My friend and I are stumped. In these two blocks of code, why is the first inner loop faster than the second inner loop? Is this some sort of JVM optimization?
public class Test {
public static void main(String[] args) {
int[] arr = new int[100000000];
arr[99999999] = 1;
long t1, t2, t3;
for (int ndx = 0; ndx < 10; ndx++) {
t1 = System.currentTimeMillis();
for (int i = 0; i < arr.length; i++)
if (0 < arr[i])
System.out.print("");
t2 = System.currentTimeMillis();
for (int i = 0; i < arr.length; i++)
if (arr[i] > 0)
System.out.print("");
t3 = System.currentTimeMillis();
System.out.println(t2 - t1 +" "+(t3 - t2));
}
}
}
And the results:
me@myhost ~ $ java Test
57 80
154 211
150 209
149 209
150 209
150 209
151 209
150 210
150 210
149 209
Swapped the orderings of inequalities:
public class Test {
public static void main(String[] args) {
int[] arr = new int[100000000];
arr[99999999] = 1;
long t1, t2, t3;
for (int ndx = 0; ndx < 10; ndx++) {
t1 = System.currentTimeMillis();
for (int i = 0; i < arr.length; i++)
if (arr[i] > 0)
System.out.print("");
t2 = System.currentTimeMillis();
for (int i = 0; i < arr.length; i++)
if (0 < arr[i])
System.out.print("");
t3 = System.currentTimeMillis();
System.out.println((t2 - t1) +" "+(t3 - t2));
}
}
}
And the results:
me@myhost ~ $ java Test
56 80
155 210
150 209
149 209
151 210
149 209
150 209
149 208
149 209
149 208
Insanity: doing the same thing over and over again and getting different results.