org.openimaj.lsh.functions

Class DoubleHyperplaneCosineFactory

java.lang.Object

org.openimaj.lsh.functions.RandomisedHashFunctionFactory<double[]>

org.openimaj.lsh.functions.DoubleHashFunctionFactory

org.openimaj.lsh.functions.DoubleHyperplaneCosineFactory

All Implemented Interfaces:

HashFunctionFactory<double[]>

@Reference(type=Inproceedings,
           author="Charikar, Moses S.",
           title="Similarity estimation techniques from rounding algorithms",
           year="2002",
           booktitle="Proceedings of the thiry-fourth annual ACM symposium on Theory of computing",
           pages={"380","","388"},
           url="http://doi.acm.org/10.1145/509907.509965",
           publisher="ACM",
           series="STOC \'02")
public class DoubleHyperplaneCosineFactory
extends DoubleHashFunctionFactory

A hash function factory that produces hash functions that approximate cosine distance using hyperplanes.

The hash function hashes the input vector into a binary value (i.e. 0 or 1). A random vector on the surface of a hypersphere is generated during construction. The hash code is computed by calculating the dot product of the random vector with the input vector and testing to see whether the value is greater than or equal to 0 (1 is output) or less than 0 (0 is output).

Author:

Jonathon Hare (jsh2@ecs.soton.ac.uk)

Field Summary

Fields inherited from class org.openimaj.lsh.functions.RandomisedHashFunctionFactory

ndims, rng

Constructor Summary

Constructors

Constructor and Description
DoubleHyperplaneCosineFactory(int ndims, cern.jet.random.engine.MersenneTwister rng) Construct with the given arguments.

Method Summary

Modifier and Type	Method and Description
org.openimaj.lsh.functions.DoubleHyperplaneCosineFactory.Function	create() Construct a new HashFunction.
protected DoubleFVComparison	fvDistanceFunction()

Methods inherited from class org.openimaj.lsh.functions.DoubleHashFunctionFactory

distanceFunction

Methods inherited from class java.lang.Object

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

Constructor Detail

DoubleHyperplaneCosineFactory

public DoubleHyperplaneCosineFactory(int ndims,
                                     cern.jet.random.engine.MersenneTwister rng)

Construct with the given arguments.

Parameters:

ndims - The number of dimensions

rng - A random number generator

Method Detail

create

public org.openimaj.lsh.functions.DoubleHyperplaneCosineFactory.Function create()

Description copied from interface: HashFunctionFactory

Construct a new HashFunction.

Returns:

the new HashFunction

fvDistanceFunction

protected DoubleFVComparison fvDistanceFunction()

Specified by:

fvDistanceFunction in class DoubleHashFunctionFactory