/*
* Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This source code is provided to illustrate the usage of a given feature
* or technique and has been deliberately simplified. Additional steps
* required for a production-quality application, such as security checks,
* input validation and proper error handling, might not be present in
* this sample code.
*/
import java.util.Arrays;
import java.util.Random;
import static java.lang.Integer.parseInt;
/**
* MergeExample is a class that runs a demo benchmark of the {@code ForkJoin} framework
* by benchmarking a {@link MergeSort} algorithm that is implemented using
* {@link java.util.concurrent.RecursiveAction}.
* The {@code ForkJoin} framework is setup with different parallelism levels
* and the sort is executed with arrays of different sizes to see the
* trade offs by using multiple threads for different sizes of the array.
*/
public class MergeDemo {
// Use a fixed seed to always get the same random values back
private final Random random = new Random(759123751834L);
private static final int ITERATIONS = 10;
/**
* Represents the formula {@code f(n) = start + (step * n)} for n = 0 & n < iterations
*/
private static class Range {
private final int start;
private final int step;
private final int iterations;
private Range(int start, int step, int iterations) {
this.start = start;
this.step = step;
this.iterations = iterations;
}
/**
* Parses start, step and iterations from args
* @param args the string array containing the arguments
* @param start which element to start the start argument from
* @return the constructed range
*/
public static Range parse(String[] args, int start) {
if (args.length < start + 3) {
throw new IllegalArgumentException("Too few elements in array");
}
return new Range(parseInt(args[start]), parseInt(args[start + 1]), parseInt(args[start + 2]));
}
public int get(int iteration) {
return start + (step * iteration);
}
public int getIterations() {
return iterations;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
builder.append(start).append(" ").append(step).append(" ").append(iterations);
return builder.toString();
}
}
/**
* Wraps the different parameters that is used when running the MergeExample.
* {@code sizes} represents the different array sizes
* {@code parallelism} represents the different parallelism levels
*/
private static class Configuration {
private final Range sizes;
private final Range parallelism;
private final static Configuration defaultConfig = new Configuration(new Range(20000, 20000, 10),
new Range(2, 2, 10));
private Configuration(Range sizes, Range parallelism) {
this.sizes = sizes;
this.parallelism = parallelism;
}
/**
* Parses the arguments and attempts to create a configuration containing the
* parameters for creating the array sizes and parallelism sizes
* @param args the input arguments
* @return the configuration
*/
public static Configuration parse(String[] args) {
if (args.length == 0) {
return defaultConfig;
} else {
try {
if (args.length == 6) {
return new Configuration(Range.parse(args, 0), Range.parse(args, 3));
}
} catch (NumberFormatException e) {
System.err.println("MergeExample: error: Argument was not a number.");
}
System.err.println("MergeExample <size start> <size step> <size steps> <parallel start> <parallel step>" +
" <parallel steps>");
System.err.println("example: MergeExample 20000 10000 3 1 1 4");
System.err.println("example: will run with arrays of sizes 20000, 30000, 40000" +
" and parallelism: 1, 2, 3, 4");
return null;
}
}
/**
* Creates an array for reporting the test result time in
* @return an array containing {@code sizes.iterations * parallelism.iterations} elements
*/
private long[][] createTimesArray() {
return new long[sizes.getIterations()][parallelism.getIterations()];
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder("");
if (this == defaultConfig) {
builder.append("Default configuration. ");
}
builder.append("Running with parameters: ");
builder.append(sizes);
builder.append(" ");
builder.append(parallelism);
return builder.toString();
}
}
/**
* Generates an array of {@code elements} random elements
* @param elements the number of elements requested in the array
* @return an array of {@code elements} random elements
*/
private int[] generateArray(int elements) {
int[] array = new int[elements];
for (int i = 0; i < elements; ++i) {
array[i] = random.nextInt();
}
return array;
}
/**
* Runs the test
* @param config contains the settings for the test
*/
private void run(Configuration config) {
Range sizes = config.sizes;
Range parallelism = config.parallelism;
// Run a couple of sorts to make the JIT compile / optimize the code
// which should produce somewhat more fair times
warmup();
long[][] times = config.createTimesArray();
for (int size = 0; size < sizes.getIterations(); size++) {
runForSize(parallelism, sizes.get(size), times, size);
}
printResults(sizes, parallelism, times);
}
/**
* Prints the results as a table
* @param sizes the different sizes of the arrays
* @param parallelism the different parallelism levels used
* @param times the median times for the different sizes / parallelism
*/
private void printResults(Range sizes, Range parallelism, long[][] times) {
System.out.println("Time in milliseconds. Y-axis: number of elements. X-axis parallelism used.");
long[] sums = new long[times[0].length];
System.out.format("%8s ", "");
for (int i = 0; i < times[0].length; i++) {
System.out.format("%4d ", parallelism.get(i));
}
System.out.println("");
for (int size = 0; size < sizes.getIterations(); size++) {
System.out.format("%8d: ", sizes.get(size));
for (int i = 0; i < times[size].length; i++) {
sums[i] += times[size][i];
System.out.format("%4d ", times[size][i]);
}
System.out.println("");
}
System.out.format("%8s: ", "Total");
for (long sum : sums) {
System.out.format("%4d ", sum);
}
System.out.println("");
}
private void runForSize(Range parallelism, int elements, long[][] times, int size) {
for (int step = 0; step < parallelism.getIterations(); step++) {
long time = runForParallelism(ITERATIONS, elements, parallelism.get(step));
times[size][step] = time;
}
}
/**
* Runs <i>iterations</i> number of test sorts of a random array of <i>element</i> length
* @param iterations number of iterations
* @param elements number of elements in the random array
* @param parallelism parallelism for the ForkJoin framework
* @return the median time of runs
*/
private long runForParallelism(int iterations, int elements, int parallelism) {
MergeSort mergeSort = new MergeSort(parallelism);
long[] times = new long[iterations];
for (int i = 0; i < iterations; i++) {
// Suggest the VM to run a garbage collection to reduce the risk of getting one
// while running the test run
System.gc();
long start = System.currentTimeMillis();
mergeSort.sort(generateArray(elements));
times[i] = System.currentTimeMillis() - start;
}
return medianValue(times);
}
/**
* Calculates the median value of the array
* @param times array of times
* @return the median value
*/
private long medianValue(long[] times) {
if (times.length == 0) {
throw new IllegalArgumentException("Empty array");
}
// Make a copy of times to avoid having side effects on the parameter value
Arrays.sort(times.clone());
long median = times[times.length / 2];
if (times.length > 1 && times.length % 2 != 0) {
median = (median + times[times.length / 2 + 1]) / 2;
}
return median;
}
/**
* Generates 1000 arrays of 1000 elements and sorts them as a warmup
*/
private void warmup() {
MergeSort mergeSort = new MergeSort(Runtime.getRuntime().availableProcessors());
for (int i = 0; i < 1000; i++) {
mergeSort.sort(generateArray(1000));
}
}
public static void main(String[] args) {
Configuration configuration = Configuration.parse(args);
if (configuration == null) {
System.exit(1);
}
System.out.println(configuration);
new MergeDemo().run(configuration);
}
}