Quicksort - Performance

This section provides a tutorial on how to measure the performance of the Quicksort algorithm. My first Java implementation of Quicksort is performing somewhere between O(N*Log2(N) and O(N*N) order levels.

Now let's see how my Java implementation of the Quicksort algorithm performs. I tried this implementation with my SortTest.java under JDK 1.3.1. Here are the results:

Array size: 10000
Average sorting time: 18 milliseconds
Number of tests: 1000
Performance: 1.8 O(N) nanoseconds
Performance: 0.13546349804879154 O(N*Log2(N)) nanoseconds
Performance: 1.8E-4 O(N*N) nanoseconds

Array size: 20000
Average sorting time: 48 milliseconds
Number of tests: 1000
Performance: 2.4 O(N) nanoseconds
Performance: 0.16797650570256523 O(N*Log2(N)) nanoseconds
Performance: 1.2E-4 O(N*N) nanoseconds

Array size: 30000
Average sorting time: 82 milliseconds
Number of tests: 1000
Performance: 2.7333333333333334 O(N) nanoseconds
Performance: 0.18378222850546175 O(N*Log2(N)) nanoseconds
Performance: 9.11111111111111E-5 O(N*N) nanoseconds

The performance of this implementation is definitely better than the insertion sort and the selection sort. The numbers tell us that it's between O(N*Log2(N) and O(N*N).

But this implementation is still not good as the JDK implementation java.util.Arras.sort(), which gives about constant performance of 0.157 O(N*Log2(N)).

Last update: 2011.

Table of Contents

 About This Book

 Introduction of Sorting Algorithms

 Java API for Sorting Algorithms

 Insertion Sort Algorithm and Implementation

 Selection Sort Algorithm and Implementation

 Bubble Sort Algorithm and Implementation

Quicksort Algorithm and Implementation

 Quicksort - Algorithm Introduction

 Quicksort - Java Implementation

Quicksort - Performance

 Quicksort - Implementation Improvements

 Merge Sort Algorithm and Implementation

 Heap Sort Algorithm and Implementation

 Shell Sort Algorithm and Implementation

 Performance Summary of Java Implementations

 References

 PDF Printing Version