Package elki.database.query.distance

Class LinearScanEuclideanPrioritySearcher<Q,O extends NumberVector>

java.lang.Object

elki.database.query.distance.LinearScanEuclideanPrioritySearcher<Q,O>

Type Parameters:

Q - Query type

O - Relation object type

All Implemented Interfaces:

DBIDIter, DBIDRef, KNNSearcher<Q>, LinearScanQuery, PrioritySearcher<Q>, RangeSearcher<Q>, Iter

Direct Known Subclasses:

LinearScanEuclideanPrioritySearcher.ByDBID, LinearScanEuclideanPrioritySearcher.ByObject

public abstract class LinearScanEuclideanPrioritySearcher<Q,O extends NumberVector>
extends java.lang.Object
implements PrioritySearcher<Q>, LinearScanQuery

Default linear scan search class, for Euclidean distance.

This is a fallback option - results are not returned in order, and (as always) may exceed the given cutoff threshold.

Since:

0.4.0

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LinearScanEuclideanPrioritySearcher.ByDBID<O extends NumberVector>	Search by DBID.
static class	LinearScanEuclideanPrioritySearcher.ByObject<O extends NumberVector>	Search by Object.

Field Summary

Fields

Modifier and Type	Field	Description
private double	curdist	Current distance.
private double	curdistsq	Current squared distance.
protected DistanceQuery<O>	distanceQuery	Distance to use.
private DBIDIter	iter	Iterator.
private O	query	Current query object.
private static SquaredEuclideanDistance	SQUARED	Squared distance
private double	thresholdsq	Cutoff threshold.
private double	thresholdUp	Fake lower bound to return for cut-off values.

Constructor Summary

Constructors

Constructor	Description
LinearScanEuclideanPrioritySearcher(DistanceQuery<O> distanceQuery)	Constructor.

Method Summary

Modifier and Type	Method	Description
PrioritySearcher<Q>	advance()	Moves the iterator forward to the next entry.
double	allLowerBound()	Lower bound for all subsequent instances (that have been completely explored).
double	computeExactDistance()	Compute the exact distance to the current candidate.
PrioritySearcher<Q>	decreaseCutoff(double threshold)	Decrease the cutoff threshold.
double	getApproximateAccuracy()	Get approximate distance accuracy (if available).
double	getApproximateDistance()	Get approximate distance (if available).
double	getLowerBound()	Get the lower bound (if available).
double	getSquaredDistance()	Get the squared distance.
double	getUpperBound()	Get the upper bound (if available).
int	internalGetIndex()	Internal only: Get the internal index.
PrioritySearcher<Q>	realSearch(O query)	The real search function.
boolean	valid()	Returns true if the iterator currently points to a valid object.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface elki.database.ids.DBIDIter

addTo

Methods inherited from interface elki.database.ids.DBIDRef

equals, hashCode

Methods inherited from interface elki.database.query.PrioritySearcher

getKNN, getRange, search, search

Methods inherited from interface elki.database.query.range.RangeSearcher

getRange

Field Detail

distanceQuery

protected DistanceQuery<O extends NumberVector> distanceQuery

Distance to use.

iter

private DBIDIter iter

Iterator.

query

private O extends NumberVector query

Current query object.

thresholdUp

private double thresholdUp

Fake lower bound to return for cut-off values.

thresholdsq

private double thresholdsq

Cutoff threshold.

curdist

private double curdist

Current distance.

curdistsq

private double curdistsq

Current squared distance.

SQUARED

private static final SquaredEuclideanDistance SQUARED

Squared distance

Constructor Detail

LinearScanEuclideanPrioritySearcher

public LinearScanEuclideanPrioritySearcher(DistanceQuery<O> distanceQuery)

Constructor.

Parameters:

distanceQuery - Distance function to use

Method Detail

realSearch

public PrioritySearcher<Q> realSearch(O query)

The real search function.

Parameters:

query - Query object

Returns:

this

valid

public boolean valid()

Description copied from interface: Iter

Returns true if the iterator currently points to a valid object.

Specified by:

valid in interface Iter

Returns:

a boolean value, whether the position is valid.

advance

public PrioritySearcher<Q> advance()

Description copied from interface: Iter

Moves the iterator forward to the next entry.

Specified by:

advance in interface DBIDIter

Specified by:

advance in interface Iter

Specified by:

advance in interface PrioritySearcher<Q>

Returns:

The iterator itself.

internalGetIndex

public int internalGetIndex()

Description copied from interface: DBIDRef

Internal only: Get the internal index.

NOT FOR PUBLIC USE - ELKI Optimization engine only.

Specified by:

internalGetIndex in interface DBIDRef

Returns:

Internal index

decreaseCutoff

public PrioritySearcher<Q> decreaseCutoff(double threshold)

Description copied from interface: PrioritySearcher

Decrease the cutoff threshold.

The cutoff must not be increased, as the search may have pruned some results automatically.

Specified by:

decreaseCutoff in interface PrioritySearcher<Q>

Parameters:

threshold - Threshold parameter

Returns:

this, for chaining

computeExactDistance

public double computeExactDistance()

Description copied from interface: PrioritySearcher

Compute the exact distance to the current candidate.

The searcher may or may not have this value already.

Specified by:

computeExactDistance in interface PrioritySearcher<Q>

Returns:

Distance

getSquaredDistance

public double getSquaredDistance()

Get the squared distance.

Returns:

squared distance

getApproximateAccuracy

public double getApproximateAccuracy()

Description copied from interface: PrioritySearcher

Get approximate distance accuracy (if available).

Quality guarantees may vary a lot!

Specified by:

getApproximateAccuracy in interface PrioritySearcher<Q>

Returns:

Double.NaN if not valid

getApproximateDistance

public double getApproximateDistance()

Description copied from interface: PrioritySearcher

Get approximate distance (if available).

Quality guarantees may vary a lot!

Specified by:

getApproximateDistance in interface PrioritySearcher<Q>

Returns:

Double.NaN if not valid

getLowerBound

public double getLowerBound()

Description copied from interface: PrioritySearcher

Get the lower bound (if available).

Note: the lower bound is already checked by the cutoff of the priority search, so this is primarily useful for analyzing the search behavior.

Specified by:

getLowerBound in interface PrioritySearcher<Q>

Returns:

Double.NaN if not valid

getUpperBound

public double getUpperBound()

Description copied from interface: PrioritySearcher

Get the upper bound (if available).

Specified by:

getUpperBound in interface PrioritySearcher<Q>

Returns:

Double.NaN if not valid

allLowerBound

public double allLowerBound()

Description copied from interface: PrioritySearcher

Lower bound for all subsequent instances (that have been completely explored). The searcher guarantees that no further results will be returned with a distance less than this.

Specified by:

allLowerBound in interface PrioritySearcher<Q>

Returns:

lower bound; 0 if no guarantees (e.g., linear scan)