Package elki.database.query.distance

Class LinearScanPrioritySearcher<Q,O>

java.lang.Object

elki.database.query.distance.LinearScanPrioritySearcher<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:

LinearScanPrioritySearcher.ByDBID, LinearScanPrioritySearcher.ByObject

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

Default linear scan search class.

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	LinearScanPrioritySearcher.ByDBID<O>	Search by DBID.
static class	LinearScanPrioritySearcher.ByObject<O>	Search by Object.

Field Summary

Fields

Modifier and Type	Field	Description
protected double	curdist	Current distance
protected DistanceQuery<O>	distanceQuery	Distance to use.
protected DBIDIter	iter	Iterator.
protected O	query	Current query object.

Constructor Summary

Constructors

Constructor	Description
LinearScanPrioritySearcher(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	getUpperBound()	Get the upper bound (if available).
int	internalGetIndex()	Internal only: Get the internal index.
protected PrioritySearcher<Q>	realSearch(O query)	Implementation of the 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> distanceQuery

Distance to use.

iter

protected DBIDIter iter

Iterator.

query

protected O query

Current query object.

curdist

protected double curdist

Current distance

Constructor Detail

LinearScanPrioritySearcher

public LinearScanPrioritySearcher(DistanceQuery<O> distanceQuery)

Constructor.

Parameters:

distanceQuery - Distance function to use

Method Detail

realSearch

protected PrioritySearcher<Q> realSearch(O query)

Implementation of the 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

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)