[jdom-interest] About JDOM performance

[Alex Rosen]

Those pitfalls were not completely unintentional - my point was that the
difference in speed is insignificant, given the fact that a lot of other stuff
(allocations, method calls, etc) is likely to be going on, besides just List
manipulation. However, I cleaned up the code to get rid of as much overhead as
I could, and I increased the loop counter. The new results do show ArrayList
being about 25% faster than LinkedList. But, average time for a list operation
was still well under a millionth of a second.

--Alex


D:\z\Test2>java ListTest linked
Testing LinkedList
Time for add: 461 ms
Time for add+remove: 681 ms
Time for add+remove 2: 641 ms
Time for access: 160 ms
Time for access 2: 260 ms
Time for total ***: 2203 ms

Time for add: 411 ms
Time for add+remove: 681 ms
Time for add+remove 2: 631 ms
Time for access: 140 ms
Time for access 2: 250 ms
Time for total ***: 2113 ms

Time for add: 421 ms
Time for add+remove: 681 ms
Time for add+remove 2: 621 ms
Time for access: 150 ms
Time for access 2: 240 ms
Time for total ***: 2113 ms

Time for add: 421 ms
Time for add+remove: 671 ms
Time for add+remove 2: 621 ms
Time for access: 150 ms
Time for access 2: 240 ms
Time for total ***: 2103 ms


D:\z\Test2>java ListTest array
Testing ArrayList
Time for add: 261 ms
Time for add+remove: 651 ms
Time for add+remove 2: 450 ms
Time for access: 200 ms
Time for access 2: 121 ms
Time for total ***: 1683 ms

Time for add: 240 ms
Time for add+remove: 641 ms
Time for add+remove 2: 441 ms
Time for access: 200 ms
Time for access 2: 120 ms
Time for total ***: 1642 ms

Time for add: 240 ms
Time for add+remove: 641 ms
Time for add+remove 2: 441 ms
Time for access: 190 ms
Time for access 2: 120 ms
Time for total ***: 1632 ms

Time for add: 251 ms
Time for add+remove: 641 ms
Time for add+remove 2: 450 ms
Time for access: 191 ms
Time for access 2: 120 ms
Time for total ***: 1653 ms
-------------- next part --------------
import java.util.*;

public class ListTest
{
	public static void main(String[] args)
	{
		boolean linked = (args.length > 0 && args[0].equals("linked"));
		if (linked)
			System.out.println("Testing LinkedList");
		else
			System.out.println("Testing ArrayList");

		test(linked);
		test(linked);
		test(linked);
		test(linked);
	}

	private static void test(boolean linked)
	{
		Double[] doubles = { new Double(1.0), new Double(2.0), new Double(3.0) };

		//// Test add

		long start = System.currentTimeMillis();
		
		List list = createList(linked);
		for (int i = 0; i < 1000000; i++)
		{
			if ((i % 5) == 0)
				list.clear();
			list.add(doubles[i % 3]);
		}
		if (list.size() < 0) // Make sure HotSpot doesn't optimize away anything (just in case)
			System.exit(1);

		long inter = interval("add", start);

		//// Test add and remove from front

		list = createList(linked);
		for (int i = 0; i < 1000000; i++)
		{
			if ((i % 5) == 0)
				list.clear();
			list.add(0, doubles[i % 3]);
			if ((i % 2) == 0)
				list.remove(0);
		}
		if (list.size() < 0) // Make sure HotSpot doesn't optimize away anything (just in case)
			System.exit(1);

		inter = interval("add+remove", inter);

		//// Test add and remove from middle

		list = createList(linked);
		for (int i = 0; i < 1000000; i++)
		{
			if ((i % 5) == 0)
				list.clear();
			list.add(doubles[i % 3]);
			if ((i % 2) == 0)
				list.remove(i % list.size());
		}
		if (list.size() < 0) // Make sure HotSpot doesn't optimize away anything (just in case)
			System.exit(1);

		inter = interval("add+remove 2", inter);

		//// Test access via Iterator

		list.clear();
		for (int i = 0; i < 10; i++)
			list.add(doubles[i % 3]);

		double d = 0.0;
		for (int i = 0; i < 100000; i++) // Note: 10x fewer iterations, since we access all 10 values.
		{
			Iterator iter = list.iterator();
			while(iter.hasNext())
			{
				Double d2 = (Double)iter.next();
				d += d2.doubleValue();
			}
		}
		if (d < 0.0) // Make sure HotSpot doesn't optimize away anything (just in case)
			System.exit(1);

		inter = interval("access", inter);

		//// Test access via random access

		list.clear();
		for (int i = 0; i < 10; i++)
			list.add(doubles[i % 3]);

		d = 0.0;
		for (int i = 0; i < 1000000; i++)
		{
			Double d2 = (Double)list.get(i % 10);
			d += d2.doubleValue();
		}
		if (d < 0.0) // Make sure HotSpot doesn't optimize away anything (just in case)
			System.exit(1);

		inter = interval("access 2", inter);
		interval("total ***", start);
		System.out.println();
	}

	private static List createList(boolean linked)
	{
		if (linked) 
			return new LinkedList(); 
		else
			return new ArrayList();
	}

	private static long interval(String label, long start)
	{
		long end = System.currentTimeMillis();
		long diff = end - start;
		System.out.println("Time for " + label + ": " + diff + " ms");
		return end;
	}
}