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perf: remove second hash history keeping #355

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Aug 8, 2023
Merged

perf: remove second hash history keeping #355

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21 changes: 7 additions & 14 deletions src/board.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@

Board::Board(const std::string &fen) {
state_history_.reserve(MAX_PLY);
hash_history_.reserve(512);

side_to_move_ = WHITE;
en_passant_square_ = NO_SQ;
Expand All @@ -27,8 +26,6 @@ Board::Board(const Board &other) {

state_history_ = other.state_history_;

hash_history_ = other.hash_history_;

pieces_bb_ = other.pieces_bb_;
board_ = other.board_;

Expand Down Expand Up @@ -58,8 +55,6 @@ Board &Board::operator=(const Board &other) {

state_history_ = other.state_history_;

hash_history_ = other.hash_history_;

pieces_bb_ = other.pieces_bb_;
board_ = other.board_;

Expand Down Expand Up @@ -188,7 +183,6 @@ void Board::setFen(const std::string &fen, bool update_acc) {
}

state_history_.clear();
hash_history_.clear();
accumulators_->clear();

hash_key_ = zobrist();
Expand Down Expand Up @@ -261,9 +255,9 @@ std::string Board::getFen() const {
bool Board::isRepetition(int draw) const {
uint8_t c = 0;

for (int i = static_cast<int>(hash_history_.size()) - 2;
i >= 0 && i >= static_cast<int>(hash_history_.size()) - half_move_clock_ - 1; i -= 2) {
if (hash_history_[i] == hash_key_) c++;
for (int i = static_cast<int>(state_history_.size()) - 2;
i >= 0 && i >= static_cast<int>(state_history_.size()) - half_move_clock_ - 1; i -= 2) {
if (state_history_[i].hash == hash_key_) c++;
if (c == draw) return true;
}

Expand Down Expand Up @@ -326,8 +320,8 @@ bool Board::isAttacked(Color c, Square sq, Bitboard occ) const {
}

void Board::makeNullMove() {
state_history_.emplace_back(en_passant_square_, castling_rights_, half_move_clock_, NONE);

state_history_.emplace_back(hash_key_, castling_rights_, en_passant_square_, half_move_clock_,
NONE);
// Update the hash key
hash_key_ ^= zobrist::sideToMove();
if (en_passant_square_ != NO_SQ)
Expand All @@ -345,15 +339,14 @@ void Board::unmakeNullMove() {
const State restore = state_history_.back();
state_history_.pop_back();

en_passant_square_ = restore.en_passant;
en_passant_square_ = restore.enpassant;

hash_key_ ^= zobrist::sideToMove();
if (en_passant_square_ != NO_SQ)
hash_key_ ^= zobrist::enpassant(squareFile(en_passant_square_));

castling_rights_ = restore.castling;
half_move_clock_ = restore.half_move;

half_move_clock_ = restore.half_moves;
full_move_number_--;
side_to_move_ = ~side_to_move_;
}
Expand Down
40 changes: 22 additions & 18 deletions src/board.h
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Original file line number Diff line number Diff line change
Expand Up @@ -22,7 +22,6 @@
#include "types.h"
#include "zobrist.h"


extern TranspositionTable TTable;

class Board {
Expand Down Expand Up @@ -89,6 +88,14 @@ class Board {

[[nodiscard]] Bitboard all() const;

/// @brief Returns the square of the king for a certain color
/// @param color
/// @return
[[nodiscard]] Square kingSq(Color color) const {
assert(pieces(PieceType::KING, color) != 0);
return builtin::lsb(pieces(PieceType::KING, color));
}

// Gets individual piece bitboards

[[nodiscard]] constexpr Bitboard pieces(Piece piece) const { return pieces_bb_[piece]; }
Expand All @@ -111,6 +118,11 @@ class Board {
/// @return
[[nodiscard]] Color colorOf(Square loc) const;

