Package elki.distance

Class RandomStableDistance

java.lang.Object

elki.distance.AbstractDatabaseDistance<DBID>

elki.distance.RandomStableDistance

All Implemented Interfaces:

DBIDDistance, Distance<DBID>

@Priority(-100)
public class RandomStableDistance
extends AbstractDatabaseDistance<DBID>
implements DBIDDistance

This is a dummy distance providing random values (obviously not metrical), useful mostly for unit tests and baseline evaluations: obviously this distance provides no benefit whatsoever. This distance is based on the combined hash codes of the two objects queried, if they are different. Extra caution is done to ensure symmetry and objects with the same ID will have a distance of 0. Obviously this distance is not metrical.

Since:

0.4.0

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	RandomStableDistance.Par	Parameterization class.

Nested classes/interfaces inherited from class elki.distance.AbstractDatabaseDistance

AbstractDatabaseDistance.Instance<O>

Field Summary

Fields

Modifier and Type	Field	Description
private long	seed	Seed for reproducible random.
static RandomStableDistance	STATIC	Static instance

Constructor Summary

Constructors

Constructor	Description
RandomStableDistance(long seed)	Constructor.

Method Summary

Modifier and Type	Method	Description
double	distance(DBIDRef o1, DBIDRef o2)	Returns the distance between the two objects specified by their object ids.
boolean	equals(java.lang.Object obj)
TypeInformation	getInputTypeRestriction()	Get the input data type of the function.
int	hashCode()
<T extends DBID> DistanceQuery<T>	instantiate(Relation<T> relation)	Instantiate with a database to get the actual distance query.
private double	pseudoRandom(long seed, int input)	Pseudo random number generator, adaption of the common rand48 generator which can be found in C (man drand48), Java and attributed to Donald Knuth.
java.lang.String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface elki.distance.Distance

isMetric, isSquared, isSymmetric

Field Detail

STATIC

public static final RandomStableDistance STATIC

Static instance

seed

private long seed

Seed for reproducible random.

Constructor Detail

RandomStableDistance

public RandomStableDistance(long seed)

Constructor. Usually it is preferred to use the static instance!

Method Detail

distance

public double distance(DBIDRef o1,
                       DBIDRef o2)

Description copied from interface: DBIDDistance

Returns the distance between the two objects specified by their object ids.

Specified by:

distance in interface DBIDDistance

Parameters:

o1 - first object id

o2 - second object id

Returns:

the distance between the two objects specified by their object ids

pseudoRandom

private double pseudoRandom(long seed,
                            int input)

Pseudo random number generator, adaption of the common rand48 generator which can be found in C (man drand48), Java and attributed to Donald Knuth.

Parameters:

seed - Seed value

input - Input code

Returns:

Pseudo random double value

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

getInputTypeRestriction

public TypeInformation getInputTypeRestriction()

Description copied from interface: Distance

Get the input data type of the function.

Specified by:

getInputTypeRestriction in interface Distance<DBID>

Returns:

Type restriction

instantiate

public <T extends DBID> DistanceQuery<T> instantiate(Relation<T> relation)

Description copied from interface: Distance

Instantiate with a database to get the actual distance query.

Specified by:

instantiate in interface Distance<DBID>

Parameters:

relation - The representation to use

Returns:

Actual distance query.