TwoDistance Class Reference

TwoDistance Evaluation Function. More...

#include <TwoDistance.hpp>

Public Types
enum	NeighbourType { ADJACENT, FULL_VC }
	Two types of cell neighbourhoods: ADJACENT and FULL_VC. More...
Public Member Functions
	TwoDistance (NeighbourType ntype=ADJACENT)
	Compute the TwoDistance on the given HexBoard (with up-to-date VCs) and NeighbourType.
virtual	~TwoDistance ()
	Destructor.
virtual void	Evaluate (const HexBoard &brd)
	Computes the evaluation.
virtual HexEval	Score () const
	Returns the computed score for BLACK, that is:
virtual HexEval	Score (HexPoint cell) const
	Returns the sum of the BLACK and WHITE scores for this cell.
virtual HexEval	Score (HexPoint cell, HexColor color) const
	Returns the score for cell and color.
Private Member Functions
void	ComputeScores (HexColor color, HexEval *out)
void	FindBest (HexEval *po, HexPoint &who, int &count)
void	ComputeScore ()
void	ComputeDistanceToEdge (HexColor color, HexPoint edge1, HexEval *out)
bool	IsAdjacent (HexColor color, HexPoint p1, HexPoint p2)
void	SetAllToInfinity (HexEval *out)
Private Attributes
const HexBoard *	m_brd
NeighbourType	m_ntype
HexEval	m_score
HexEval	m_scores [BLACK_AND_WHITE][BITSETSIZE]

Detailed Description

TwoDistance Evaluation Function.

Computes the two distance from each cell to each of the four edges. The two distance is the second shortest distance between two cells (1 if they are adjacent, and infinity if fewer than two connecting paths exist).

This evaluation function requires that the VCs be precalculated for the given board state. This calcuation runs in O(n^2) time, where n is the number of cells on the board.

Bug:: if NeighbourType is FULL_VC then the distance returned is not accurate since one cell we have a vc with could affect another cell we have a vc with.

Definition at line 32 of file TwoDistance.hpp.

Member Enumeration Documentation

enum TwoDistance::NeighbourType

Two types of cell neighbourhoods: ADJACENT and FULL_VC.

ADJACENT: standard adjacency, going through stones of like color. FULL_VC: two cells are adjacent if a FULL vc exists between them.

Enumerator:

ADJACENT
FULL_VC

Definition at line 41 of file TwoDistance.hpp.

Constructor & Destructor Documentation

TwoDistance::TwoDistance ( NeighbourType ntype = ADJACENT ) [explicit]

Compute the TwoDistance on the given HexBoard (with up-to-date VCs) and NeighbourType.

Definition at line 15 of file TwoDistance.cpp.

TwoDistance::~TwoDistance ( ) [virtual]

Destructor.

Definition at line 22 of file TwoDistance.cpp.

Member Function Documentation

void TwoDistance::ComputeDistanceToEdge	(	HexColor	color,
		HexPoint	edge1,
		HexEval *	out
	)			`[private]`

Definition at line 100 of file TwoDistance.cpp.

References StoneBoard::GetEmpty(), HexBoard::GetPosition(), IsAdjacent(), m_brd, and SetAllToInfinity().

Referenced by ComputeScores().

void TwoDistance::ComputeScore ( ) [private]

Definition at line 74 of file TwoDistance.cpp.

References BLACK, FindBest(), m_score, m_scores, and WHITE.

Referenced by Evaluate().

void TwoDistance::ComputeScores	(	HexColor	color,
		HexEval *	out
	)			`[private]`

Definition at line 36 of file TwoDistance.cpp.

References TwoDistUtil::AddDistance(), BITSETSIZE, HexPointUtil::colorEdge1(), HexPointUtil::colorEdge2(), ComputeDistanceToEdge(), HexBoard::Const(), HexBoard::GetPosition(), HexEval, ConstBoard::Interior(), StoneBoard::IsOccupied(), and m_brd.

Referenced by Evaluate().

void TwoDistance::Evaluate ( const HexBoard & brd ) [virtual]

Computes the evaluation.

Definition at line 28 of file TwoDistance.cpp.

References ComputeScore(), ComputeScores(), m_brd, and m_scores.

Referenced by BenzeneHtpEngine::CmdEvalTwoDist().

void TwoDistance::FindBest	(	HexEval *	po,
		HexPoint &	who,
		int &	count
	)			`[private]`

Definition at line 52 of file TwoDistance.cpp.

References EVAL_INFINITY, StoneBoard::GetEmpty(), HexBoard::GetPosition(), HexAssert, HexEval, INVALID_POINT, and m_brd.

Referenced by ComputeScore().

bool TwoDistance::IsAdjacent	(	HexColor	color,
		HexPoint	p1,
		HexPoint	p2
	)			`[private]`

Definition at line 88 of file TwoDistance.cpp.

References ADJACENT, HexBoard::Cons(), VC::FULL, FULL_VC, VC::IsEmpty(), m_brd, m_ntype, and VCSet::SmallestVC().

Referenced by ComputeDistanceToEdge().

HexEval TwoDistance::Score	(	HexPoint	cell,
		HexColor	color
	)			const `[inline, virtual]`

Returns the score for cell and color.

This is the sum of the twodistances between both edges for cell.

Definition at line 102 of file TwoDistance.hpp.

References m_scores.

HexEval TwoDistance::Score ( HexPoint cell ) const [inline, virtual]

Returns the sum of the BLACK and WHITE scores for this cell.

Definition at line 108 of file TwoDistance.hpp.

References BLACK, m_scores, and WHITE.

HexEval TwoDistance::Score ( ) const [inline, virtual]

Returns the computed score for BLACK, that is:

Score = SCALE*(B_m - W_m) + (B_mc - W_mc);

Where SCALE is an arbitrary scaling factor (hex setting "twod-scale-factor"), B_m and W_m are the minimum BLACK and WHITE cell scores, and B_mc and W_mc are equal to the number of times B_m and W_m appear on the board.

B_mc and W_mc are tie breaking values. The intuition here is that a position with many cells with minimum potential is better than a position with only a single cell with minimum potential.

Definition at line 97 of file TwoDistance.hpp.

References m_score.

Referenced by BenzeneHtpEngine::CmdEvalTwoDist().

void TwoDistance::SetAllToInfinity ( HexEval * out ) [private]

Definition at line 160 of file TwoDistance.cpp.

References HexBoard::Const(), EVAL_INFINITY, ConstBoard::Interior(), and m_brd.

Referenced by ComputeDistanceToEdge().