com.kamikaze.pfordelta

Class PForDelta

java.lang.Object

com.kamikaze.pfordelta.PForDelta

public class PForDelta
extends Object

Implementation of the optimized PForDelta algorithm for sorted integer arrays. The basic ideas are based on 1. Original algorithm from http://homepages.cwi.nl/~heman/downloads/msthesis.pdf 2. Optimization and variation from http://www2008.org/papers/pdf/p387-zhangA.pdf 3. Further optimization http://www2009.org/proceedings/pdf/p401.pdf As a part of the PForDelta implementation, Simple16 is used to compress exceptions. The original Simple16 algorithm can also be found in the above literatures. This implementation overcomes the problem that Simple16 cannot deal with more than 2^28 numbers. Author: hao yan hyan2008@gmail.com

Constructor Summary

Constructors

Constructor and Description
PForDelta()

Method Summary

Modifier and Type	Method and Description
static boolean	checkBigNumbers(int[] inputBlock, int bits, int blockSize) Check if the block contains big numbers that is greater than ((1<< bits)-1)
static int[]	compressOneBlock(int[] inputBlock, int bits, int blockSize) The core implementation of compressing a block with blockSize integers using PForDelta with the given parameter b
static int[]	compressOneBlockOpt(int[] inBlock, int blockSize) Compress one block of blockSize integers using PForDelta with the optimal parameter b
static int	decompressBBitSlots(int[] outDecompSlots, int[] inCompBlock, int blockSize, int bits) Decompress b-bit slots
static int	decompressBlockByS16(int[] outDecompBlock, int[] inCompBlock, int inStartOffsetInBits, int blockSize) Decompress a block of blockSize integers using Simple16 algorithm
static int	decompressOneBlock(int[] outBlock, int[] inBlock, int blockSize) Decompress one block using PForDelta
static int	estimateCompressedSize(int[] inputBlock, int bits, int blockSize) Estimate the compressed size in ints of a block
static int	readBits(int[] in, int inOffset, int bits) Read a certain number of bits of an integer into an integer array starting from the given start offset
static void	writeBits(int[] out, int val, int outOffset, int bits) Write a certain number of bits of an integer into an integer array starting from the given start offset

Methods inherited from class java.lang.Object

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

Constructor Detail

PForDelta

public PForDelta()

Method Detail

compressOneBlockOpt

public static int[] compressOneBlockOpt(int[] inBlock,
                                        int blockSize)

Compress one block of blockSize integers using PForDelta with the optimal parameter b

Parameters:

inBlock - the block to be compressed

blockSize - the block size

Returns:

the compressed block

decompressOneBlock

public static int decompressOneBlock(int[] outBlock,
                                     int[] inBlock,
                                     int blockSize)

Decompress one block using PForDelta

Parameters:

outBlock - the block that was decompressed

inBlock - the block to be decompressed

blockSize - the number of elements in the decompressed block

Returns:

the compressed size in bits

estimateCompressedSize

public static int estimateCompressedSize(int[] inputBlock,
                                         int bits,
                                         int blockSize)

Estimate the compressed size in ints of a block

Parameters:

inputBlock - the block to be compressed

bits - the value of the parameter b

blockSize - the block size

Returns:

the compressed size in ints

checkBigNumbers

public static boolean checkBigNumbers(int[] inputBlock,
                                      int bits,
                                      int blockSize)

Check if the block contains big numbers that is greater than ((1<< bits)-1)

Parameters:

inputBlock - the block to be compressed

bits - the numbers of bits to decide whether a number is a big number

blockSize - the block size

Returns:

true if there is any big numbers in the block

compressOneBlock

public static int[] compressOneBlock(int[] inputBlock,
                                     int bits,
                                     int blockSize)

The core implementation of compressing a block with blockSize integers using PForDelta with the given parameter b

Parameters:

inputBlock - the block to be compressed

bits - the the value of the parameter b

blockSize - the block size

Returns:

the compressed block

decompressBBitSlots

public static int decompressBBitSlots(int[] outDecompSlots,
                                      int[] inCompBlock,
                                      int blockSize,
                                      int bits)

Decompress b-bit slots

Parameters:

outDecompSlots - decompressed block which is the output

inCompBlock - the compressed block which is the input

blockSize - the block size

bits - the value of the parameter b

Returns:

the compressed size in bits of the data that has been decompressed

decompressBlockByS16

public static int decompressBlockByS16(int[] outDecompBlock,
                                       int[] inCompBlock,
                                       int inStartOffsetInBits,
                                       int blockSize)

Decompress a block of blockSize integers using Simple16 algorithm

Parameters:

outDecompBlock - the decompressed block which is the output

inCompBlock - the compressed block which is the input

blockSize - the block size

inStartOffsetInBits - the start offset in bits of the compressed block

Returns:

the compressed size in bits of the data that has been decompressed

writeBits

public static final void writeBits(int[] out,
                                   int val,
                                   int outOffset,
                                   int bits)

Write a certain number of bits of an integer into an integer array starting from the given start offset

Parameters:

out - the output array

val - the integer to be written

outOffset - the start offset in bits in the output array

bits - the number of bits to be written (bits greater or equal to 0)

readBits

public static final int readBits(int[] in,
                                 int inOffset,
                                 int bits)

Read a certain number of bits of an integer into an integer array starting from the given start offset

Parameters:

in - the input array

inOffset - the start offset in bits in the input array

bits - the number of bits to be read, unlike writeBits(), readBits() does not deal with bits==0 and thus bits must be greater than 0. When bits ==0, the calling functions will just skip the entire bits-bit slots without decoding them

Returns:

the bits bits of the input