me.lemire.integercompression
Class OptPFDS16

java.lang.Object
  me.lemire.integercompression.OptPFDS16

All Implemented Interfaces:

IntegerCODEC

public final class OptPFDS16
extends Object
implements IntegerCODEC

OptPFD based on Simple16 by Yan et al.

Follows:

H. Yan, S. Ding, T. Suel, Inverted index compression and query processing with optimized document ordering, in: WWW 09, 2009, pp. 401--410.

using Simple16 as the secondary coder. It encodes integers in blocks of 128 integers. For arrays containing an arbitrary number of integers, you should use it in conjunction with another CODEC:

IntegerCODEC ic = new Composition(new OptPFDS16(), new VariableByte()).

Note that this does not use differential coding: if you are working on sorted lists, you must compute the deltas separately. For multi-threaded applications, each thread should use its own OptPFDS16 object.

Author:

Daniel Lemire

Field Summary

protected static int[]	bits
protected static int[]	invbits

Constructor Summary

OptPFDS16()
Constructor for the OptPFDS16 CODEC.

Method Summary

void	compress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos) Compress data from an array to another array.
protected void	getBestBFromData(int[] in, int pos, IntWrapper bestb, IntWrapper bestexcept)
String	toString()
void	uncompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos) Uncompress data from an array to another array.

Methods inherited from class java.lang.Object

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

Field Detail

bits

protected static final int[] bits

invbits

protected static final int[] invbits

Constructor Detail

OptPFDS16

public OptPFDS16()

Constructor for the OptPFDS16 CODEC.

Method Detail

compress

public void compress(int[] in,
                     IntWrapper inpos,
                     int inlength,
                     int[] out,
                     IntWrapper outpos)

Description copied from interface: IntegerCODEC

Compress data from an array to another array. Both inpos and outpos are modified to represent how much data was read and written to if 12 ints (inlength = 12) are compressed to 3 ints, then inpos will be incremented by 12 while outpos will be incremented by 3 we use IntWrapper to pass the values by reference.

Specified by:

compress in interface IntegerCODEC

Parameters:

in - input array

inpos - location in the input array

inlength - how many integers to compress

out - output array

outpos - where to write in the output array

getBestBFromData

protected void getBestBFromData(int[] in,
                                int pos,
                                IntWrapper bestb,
                                IntWrapper bestexcept)

uncompress

public void uncompress(int[] in,
                       IntWrapper inpos,
                       int inlength,
                       int[] out,
                       IntWrapper outpos)

Description copied from interface: IntegerCODEC

Uncompress data from an array to another array. Both inpos and outpos parameters are modified to indicate new positions after read/write.

Specified by:

uncompress in interface IntegerCODEC

Parameters:

in - array containing data in compressed form

inpos - where to start reading in the array

inlength - length of the compressed data (ignored by some schemes)

out - array where to write the compressed output

outpos - where to write the compressed output in out

toString

public String toString()

Overrides:

toString in class Object