ivory.ffg.data

Class DocumentVectorUtility

java.lang.Object

ivory.ffg.data.DocumentVectorUtility

public class DocumentVectorUtility
extends Object

Auxiliary functions

Author:

Nima Asadi

Field Summary

Fields

Modifier and Type	Field and Description
static int	BLOCK_SIZE
static int	MAX_POSITIONS

Constructor Summary

Constructors

Constructor and Description
DocumentVectorUtility()

Method Summary

Methods

Modifier and Type	Method and Description
static int[][]	compressData(int[] data, int blockSize, boolean computeGaps) Compresses positions using PForDelta compression
static int[]	deserializePositions(byte[] bytes) Deserializes the gamma-encoded positions.
static int[][]	getPositions(int[] doc, int[] terms) Given a document vector and an array of query terms, this function constructs the positions.
static int	lastBlockSize(int dataLength, int nbBlocks, int blockSize)
static DocumentVector	newInstance(String documentVectorClass, IntDocVector document) Factory method
static DocumentVector	readInstance(String documentVectorClass, DataInput input) Reads an instance of DocumentVector from input
static byte[]	serializePositions(int[] positions) Serializes the positions using gamma codes

Methods inherited from class java.lang.Object

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

Field Detail

BLOCK_SIZE

public static final int BLOCK_SIZE

See Also:

Constant Field Values

MAX_POSITIONS

public static final int MAX_POSITIONS

See Also:

Constant Field Values

Constructor Detail

DocumentVectorUtility

public DocumentVectorUtility()

Method Detail

compressData

public static int[][] compressData(int[] data,
                   int blockSize,
                   boolean computeGaps)

Compresses positions using PForDelta compression

Returns:

Serialized positions (using PForDelta)

deserializePositions

public static int[] deserializePositions(byte[] bytes)
                                  throws IOException

Deserializes the gamma-encoded positions.

Parameters:

bytes - Serialized positions

Returns:

A decoded integer array of positions

Throws:

IOException

getPositions

public static int[][] getPositions(int[] doc,
                   int[] terms)

Given a document vector and an array of query terms, this function constructs the positions.

Parameters:

doc - Document vector

terms - Query terms

Returns:

Position array for every query term

lastBlockSize

public static int lastBlockSize(int dataLength,
                int nbBlocks,
                int blockSize)

newInstance

public static DocumentVector newInstance(String documentVectorClass,
                         IntDocVector document)
                                  throws Exception

Factory method

Parameters:

documentVectorClass - DocumentVector class

document - IntDocVector (term positions start from 1)

Returns:

New DocumentVector (term positions start from 1)

Throws:

Exception

readInstance

public static DocumentVector readInstance(String documentVectorClass,
                          DataInput input)
                                   throws Exception

Reads an instance of DocumentVector from input

Parameters:

input - DataInput

documentVectorClass - DocumentVector class

Returns:

DocumentVector object

Throws:

Exception

serializePositions

public static byte[] serializePositions(int[] positions)
                                 throws IOException

Serializes the positions using gamma codes

Parameters:

positions - Array of positions for a term

Returns:

Serialized positions (using gamma codes)

Throws:

IOException