com.topologi.diffx.algorithm

Class DiffXKumarRangan

java.lang.Object

com.topologi.diffx.algorithm.DiffXAlgorithmBase

com.topologi.diffx.algorithm.DiffXKumarRangan

All Implemented Interfaces:

DiffXAlgorithm

public final class DiffXKumarRangan
extends DiffXAlgorithmBase

Performs the diff comparison using an optimized version of the linear space algorithm of S.Kiran Kumar and C.Pandu Rangan.

Implementation note: this algorithm effectively detects the correct changes in the sequences, but suffers from two main problems:

• When the events are formatted directly from reading the matrix, the XML is not necessarily well-formed, this occurs mostly when some elements are swapped, because the closing tags will not necessarily reported in an order that allows the XML to be well-formed.
  Using the SmartXMLFormatter helps in solving the problem as it maintains a stack of the elements that are being written and actually ignores the name of the closing element, so all the elements are closed properly.

For S. Kiran Kumar and C. Pandu Rangan. A linear space algorithm for the LCS problem, Acta Informatica. Volume 24 , Issue 3 (June 1987); Copyright Springer-Verlag 1987

This class reuses portions of code originally written by Mikko Koivisto and Tuomo Saarni.

http://dblp.uni-trier.de/rec/bibtex/journals/acta/KumarR87

http://users.utu.fi/~tuiisa/Java/

Version:

9 March 2005

Author:

Christophe Lauret

Field Summary

Fields inherited from class com.topologi.diffx.algorithm.DiffXAlgorithmBase

length1, length2, sequence1, sequence2

Constructor Summary

Constructors

Constructor and Description
DiffXKumarRangan(EventSequence seq0, EventSequence seq1) Creates a new DiffXAlgorithmBase.

Method Summary

Modifier and Type	Method and Description
int	length() Calculates the length of LCS and returns it.
void	process(DiffXFormatter formatter) Writes the diff sequence using the specified formatter.

Methods inherited from class com.topologi.diffx.algorithm.DiffXAlgorithmBase

getFirstSequence, getSecondSequence

Methods inherited from class java.lang.Object

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

Constructor Detail

DiffXKumarRangan

public DiffXKumarRangan(EventSequence seq0,
                        EventSequence seq1)

Creates a new DiffXAlgorithmBase.

Parameters:

seq0 - The first sequence to compare.

seq1 - The second sequence to compare.

Method Detail

length

public int length()

Calculates the length of LCS and returns it.

If the length is calculated already it'll not be calculated repeatedly.

This algorithm starts from the length of the first sequence as the maximum possible LCS and reduces the length for every difference with the second sequence.

The time complexity is O(n(m-p)) and the space complexity is O(n+m).

Returns:

The length of LCS

process

public void process(DiffXFormatter formatter)
             throws IOException

Writes the diff sequence using the specified formatter.

Parameters:

formatter - The formatter that will handle the output.

Throws:

IOException - If thrown by the formatter.