Java example source code file (HashSetvBitSetTest.java)

This example Java source code file (HashSetvBitSetTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bitset, hashset, hashsetvbitsettest, integer, loops, loops2, suppresswarnings, test, util

The HashSetvBitSetTest.java Java example source code

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.lang3;

import java.util.BitSet;
import java.util.HashSet;

import org.junit.Assert;
import org.junit.Test;

/**
 * Test to show whether using BitSet for removeAll() methods is faster than using HashSet.
 */
public class HashSetvBitSetTest {

    private static final int LOOPS = 2000; // number of times to invoke methods
    private static final int LOOPS2 = 10000;

    @Test
    public void testTimes() {
        timeHashSet(10); // warmup
        timeBitSet(10); // warmup
        long timeDiff = printTimes(0);
        timeDiff += printTimes(5);
        timeDiff += printTimes(10);
        timeDiff += printTimes(200);
        timeDiff += printTimes(50);
        timeDiff += printTimes(100);
        timeDiff += printTimes(1000);
        timeDiff += printTimes(2000);
        Assert.assertTrue(timeDiff <= 0);
    }

    /**
     * @return bitSet - HashSet
     */
    private long printTimes(final int count) {
        final long hashSet = timeHashSet(count);
        final long bitSet = timeBitSet(count);
        // If percent is less than 100, then bitset is faster
        System.out.println("Ratio="+(bitSet*100/hashSet)+"% count="+count+" hash="+hashSet+" bits="+bitSet);
        return bitSet - hashSet;
    }

    private static long timeHashSet(final int count) {
        int [] result = new int[0];
        final long start = System.nanoTime();
        for (int i = 0; i < LOOPS; i++) {
            result = testHashSet(count);
        }
        final long elapsed = System.nanoTime() - start;
        Assert.assertEquals(count, result.length);
        return elapsed;
    }

    private static long timeBitSet(final int count) {
        int [] result = new int[0];
        final long start = System.nanoTime();
        for (int i = 0; i < LOOPS; i++) {
            result = testBitSet(count);
        }
        final long elapsed = System.nanoTime() - start;
        Assert.assertEquals(count, result.length);
        return elapsed;
    }

    @SuppressWarnings("boxing")
    private static int[] testHashSet(final int count) {
        final HashSet<Integer> toRemove = new HashSet();
            int found = 0;
            for (int i = 0; i < count; i++) {
                toRemove.add(found++);
            }
            return extractIndices(toRemove);
        }
    
    private static int[] testBitSet(final int count) {
        final BitSet toRemove = new BitSet();
        int found = 0;
        for (int i = 0; i < count; i++) {
            toRemove.set(found++);
        }
        return extractIndices(toRemove);
    }
    

    private static int[] extractIndices(final HashSet<Integer> coll) {
        final int[] result = new int[coll.size()];
        int i = 0;
        for (final Integer index : coll) {
            result[i++] = index.intValue();
        }
        return result;
    }

    private static int[] extractIndices(final BitSet coll) {
        final int[] result = new int[coll.cardinality()];
        int i = 0;
        int j=0;
        while((j=coll.nextSetBit(j)) != -1) {
            result[i++] = j++;            
        }
        return result;
    }
    
    @Test
    public void testTimesExtractOrBitset() {
        final BitSet toRemove = new BitSet();
        final int[] array = new int[100];
        toRemove.set(10, 20);
        timeBitSetRemoveAll(array, toRemove); // warmup
        timeExtractRemoveAll(array, toRemove); // warmup
        long timeDiff = printTimes(100,1);
        timeDiff += printTimes(100,10);
        timeDiff += printTimes(100,50);
        timeDiff += printTimes(100,100);
        timeDiff += printTimes(1000,10);
        timeDiff += printTimes(1000,100);
        timeDiff += printTimes(1000,500);
        timeDiff += printTimes(1000,1000);
        Assert.assertTrue(timeDiff <= 0);
    }

    private long printTimes(final int arraySize, final int bitSetSize) {
        final int[] array = new int[arraySize];
        final BitSet remove = new BitSet();
        for (int i = 0; i < bitSetSize; i++) {
            remove.set(i);
        }
        final long bitSet = timeBitSetRemoveAll(array, remove );
        final long extract = timeExtractRemoveAll(array, remove);
        // If percent is less than 100, then direct use of bitset is faster
        System.out.println("Ratio="+(bitSet*100/extract)+"% array="+array.length+" count="+remove.cardinality()+" extract="+extract+" bitset="+bitSet);
        return bitSet - extract;
    }

    private long timeBitSetRemoveAll(final int[] array, final BitSet toRemove) {
        int[] output = new int[0];
        final long start = System.nanoTime();
        for(int i = 0; i < LOOPS2; i++){
            output = (int[]) ArrayUtils.removeAll(array, toRemove);            
        }
        final long end = System.nanoTime();
        Assert.assertEquals(array.length-toRemove.cardinality(), output.length);
        return end - start;
    }
    
    private long timeExtractRemoveAll(final int[] array, final BitSet toRemove) {
        int[] output = new int[0];
        final long start = System.nanoTime();
        for(int i = 0; i < LOOPS2; i++){
            final int[] extractIndices = extractIndices(toRemove);
            output = (int[]) ArrayUtils.removeAll((Object)array, extractIndices);
        }
        final long end = System.nanoTime();
        Assert.assertEquals(array.length-toRemove.cardinality(), output.length);
        return end - start;
    }
    
}