Module org.apache.lucene.sandbox

Package org.apache.lucene.sandbox.codecs.quantization

Class SampleReader

java.lang.Object

org.apache.lucene.index.KnnVectorValues

org.apache.lucene.index.FloatVectorValues

org.apache.lucene.sandbox.codecs.quantization.SampleReader

All Implemented Interfaces:

HasIndexSlice

public class SampleReader
extends FloatVectorValues
implements HasIndexSlice

A reader of vector values that samples a subset of the vectors.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.index.KnnVectorValues

KnnVectorValues.DocIndexIterator

Field Summary

Fields

Modifier and Type	Field	Description
private final FloatVectorValues	origin
private final IntUnaryOperator	sampleFunction
private final int	sampleSize

Constructor Summary

Constructors

Constructor	Description
SampleReader(FloatVectorValues origin, int sampleSize, IntUnaryOperator sampleFunction)

Method Summary

Modifier and Type	Method	Description
FloatVectorValues	copy()	Creates a new copy of this KnnVectorValues.
static SampleReader	createSampleReader(FloatVectorValues origin, int k, long seed)
int	dimension()	Return the dimension of the vectors
Bits	getAcceptOrds(Bits acceptDocs)	Returns a Bits accepting docs accepted by the argument and having a vector value
IndexInput	getSlice()	Returns an IndexInput from which to read this instance's values.
int	getVectorByteLength()	Returns the vector byte length, defaults to dimension multiplied by float byte size
int	ordToDoc(int ord)	Return the docid of the document indexed with the given vector ordinal.
static int[]	reservoirSample(int n, int k, long seed)	Sample k elements from n elements according to reservoir sampling algorithm.
static int[]	reservoirSampleFromArray(int[] origin, int k, long seed)	Sample k elements from the origin array using reservoir sampling algorithm.
int	size()	Return the number of vectors for this field.
float[]	vectorValue(int targetOrd)	Return the vector value for the given vector ordinal which must be in [0, size() - 1], otherwise IndexOutOfBoundsException is thrown.

Methods inherited from class org.apache.lucene.index.FloatVectorValues

checkField, fromFloats, getEncoding, scorer

Methods inherited from class org.apache.lucene.index.KnnVectorValues

createDenseIterator, createSparseIterator, fromDISI, iterator

Methods inherited from class java.lang.Object

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

Field Details

origin

private final FloatVectorValues origin

sampleSize

private final int sampleSize

sampleFunction

private final IntUnaryOperator sampleFunction

Constructor Details

SampleReader

SampleReader(FloatVectorValues origin,
 int sampleSize,
 IntUnaryOperator sampleFunction)

Method Details

size

public int size()

Description copied from class: KnnVectorValues

Return the number of vectors for this field.

Specified by:

size in class KnnVectorValues

Returns:

the number of vectors returned by this iterator

dimension

public int dimension()

Description copied from class: KnnVectorValues

Return the dimension of the vectors

Specified by:

dimension in class KnnVectorValues

copy

public FloatVectorValues copy()
                       throws IOException

Description copied from class: KnnVectorValues

Creates a new copy of this KnnVectorValues. This is helpful when you need to access different values at once, to avoid overwriting the underlying vector returned.

Specified by:

copy in class FloatVectorValues

Throws:

IOException

getSlice

public IndexInput getSlice()

Description copied from interface: HasIndexSlice

Returns an IndexInput from which to read this instance's values.

Specified by:

getSlice in interface HasIndexSlice

vectorValue

public float[] vectorValue(int targetOrd)
                    throws IOException

Description copied from class: FloatVectorValues

Return the vector value for the given vector ordinal which must be in [0, size() - 1], otherwise IndexOutOfBoundsException is thrown. The returned array may be shared across calls.

Specified by:

vectorValue in class FloatVectorValues

Returns:

the vector value

Throws:

IOException

getVectorByteLength

public int getVectorByteLength()

Description copied from class: KnnVectorValues

Returns the vector byte length, defaults to dimension multiplied by float byte size

Overrides:

getVectorByteLength in class KnnVectorValues

ordToDoc

public int ordToDoc(int ord)

Description copied from class: KnnVectorValues

Return the docid of the document indexed with the given vector ordinal. This default implementation returns the argument and is appropriate for dense values implementations where every doc has a single value.

Overrides:

ordToDoc in class KnnVectorValues

getAcceptOrds

public Bits getAcceptOrds(Bits acceptDocs)

Description copied from class: KnnVectorValues

Returns a Bits accepting docs accepted by the argument and having a vector value

Overrides:

getAcceptOrds in class KnnVectorValues

createSampleReader

public static SampleReader createSampleReader(FloatVectorValues origin,
 int k,
 long seed)

reservoirSample

public static int[] reservoirSample(int n,
 int k,
 long seed)

Sample k elements from n elements according to reservoir sampling algorithm.

Parameters:

n - number of elements

k - number of samples

seed - random seed

Returns:

array of k samples

reservoirSampleFromArray

public static int[] reservoirSampleFromArray(int[] origin,
 int k,
 long seed)

Sample k elements from the origin array using reservoir sampling algorithm.

Parameters:

origin - original array

k - number of samples

seed - random seed

Returns:

array of k samples