TranspositionTable Class Reference

The main Transposition Table. More...

#include <TT.h>

Collaboration diagram for TranspositionTable:

Public Member Functions
	TranspositionTable ()=default
	~TranspositionTable ()
void	resize (size_t mb)
	Resizes the Transposition Table to the specified capacity in Megabytes.
void	clear ()
	Clears the contents of the Transposition Table.
void	newSearch ()
	Increments the internal age generation to age out older entries.
void	setDisabled (bool disabled)
void	setNumThreads (int n)
int	hashfull () const
	Calculates the utilization of the Transposition Table (per-mille).
void	prefetch (uint64_t key) const
	Issues a memory prefetch instruction for the cluster corresponding to the key.
bool	probe (uint64_t key, int depth, int &score, Move &bestMove, int &entryDepth, Bound &entryBound) const
	Fully probes the TT for a search entry matching the key.
Move	probeMove (uint64_t key) const
	Lightly probes the TT just to extract the best move (for move ordering).
std::optional< int >	probeScore (uint64_t key) const
	Lightly probes the TT to extract only the score (for pruning heuristics).
bool	probeEval (uint64_t key, int16_t &score) const
	Probes the dedicated static evaluation slot.
void	storeEval (uint64_t key, int16_t score)
	Stores a static evaluation in the dedicated slot.
void	store (uint64_t key, int depth, int score, Bound bound, Move bestMove, int staticEval=0)
	Stores search results into the best slot in the cluster.
void	dumpToFile (const std::string &filename) const
bool	saveFullToFile (const std::string &filename) const
bool	loadFullFromFile (const std::string &filename)

Private Member Functions
size_t	index (uint64_t key) const
int	ageDiff (uint8_t entryAge) const

Private Attributes
Cluster *	table_ = nullptr
	Pointer to the heap-allocated clusters.
size_t	clusterCount_ = 0
	Number of available clusters.
size_t	indexMask_ = 0
	Bitmask for fast modulo addressing.
uint8_t	currentAge_ = 0
	Current generation age (used to age out old entries).
bool	disableTT_ = false
	Flag to disable the TT entirely.
int	numThreads_ = 1
	Number of threads sharing the table.
bool	usingHugePages_ = false
	True if the memory was allocated via HugePages.

Detailed Description

The main Transposition Table.

Manages allocation, probing, and replacement of clusters using a lockless architecture suitable for SMP search.

Constructor & Destructor Documentation

TranspositionTable()

TranspositionTable::TranspositionTable ( )

default

~TranspositionTable()

TranspositionTable::~TranspositionTable

(

)

Member Function Documentation

ageDiff()

int TranspositionTable::ageDiff ( uint8_t entryAge ) const

inlineprivate

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clear()

void TranspositionTable::clear

(

)

Clears the contents of the Transposition Table.

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dumpToFile()

void TranspositionTable::dumpToFile

(

const std::string &

filename

)

const

hashfull()

int TranspositionTable::hashfull

(

)

const

Calculates the utilization of the Transposition Table (per-mille).

index()

size_t TranspositionTable::index ( uint64_t key ) const

inlineprivate

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loadFullFromFile()

bool TranspositionTable::loadFullFromFile

(

const std::string &

filename

)

newSearch()

void TranspositionTable::newSearch ( )

inline

Increments the internal age generation to age out older entries.

prefetch()

void TranspositionTable::prefetch

(

uint64_t

key

)

const

Issues a memory prefetch instruction for the cluster corresponding to the key.

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probe()

bool TranspositionTable::probe	(	uint64_t	key,
		int	depth,
		int &	score,
		Move &	bestMove,
		int &	entryDepth,
		Bound &	entryBound ) const

Fully probes the TT for a search entry matching the key.

Returns

True if a valid entry was found and the output parameters populated.

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probeEval()

bool TranspositionTable::probeEval	(	uint64_t	key,
		int16_t &	score ) const

Probes the dedicated static evaluation slot.

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probeMove()

Move TranspositionTable::probeMove

(

uint64_t

key

)

const

Lightly probes the TT just to extract the best move (for move ordering).

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probeScore()

std::optional< int > TranspositionTable::probeScore

(

uint64_t

key

)

const

Lightly probes the TT to extract only the score (for pruning heuristics).

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resize()

void TranspositionTable::resize

(

size_t

mb

)

Resizes the Transposition Table to the specified capacity in Megabytes.

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saveFullToFile()

bool TranspositionTable::saveFullToFile

(

const std::string &

filename

)

const

setDisabled()

void TranspositionTable::setDisabled ( bool disabled )

inline

setNumThreads()

void TranspositionTable::setNumThreads ( int n )

inline

store()

void TranspositionTable::store	(	uint64_t	key,
		int	depth,
		int	score,
		Bound	bound,
		Move	bestMove,
		int	staticEval = 0 )

Stores search results into the best slot in the cluster.

Implements a replacement scheme based on depth and age.

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storeEval()

void TranspositionTable::storeEval	(	uint64_t	key,
		int16_t	score )

Stores a static evaluation in the dedicated slot.

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Member Data Documentation

clusterCount_

size_t TranspositionTable::clusterCount_ = 0

private

Number of available clusters.

currentAge_

uint8_t TranspositionTable::currentAge_ = 0

private

Current generation age (used to age out old entries).

disableTT_

bool TranspositionTable::disableTT_ = false

private

Flag to disable the TT entirely.

indexMask_

size_t TranspositionTable::indexMask_ = 0

private

Bitmask for fast modulo addressing.

numThreads_

int TranspositionTable::numThreads_ = 1

private

Number of threads sharing the table.

table_

Cluster* TranspositionTable::table_ = nullptr

private

Pointer to the heap-allocated clusters.

usingHugePages_

bool TranspositionTable::usingHugePages_ = false

private

True if the memory was allocated via HugePages.

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The documentation for this class was generated from the following files:

• engine/src/search/TT.h
• engine/src/search/TT.cpp