Class ParallelSorter
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
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Nested Class Summary
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Field Summary
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionprotected int
compare
(int i, int j) static ParallelSorter
Create a new ParallelSorter object for a set of arrays.void
mergeSort
(int index) 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.void
mergeSort
(int index, 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.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.void
quickSort
(int index, Comparator cmp) Sort the arrays using the quicksort algorithm.protected abstract void
swap
(int i, int j)
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Field Details
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a
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Constructor Details
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ParallelSorter
protected ParallelSorter()
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Method Details
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newInstance
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create
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.
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quickSort
public void quickSort(int index) Sort the arrays using the quicksort algorithm.- Parameters:
index
- array (column) to sort by
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quickSort
public void quickSort(int index, int lo, int hi) Sort the arrays using the quicksort algorithm.- Parameters:
index
- array (column) to sort bylo
- starting array index (row), inclusivehi
- ending array index (row), exclusive
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quickSort
Sort the arrays using the quicksort algorithm.- Parameters:
index
- array (column) to sort bycmp
- Comparator to use if the specified column is non-primitive
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quickSort
Sort the arrays using the quicksort algorithm.- Parameters:
index
- array (column) to sort bylo
- starting array index (row), inclusivehi
- ending array index (row), exclusivecmp
- Comparator to use if the specified column is non-primitive
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mergeSort
public void mergeSort(int index) - Parameters:
index
- array (column) to sort by
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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 bylo
- starting array index (row), inclusivehi
- ending array index (row), exclusive
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mergeSort
Sort the arrays using an in-place merge sort.- Parameters:
index
- array (column) to sort bycmp
- Comparator to use if the specified column is non-primitive
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mergeSort
Sort the arrays using an in-place merge sort.- Parameters:
index
- array (column) to sort bylo
- starting array index (row), inclusivehi
- ending array index (row), exclusivecmp
- Comparator to use if the specified column is non-primitive
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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)
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