITE_OOO | BLACK_OOO,
WHITE_CASTLING = WHITE_OO | WHITE_OOO,
BLACK_CASTLING = BLACK_OO | BLACK_OOO,
ANY_CASTLING = WHITE_CASTLING | BLACK_CASTLING,
CASTLING_RIGHT_NB = 16
};
enum Phase {
PHASE_ENDGAME,
PHASE_MIDGAME = 128,
MG = 0, EG = 1, PHASE_NB = 2
};
enum ScaleFactor {
SCALE_FACTOR_DRAW = 0,
SCALE_FACTOR_NORMAL = 64,
SCALE_FACTOR_MAX = 128,
SCALE_FACTOR_NONE = 255
};
enum Bound {
BOUND_NONE,
BOUND_UPPER,
BOUND_LOWER,
BOUND_EXACT = BOUND_UPPER | BOUND_LOWER
};
enum Value : int {
VALUE_ZERO = 0,
VALUE_DRAW = 0,
VALUE_KNOWN_WIN = 10000,
VALUE_MATE = 32000,
VALUE_INFINITE = 32001,
VALUE_NONE = 32002,
VALUE_TB_WIN_IN_MAX_PLY = VALUE_MATE - 2 * MAX_PLY,
VALUE_TB_LOSS_IN_MAX_PLY = -VALUE_TB_WIN_IN_MAX_PLY,
VALUE_MATE_IN_MAX_PLY = VALUE_MATE - MAX_PLY,
VALUE_MATED_IN_MAX_PLY = -VALUE_MATE_IN_MAX_PLY,
PawnValueMg = 126, PawnValueEg = 208,
KnightValueMg = 781, KnightValueEg = 854,
BishopValueMg = 825, BishopValueEg = 915,
RookValueMg = 1276, RookValueEg = 1380,
QueenValueMg = 2538, QueenValueEg = 2682,
MidgameLimit = 15258, EndgameLimit = 3915
};
enum PieceType {
NO_PIECE_TYPE, PAWN, KNIGHT, BISHOP, ROOK, QUEEN, KING,
ALL_PIECES = 0,
PIECE_TYPE_NB = 8
};
enum Piece {
NO_PIECE,
W_PAWN = PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
B_PAWN = PAWN + 8, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING,
PIECE_NB = 16
};
constexpr Value PieceValue[PHASE_NB][PIECE_NB] = {
{ VALUE_ZERO, PawnValueMg, KnightValueMg, BishopValueMg, RookValueMg, QueenValueMg, VALUE_ZERO, VALUE_ZERO,
VALUE_ZERO, PawnValueMg, KnightValueMg, BishopValueMg, RookValueMg, QueenValueMg, VALUE_ZERO, VALUE_ZERO },
{ VALUE_ZERO, PawnValueEg, KnightValueEg, BishopValueEg, RookValueEg, QueenValueEg, VALUE_ZERO, VALUE_ZERO,
VALUE_ZERO, PawnValueEg, KnightValueEg, BishopValueEg, RookValueEg, QueenValueEg, VALUE_ZERO, VALUE_ZERO }
};
typedef int Depth;
enum : int {
DEPTH_QS_CHECKS = 0,
DEPTH_QS_NO_CHECKS = -1,
DEPTH_QS_RECAPTURES = -5,
DEPTH_NONE = -6,
DEPTH_OFFSET = -7 // value used only for TT entry occupancy check
};
enum Square : int {
SQ_A1, SQ_B1, SQ_C1, SQ_D1, SQ_E1, SQ_F1, SQ_G1, SQ_H1,
SQ_A2, SQ_B2, SQ_C2, SQ_D2, SQ_E2, SQ_F2, SQ_G2, SQ_H2,
SQ_A3, SQ_B3, SQ_C3, SQ_D3, SQ_E3, SQ_F3, SQ_G3, SQ_H3,
SQ_A4, SQ_B4, SQ_C4, SQ_D4, SQ_E4, SQ_F4, SQ_G4, SQ_H4,
SQ_A5, SQ_B5, SQ_C5, SQ_D5, SQ_E5, SQ_F5, SQ_G5, SQ_H5,
SQ_A6, SQ_B6, SQ_C6, SQ_D6, SQ_E6, SQ_F6, SQ_G6, SQ_H6,
SQ_A7, SQ_B7, SQ_C7, SQ_D7, SQ_E7, SQ_F7, SQ_G7, SQ_H7,
SQ_A8, SQ_B8, SQ_C8, SQ_D8, SQ_E8, SQ_F8, SQ_G8, SQ_H8,
SQ_NONE,
SQUARE_ZERO = 0,
SQUARE_NB = 64
};
enum Direction : int {
NORTH = 8,
EAST = 1,
SOUTH = -NORTH,
WEST = -EAST,
NORTH_EAST = NORTH + EAST,
SOUTH_EAST = SOUTH + EAST,
SOUTH_WEST = SOUTH + WEST,
NORTH_WEST = NORTH + WEST
};
enum File : int {
FILE_A, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_H, FILE_NB
};
enum Rank : int {
RANK_1, RANK_2, RANK_3, RANK_4, RANK_5, RANK_6, RANK_7, RANK_8, RANK_NB
};
// Keep track of what a move changes on the board (used by NNUE)
struct DirtyPiece {
// Number of changed pieces
int dirty_num;
// Max 3 pieces can change in one move. A promotion with capture moves
// both the pawn and the captured piece to SQ_NONE and the piece promoted
// to from SQ_NONE to the capture square.