/// @brief Checks if a square is attacked by the given color.
/// @param c
/// @param sq
/// @param occ
/// @return
[[nodiscard]] bool isAttacked(Color c, Square sq, Bitboard occ) const;

void updateHash(Move move);
Expand Down Expand Up @@ -141,8 +153,6 @@ class Board {

void clearStacks();

void clearHash() { hash_history_.clear(); }

friend std::ostream &operator<<(std::ostream &os, const Board &b);

bool chess960 = false;
Expand All @@ -152,10 +162,6 @@ class Board {

std::vector<State> state_history_;

// keeps track of previous hashes, used for
// repetition detection
std::vector<U64> hash_history_;

std::array<Bitboard, 12> pieces_bb_ = {};
std::array<Piece, MAX_SQ> board_{};

Expand Down Expand Up @@ -230,10 +236,10 @@ inline void Board::updateHash(Move move) {
const Piece capture = board_[to_sq];
const Rank rank = squareRank(to_sq);

hash_history_.emplace_back(hash_key_);

if (en_passant_square_ != NO_SQ)
if (en_passant_square_ != NO_SQ) {
hash_key_ ^= zobrist::enpassant(squareFile(en_passant_square_));
}

en_passant_square_ = NO_SQ;

hash_key_ ^= zobrist::castling(castling_rights_.getHashIndex());
Expand Down Expand Up @@ -342,7 +348,8 @@ void Board::makeMove(const Move move) {
// STORE STATE HISTORY
// *****************************

state_history_.emplace_back(en_passant_square_, castling_rights_, half_move_clock_, capture);
state_history_.emplace_back(hash_key_, castling_rights_, en_passant_square_, half_move_clock_,
capture);

if constexpr (updateNNUE) accumulators_->push();

Expand Down Expand Up @@ -418,7 +425,6 @@ void Board::makeMove(const Move move) {
template <bool updateNNUE>
void Board::unmakeMove(Move move) {
const State restore = state_history_.back();

const Square from_sq = from(move);
const Square to_sq = to(move);

Expand All @@ -433,15 +439,13 @@ void Board::unmakeMove(Move move) {
accumulators_->pop();
}

hash_key_ = hash_history_.back();
hash_key_ = restore.hash;
en_passant_square_ = restore.enpassant;
castling_rights_ = restore.castling;
half_move_clock_ = restore.half_moves;

hash_history_.pop_back();
state_history_.pop_back();

en_passant_square_ = restore.en_passant;
castling_rights_ = restore.castling;
half_move_clock_ = restore.half_move;

full_move_number_--;
side_to_move_ = ~side_to_move_;

Expand Down
2 changes: 0 additions & 2 deletions src/datagen.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@
#include "rand.h"
#include "syzygy/Fathom/src/tbprobe.h"


namespace datagen {

std::string stringFenData(const fenData &fen_data, double score) {
Expand Down Expand Up @@ -121,7 +120,6 @@ void TrainingData::randomPlayout(std::ofstream &file, Board &board, Movelist &mo
}

board.refreshNNUE(board.getAccumulator());
board.clearHash();
search->board = board;

fenData sfens;
Expand Down
17 changes: 10 additions & 7 deletions src/types/state.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4,14 +4,17 @@
#include "castling_rights.h"

struct State {
Square en_passant{};
CastlingRights castling{};
uint8_t half_move{};
Piece captured_piece = NONE;
U64 hash;
CastlingRights castling;
Square enpassant;
uint8_t half_moves;
Piece captured_piece;

State(Square en_passant, CastlingRights castling, uint8_t half_move, Piece captured_piece)
: en_passant(en_passant),
State(const U64 &hash, const CastlingRights &castling, const Square &enpassant,
const uint8_t &half_moves, const Piece &captured_piece)
: hash(hash),
castling(castling),
half_move(half_move),
enpassant(enpassant),
half_moves(half_moves),
captured_piece(captured_piece) {}
};