root.c File Reference

#include "search.h"
#include "bit.h"
#include "options.h"
#include "stats.h"
#include "util.h"
#include "ybwc.h"
#include "settings.h"
#include <stdlib.h>
#include <assert.h>

Functions
void	pv_debug (Search *search, const Move *bestmove, FILE *f)
	Debug PV. More...
bool	is_pv_ok (Search *search, int bestmove, int search_depth)
	Check if PV is ok. More...
static int	guess_move (Search *search, Board *board)
	Guess a move. More...
void	record_best_move (Search *search, const Board *init_board, const Move *bestmove, const int alpha, const int beta, const int depth)
	Record best move. More...
void	show_current_move (FILE *f, Search *search, const Move *move, const int alpha, const int beta, const bool parallel)
int	search_bound (const Search *search, int score)
	bound root scores according to stable squares More...
static int	search_route_PVS (Search *search, int alpha, int beta, const int depth, Node *node)
	Reroute the PVS between midgame,endgame or terminal PVS. More...
int	search_get_pv_cost (Search *search)
	Compute a cost as a combination of node count, depth, etc. from hash_table. More...
int	PVS_root (Search *search, const int alpha, const int beta, const int depth)
	Principal Variation Search algorithm at the root of the tree. More...
int	aspiration_search (Search *search, int alpha, int beta, const int depth, int score)
	Aspiration window. More...
static bool	get_last_level (Search *search, int *depth, int *selectivity)
	Retrieve the last level of the search. More...
void	iterative_deepening (Search *search, int alpha, int beta)
	Iterative deepening. More...
void *	search_run (void *v)
	Search the bestmove of a given board. More...

Variables
Log	search_log [1]
Log	engine_log [1]

Detailed Description

Search near the end of the game.

Date

1998 - 2017

Author

Richard Delorme

Version

4.4

Function Documentation

aspiration_search()

int aspiration_search	(	Search *	search,
		int	alpha,
		int	beta,
		const int	depth,
		int	score
	)

Aspiration window.

Parameters

search	Search.
alpha	Alpha bound.
beta	Beta bound.
depth	Depth.
score	Previous score.

Returns

A score.

get_last_level()

static bool get_last_level ( Search *  search, int *  depth, int *  selectivity  )

static

Retrieve the last level of the search.

Parameters

search	Search.
depth	Depth of the last search.
selectivity	Selectivity of the last search.

guess_move()

static int guess_move ( Search *  search, Board *  board  )

static

Guess a move.

this function is used when no move is found in the position retrieved from the hash table, meaning a fail-low search without a good move happened. A move is guessed after a "shallow search".

Parameters

search	Search.
board	Board to guess move from.

Returns

a best move guessed from a shallow search (depth = 4).

is_pv_ok()

bool is_pv_ok	(	Search *	search,
		int	bestmove,
		int	search_depth
	)

Check if PV is ok.

Parameters

search	Search.
bestmove	Best move.
search_depth	Depth.

Returns

true if PV is ok.

iterative_deepening()

void iterative_deepening	(	Search *	search,
		int	alpha,
		int	beta
	)

Iterative deepening.

Search the current position at increasing depths, and once full depth (equaling the number of empties) has been reached at decreasing selectivity ; until the position is eventually solved.

Parameters

search	Search.
alpha	Alpha bound.
beta	Beta bound.

pv_debug()

void pv_debug	(	Search *	search,
		const Move *	bestmove,
		FILE *	f
	)

Debug PV.

Parameters

search	Search.
bestmove	Best move.
f	Output stream.

PVS_root()

int PVS_root	(	Search *	search,
		const int	alpha,
		const int	beta,
		const int	depth
	)

Principal Variation Search algorithm at the root of the tree.

this function solves the position provided within the limits set by the alpha and beta bounds. The movelist parameter is updated so that the bestmove is the first of the list when the search ended.

Parameters

search	Search.
alpha	Alpha bound.
beta	Beta bound.
depth	Remaining depth.

Returns

A score, as a disc difference.

record_best_move()

void record_best_move	(	Search *	search,
		const Board *	init_board,
		const Move *	bestmove,
		const int	alpha,
		const int	beta,
		const int	depth
	)

Record best move.

Parameters

search	Search.
init_board	Initial board.
bestmove	Best move.
alpha	Alpha Bound.
beta	Beta Bound.
depth	Depth.

search_bound()

int search_bound	(	const Search *	search,
		int	score
	)

bound root scores according to stable squares

Parameters

search	Position to search.
score	score to bound.

Returns

score;

search_get_pv_cost()

int search_get_pv_cost

(

Search *

search

)

Compute a cost as a combination of node count, depth, etc. from hash_table.

The board is supposed to be updated by a move after the root position.

Parameters

search

Search.

Returns

A search cost.

search_route_PVS()

static int search_route_PVS ( Search *  search, int  alpha, int  beta, const int  depth, Node *  node  )

static

Reroute the PVS between midgame,endgame or terminal PVS.

Parameters

search	Search.
alpha	Alpha bound.
beta	Beta bound.
depth	Depth.
node	Node position.

Returns

A score, as a disc difference.

search_run()

void * search_run

(

void *

v

)

Search the bestmove of a given board.

this is a function runable within its own thread. The board is supposed to have been set (by search_set_board()), and all search options (level, time, etc.) too. this function proceeds to some internal initialisations and then call the iterative deepening function, from where the search is actually done. After the search ends, some finalizations are done before the function returns.

Parameters

v	Search cast as void.

Returns

The search result.

show_current_move()

void show_current_move	(	FILE *	f,
		Search *	search,
		const Move *	move,
		const int	alpha,
		const int	beta,
		const bool	parallel
	)

Variable Documentation

engine_log

Log engine_log[1]

extern

search_log

Log search_log[1]

extern