net.sf.cglib.util

Class ParallelSorter

java.lang.Object

net.sf.cglib.util.ParallelSorter

public abstract class ParallelSorter
extends Object

For the efficient sorting of multiple arrays in parallel.

Given two arrays of equal length and varying types, the standard technique for sorting them in parallel is to create a new temporary object for each row, store the objects in a temporary array, sort the array using a custom comparator, and the extract the original values back into their respective arrays. This is wasteful in both time and memory.

This class generates bytecode customized to the particular set of arrays you need to sort, in such a way that both arrays are sorted in-place, simultaneously.

Two sorting algorithms are provided. Quicksort is best when you only need to sort by a single column, as it requires very few comparisons and swaps. Mergesort is best used when sorting multiple columns, as it is a "stable" sort--that is, it does not affect the relative order of equal objects from previous sorts.

The mergesort algorithm here is an "in-place" variant, which while slower, does not require a temporary array.

Author:

Chris Nokleberg

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ParallelSorter.Generator

Field Summary

Fields

Modifier and Type	Field and Description
protected Object[]	a

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ParallelSorter()

Method Summary

Methods

Modifier and Type	Method and Description
protected int	compare(int i, int j)
static ParallelSorter	create(Object[] arrays) Create a new ParallelSorter object for a set of arrays.
void	mergeSort(int index)
void	mergeSort(int index, Comparator cmp) Sort the arrays using an in-place merge sort.
protected void	mergeSort(int lo, int hi)
void	mergeSort(int index, int lo, int hi) Sort the arrays using an in-place merge sort.
void	mergeSort(int index, int lo, int hi, Comparator cmp) Sort the arrays using an in-place merge sort.
abstract ParallelSorter	newInstance(Object[] arrays)
void	quickSort(int index) Sort the arrays using the quicksort algorithm.
void	quickSort(int index, Comparator cmp) Sort the arrays using the quicksort algorithm.
protected void	quickSort(int lo, int hi)
void	quickSort(int index, int lo, int hi) Sort the arrays using the quicksort algorithm.
void	quickSort(int index, int lo, int hi, Comparator cmp) Sort the arrays using the quicksort algorithm.
protected abstract void	swap(int i, int j)

Methods inherited from class java.lang.Object

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

Field Detail

a

protected Object[] a

Constructor Detail

ParallelSorter

protected ParallelSorter()

Method Detail

newInstance

public abstract ParallelSorter newInstance(Object[] arrays)

create

public static ParallelSorter create(Object[] arrays)

Create a new ParallelSorter object for a set of arrays. You may sort the arrays multiple times via the same ParallelSorter object.

Parameters:

arrays - An array of arrays to sort. The arrays may be a mix of primitive and non-primitive types, but should all be the same length.

loader - ClassLoader for generated class, uses "current" if null

quickSort

public void quickSort(int index)

Sort the arrays using the quicksort algorithm.

Parameters:

index - array (column) to sort by

quickSort

public void quickSort(int index,
             int lo,
             int hi)

Sort the arrays using the quicksort algorithm.

Parameters:

index - array (column) to sort by

lo - starting array index (row), inclusive

hi - ending array index (row), exclusive

quickSort

public void quickSort(int index,
             Comparator cmp)

Sort the arrays using the quicksort algorithm.

Parameters:

index - array (column) to sort by

cmp - Comparator to use if the specified column is non-primitive

quickSort

public void quickSort(int index,
             int lo,
             int hi,
             Comparator cmp)

Sort the arrays using the quicksort algorithm.

Parameters:

index - array (column) to sort by

lo - starting array index (row), inclusive

hi - ending array index (row), exclusive

cmp - Comparator to use if the specified column is non-primitive

mergeSort

public void mergeSort(int index)

Parameters:

index - array (column) to sort by

mergeSort

public void mergeSort(int index,
             int lo,
             int hi)

Sort the arrays using an in-place merge sort.

Parameters:

index - array (column) to sort by

lo - starting array index (row), inclusive

hi - ending array index (row), exclusive

mergeSort

public void mergeSort(int index,
             Comparator cmp)

Sort the arrays using an in-place merge sort.

Parameters:

index - array (column) to sort by

lo - starting array index (row), inclusive

hi - ending array index (row), exclusive

mergeSort

public void mergeSort(int index,
             int lo,
             int hi,
             Comparator cmp)

Sort the arrays using an in-place merge sort.

Parameters:

index - array (column) to sort by

lo - starting array index (row), inclusive

hi - ending array index (row), exclusive

cmp - Comparator to use if the specified column is non-primitive

compare

protected int compare(int i,
          int j)

swap

protected abstract void swap(int i,
        int j)

quickSort

protected void quickSort(int lo,
             int hi)

mergeSort

protected void mergeSort(int lo,
             int hi)