Piece piece[3];
// From and to squares, which may be SQ_NONE
Square from[3];
Square to[3];
};
/// Score enum stores a middlegame and an endgame value in a single integer (enum).
/// The least significant 16 bits are used to store the middlegame value and the
/// upper 16 bits are used to store the endgame value. We have to take care to
/// avoid left-shifting a signed int to avoid undefined behavior.
enum Score : int { SCORE_ZERO };
constexpr Score make_score(int mg, int eg) {
return Score((int)((unsigned int)eg << 16) + mg);
}
/// Extracting the signed lower and upper 16 bits is not so trivial because
/// according to the standard a simple cast to short is implementation defined
/// and so is a right shift of a signed integer.
inline Value eg_value(Score s) {
union { uint16_t u; int16_t s; } eg = { uint16_t(unsigned(s + 0x8000) >> 16) };
return Value(eg.s);
}
inline Value mg_value(Score s) {
union { uint16_t u; int16_t s; } mg = { uint16_t(unsigned(s)) };
return Value(mg.s);
}
#define ENABLE_BASE_OPERATORS_ON(T) \
constexpr T operator+(T d1, int d2) { return T(int(d1) + d2); } \
constexpr T operator-(T d1, int d2) { return T(int(d1) - d2); } \
constexpr T operator-(T d) { return T(-int(d)); } \
inline T& operator+=(T& d1, int d2) { return d1 = d1 + d2; } \
inline T& operator-=(T& d1, int d2) { return d1 = d1 - d2; }
#define ENABLE_INCR_OPERATORS_ON(T) \
inline T& operator++(T& d) { return d = T(int(d) + 1); } \
inline T& operator--(T& d) { return d = T(int(d) - 1); }
#define ENABLE_FULL_OPERATORS_ON(T) \
ENABLE_BASE_OPERATORS_ON(T) \
constexpr T operator*(int i, T d) { return T(i * int(d)); } \
constexpr T operator*(T d, int i) { return T(int(d) * i); } \
constexpr T operator/(T d, int i) { return T(int(d) / i); } \
constexpr int operator/(T d1, T d2) { return int(d1) / int(d2); } \
inline T& operator*=(T& d, int i) { return d = T(int(d) * i); } \
inline T& operator/=(T& d, int i) { return d = T(int(d) / i); }
ENABLE_FULL_OPERATORS_ON(Value)
ENABLE_FULL_OPERATORS_ON(Direction)
ENABLE_INCR_OPERATORS_ON(Piece)
ENABLE_INCR_OPERATORS_ON(PieceType)
ENABLE_INCR_OPERATORS_ON(Square)
ENABLE_INCR_OPERATORS_ON(File)
ENABLE_INCR_OPERATORS_ON(Rank)
ENABLE_BASE_OPERATORS_ON(Score)
#undef ENABLE_FULL_OPERATORS_ON
#undef ENABLE_INCR_OPERATORS_ON
#undef ENABLE_BASE_OPERATORS_ON
/// Additional operators to add a Direction to a Square
constexpr Square operator+(Square s, Direction d) { return Square(int(s) + int(d)); }
constexpr Square operator-(Square s, Direction d) { return Square(int(s) - int(d)); }
inline Square& operator+=(Square& s, Direction d) { return s = s + d; }
inline Square& operator-=(Square& s, Direction d) { return s = s - d; }
/// Only declared but not defined. We don't want to multiply two scores due to
/// a very high risk of overflow. So user should explicitly convert to integer.
