set vs check then set for volatile (and non) in java

gistfile1.java

package misc.bench;

import java.util.Random;
import java.util.concurrent.atomic.AtomicIntegerArray;

import com.google.caliper.Param;
import com.google.caliper.Runner;
import com.google.caliper.SimpleBenchmark;
import com.google.common.collect.ObjectArrays;

public class CondWriteBench extends SimpleBenchmark {
  
	private static final int ARRAY_LENGTH = 1000;
	
	private final int source[]         = new int[ARRAY_LENGTH];
	private final int targetContents[] = new int[ARRAY_LENGTH];

	enum ArrayType { SAME, DIFFERENT };
	
	@Param ArrayType arrayType;
	
	@Override
	protected void setUp() throws Exception {
		Random r = new Random();
		for (int i=0; i < ARRAY_LENGTH; i++) {
			source[i] = r.nextInt() & ~1;
			targetContents[i] = arrayType == ArrayType.SAME ? source[i] : (r.nextInt() | 1);	
		}
	}
	
	public int timeCopyNoCheck(int reps) {
		int[] target = new int[ARRAY_LENGTH];
		while (reps-- > 0) {
			System.arraycopy(this.targetContents, 0, target, 0, ARRAY_LENGTH);
			for (int i=0; i < ARRAY_LENGTH; i++) {
				target[i] = source[i];
			}
		}
		return target[new Random().nextInt(ARRAY_LENGTH)];
	}
	
	public int timeCopyCheck(int reps) {
		int[] target = new int[ARRAY_LENGTH];
		while (reps-- > 0) {
			System.arraycopy(this.targetContents, 0, target, 0, ARRAY_LENGTH);
			for (int i=0; i < ARRAY_LENGTH; i++) {
				int x = source[i];
				if (target[i] != x) {
					target[i] = x;
				}
			}
		}
		return target[new Random().nextInt(ARRAY_LENGTH)];
	}
	
	public int timeCopyNoCheckAI(int reps) {
		int total = 0, rindex = new Random().nextInt(ARRAY_LENGTH);
		AtomicIntegerArray target = new AtomicIntegerArray(ARRAY_LENGTH);
		while (reps-- > 0) {
			if (arrayType == ArrayType.DIFFERENT) {
				copyToAI(targetContents, target);
			}
			for (int i=0; i < ARRAY_LENGTH; i++) {
				target.set(i, source[i]);
			}
			total += target.get(rindex);
		}
		return total;
	}
	

	public int timeCopyCheckAI(int reps) {
		int total = 0, rindex = new Random().nextInt(ARRAY_LENGTH);
		AtomicIntegerArray target = new AtomicIntegerArray(ARRAY_LENGTH);
		while (reps-- > 0) {
			if (arrayType == ArrayType.DIFFERENT) {
				copyToAI(targetContents, target);
			}
			for (int i=0; i < ARRAY_LENGTH; i++) {
				int x = source[i];
				if (target.get(i) != x) {
					target.set(i, x);
				}
			}
			total += target.get(rindex);
		}
		return total;
	}
	
	private static void copyToAI(int[] source, AtomicIntegerArray target) {
		assert source.length == target.length();
		for (int i=0; i<source.length; i++) {
			target.lazySet(i, source[i]);
		}
	}
	
	public static void main(String[] args) {
		Runner.main(CondWriteBench.class, args);
	}

}