Package it.unimi.di.big.mg4j.io
Class InterpolativeCoding
 java.lang.Object

 it.unimi.di.big.mg4j.io.InterpolativeCoding

public final class InterpolativeCoding extends Object
Static methods implementing interpolative coding.Interpolative coding is a sophisticated compression technique that can be applied to increasing sequences of integers. It is based on the idea that, for instance, when compressing the sequence 2 5 6 we already know that between 2 and 6 there are only 3 integers, so if we already know that the middle integer is between 2 and 6 we can use a small index to denote 5 among 3, 4, and 5.
The main limitation of interpolative coding is that it needs to code and decode the entire sequence in an array. This, however, makes it very suitable to code the positions of the occurrences of a term in a document, in particular in short documents.
 Since:
 0.6
 Author:
 Sebastiano Vigna


Method Summary
Modifier and Type Method Description static void
read(InputBitStream in, int[] data, int offset, int len, int lo, int hi)
Reads from a bit stream an increasing sequence of integers coded using interpolative coding.static int
write(OutputBitStream out, int[] data, int offset, int len, int lo, int hi)
Writes to a bit stream a increasing sequence of integers using interpolative coding.



Method Detail

write
public static int write(OutputBitStream out, int[] data, int offset, int len, int lo, int hi) throws IOException
Writes to a bit stream a increasing sequence of integers using interpolative coding.Note that the length of the sequence and the arguments
lo
andhi
must be known at decoding time. Parameters:
out
 the output bit stream.data
 the vector containing the integer sequence.offset
 the offset intodata
where the sequence starts.len
 the number of integers to code.lo
 a lower bound (must be smaller than or equal to the first integer in the sequence).hi
 an upper bound (must be greater than or equal to the last integer in the sequence). Returns:
 the number of written bits.
 Throws:
IOException

read
public static void read(InputBitStream in, int[] data, int offset, int len, int lo, int hi) throws IOException
Reads from a bit stream an increasing sequence of integers coded using interpolative coding. Parameters:
in
 the input bit stream.data
 the vector that will store the sequence; it may benull
, in which case the integers are discarded.offset
 the offset intodata
where to store the result.len
 the number of integers to decode.lo
 a lower bound (the same as the one given towrite()
).hi
 an upper bound (the same as the one given towrite()
). Throws:
IOException

