MCTS Class Reference

Monte Carlo Tree Search engine. More...

#include <MCTS.h>

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Public Member Functions
	MCTS (IEvaluator &eval)
Move	startSearch (Board &root, const SearchParams &params) override
	Starts the search process on the given root board.
void	stop () override
	Asynchronously signals the search to stop immediately.
bool	isSearching () const override
	Checks if the search algorithm is currently running.
void	setInfoCallback (InfoCallback callback) override
	Sets the callback function for periodic information updates.
uint64_t	getNodes () const override
	Retrieves the total number of nodes evaluated by the search algorithm.
void	setExplorationConstant (float c)
	Sets the exploration constant (Cp) used in the UCB calculation.
Public Member Functions inherited from ISearch
virtual	~ISearch ()=default

Private Member Functions
MCTSNode *	selection (MCTSNode *node, Board &board)
void	expansion (MCTSNode *node, Board &board)
float	simulation (Board &board)
void	backpropagation (MCTSNode *node, float value)
MCTSNode *	selectBestChild (MCTSNode *node) const
MCTSNode *	selectUCBChild (MCTSNode *node) const

Private Attributes
IEvaluator &	evalCtx_
	The evaluator used for leaf node evaluation.
std::unique_ptr< MCTSNode >	root_
	Root node of the search tree.
std::atomic< bool >	stopFlag_ {false}
	Signals the search to stop.
std::atomic< bool >	searching_ {false}
	True while a search is active.
std::atomic< uint64_t >	nodes_ {0}
	Total nodes visited.
float	explorationConstant_ = 1.41f
	Weight of exploration in UCB formula.
int	maxPlayouts_ = 100000
	Hard limit on search iterations.
InfoCallback	infoCallback_
	Callback for UCI info updates.

Detailed Description

Monte Carlo Tree Search engine.

Implements the ISearch interface. Explores the game tree asymmetrically by repeatedly selecting, expanding, simulating, and backpropagating.

Constructor & Destructor Documentation

MCTS()

MCTS::MCTS

(

IEvaluator &

eval

)

Member Function Documentation

backpropagation()

void MCTS::backpropagation ( MCTSNode * node, float value )

private

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expansion()

void MCTS::expansion ( MCTSNode * node, Board & board )

private

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getNodes()

uint64_t MCTS::getNodes ( ) const

inlineoverridevirtual

Retrieves the total number of nodes evaluated by the search algorithm.

Returns

The node count.

Implements ISearch.

isSearching()

bool MCTS::isSearching ( ) const

inlineoverridevirtual

Checks if the search algorithm is currently running.

Returns

True if a search is in progress.

Implements ISearch.

selectBestChild()

MCTSNode * MCTS::selectBestChild ( MCTSNode * node ) const

private

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selection()

MCTSNode * MCTS::selection ( MCTSNode * node, Board & board )

private

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selectUCBChild()

MCTSNode * MCTS::selectUCBChild ( MCTSNode * node ) const

private

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setExplorationConstant()

void MCTS::setExplorationConstant ( float c )

inline

Sets the exploration constant (Cp) used in the UCB calculation.

setInfoCallback()

void MCTS::setInfoCallback ( InfoCallback callback )

inlineoverridevirtual

Sets the callback function for periodic information updates.

Parameters

callback

The function to call with depth, score, node count, NPS, and PV.

Implements ISearch.

simulation()

float MCTS::simulation ( Board & board )

private

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startSearch()

Move MCTS::startSearch ( Board & root, const SearchParams & params )

overridevirtual

Starts the search process on the given root board.

This is a blocking call that will execute the search algorithm until the stopping conditions in params (or stop()) are met.

Parameters

root	The starting board position.
params	The time and depth constraints for the search.

Returns

The best move found.

Implements ISearch.

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stop()

void MCTS::stop ( )

inlineoverridevirtual

Asynchronously signals the search to stop immediately.

This method must be thread-safe.

Implements ISearch.

Member Data Documentation

evalCtx_

IEvaluator& MCTS::evalCtx_

private

The evaluator used for leaf node evaluation.

explorationConstant_

float MCTS::explorationConstant_ = 1.41f

private

Weight of exploration in UCB formula.

infoCallback_

InfoCallback MCTS::infoCallback_

private

Callback for UCI info updates.

maxPlayouts_

int MCTS::maxPlayouts_ = 100000

private

Hard limit on search iterations.

nodes_

std::atomic<uint64_t> MCTS::nodes_ {0}

private

Total nodes visited.

root_

std::unique_ptr<MCTSNode> MCTS::root_

private

Root node of the search tree.

searching_

std::atomic<bool> MCTS::searching_ {false}

private

True while a search is active.

stopFlag_

std::atomic<bool> MCTS::stopFlag_ {false}

private

Signals the search to stop.

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

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