Score operator*(Score, Score) = delete;
/// Division of a Score must be handled separately for each term
inline Score operator/(Score s, int i) {
return make_score(mg_value(s) / i, eg_value(s) / i);
}
/// Multiplication of a Score by an integer. We check for overflow in debug mode.
inline Score operator*(Score s, int i) {
Score result = Score(int(s) * i);
assert(eg_value(result) == (i * eg_value(s)));
assert(mg_value(result) == (i * mg_value(s)));
assert((i == 0) || (result / i) == s);
return result;
}
/// Multiplication of a Score by a boolean
inline Score operator*(Score s, bool b) {
return b ? s : SCORE_ZERO;
}
constexpr Color operator~(Color c) {
return Color(c ^ BLACK); // Toggle color
}
constexpr Square flip_rank(Square s) { // Swap A1 <-> A8
return Square(s ^ SQ_A8);
}
constexpr Square flip_file(Square s) { // Swap A1 <-> H1
return Square(s ^ SQ_H1);
}
constexpr Piece operator~(Piece pc) {
return Piece(pc ^ 8); // Swap color of piece B_KNIGHT <-> W_KNIGHT
}
constexpr CastlingRights operator&(Color c, CastlingRights cr) {
return CastlingRights((c == WHITE ? WHITE_CASTLING : BLACK_CASTLING) & cr);
}
constexpr Value mate_in(int ply) {
return VALUE_MATE - ply;
}
constexpr Value mated_in(int ply) {
return -VALUE_MATE + ply;
}
constexpr Square make_square(File f, Rank r) {
return Square((r << 3) + f);
}
constexpr Piece make_piece(Color c, PieceType pt) {
return Piece((c << 3) + pt);
}
constexpr PieceType type_of(Piece pc) {
return PieceType(pc & 7);
}
inline Color color_of(Piece pc) {
assert(pc != NO_PIECE);
return Color(pc >> 3);
}
constexpr bool is_ok(Square s) {
return s >= SQ_A1 && s <= SQ_H8;
}
constexpr File file_of(Square s) {
return File(s & 7);
}
constexpr Rank rank_of(Square s) {
return Rank(s >> 3);
}
constexpr Square relative_square(Color c, Square s) {
return Square(s ^ (c * 56));
}
constexpr Rank relative_rank(Color c, Rank r) {
return Rank(r ^ (c * 7));
}
constexpr Rank relative_rank(Color c, Square s) {
return relative_rank(c, rank_of(s));
}
constexpr Direction pawn_push(Color c) {
return c == WHITE ? NORTH : SOUTH;
}
constexpr Square from_sq(Move m) {
return Square((m >> 6) & 0x3F);
}
constexpr Square to_sq(Move m) {
return Square(m & 0x3F);
}
constexpr int from_to(Move m) {
return m & 0xFFF;
}
constexpr MoveType type_of(Move m) {
return MoveType(m & (3 << 14));
}
constexpr PieceType promotion_type(Move m) {
return PieceType(((m >> 12) & 3) + KNIGHT);
}
constexpr Move make_move(Square from, Square to) {
return Move((from << 6) + to);
}
constexpr Move reverse_move(Move m) {
return make_move(to_sq(m), from_sq(m));
}
template<MoveType T>
constexpr Move make(Square from, Square to, PieceType pt = KNIGHT) {
return Move(T + ((pt - KNIGHT) << 12) + (from << 6) + to);
}
constexpr bool is_ok(Move m) {
return from_sq(m) != to_sq(m); // Catch MOVE_NULL and MOVE_NONE
}
/// Based on a congruential pseudo random number generator
constexpr Key make_key(uint64_t seed) {
return seed * 6364136223846793005ULL + 1442695040888963407ULL;
}
} // namespace Stockfish
#endif // #ifndef TYPES_H_INCLUDED
#include "tune.h" // Global visibility to tuning setup