I have the following program. I was just kind of messing around with other stuff when I noticed something unusual. The line "y = 3;" seems to have an effect on how fast the previous block of code can be run. When the line is commented out, the first half of the code runs around ten times slower than the second half. However, when the line is uncommented, both halves run at the same speed. Interestingly, the line in question should not be doing anything, as at that point the value of y is already 3.
EDIT: I added line "System.out.println(y)" right above "y=3" and it prints 3. That's why I think it's 3. And I'm measuring based on the output of the program. The two lines that it prints are the two runtimes, and the Timer code at the bottom shows clearly how I am measuring time.
/**
* @author lpreams
*/
public class Misc {
public static void main(String[] args) {
new Misc().run();
}
public void run() {
Timer t = new Timer();
t.start();
int y = Integer.MIN_VALUE;
for (int j = 0; j < Integer.MAX_VALUE; ++j) {
for (int i = 0; i < Integer.MAX_VALUE; ++i) {
++y;
}
}
t.stop();
System.out.println(t.getElapsedTime());
t.reset();
//y = 3;
t.start();
for (int j = 0; j < Integer.MAX_VALUE; ++j) {
for (int i = 0; i < Integer.MAX_VALUE; ++i) {
++y;
}
}
t.stop();
System.out.println(t.getElapsedTime());
}
private static class Timer {
private long startTime = 0;
private long stopTime = 0;
private long elapsed = 0;
public void start() {
this.startTime = System.nanoTime()/1000000;
}
public void stop() {
this.stopTime = System.nanoTime()/1000000;
elapsed += stopTime - startTime;
}
public long getElapsedTime() {
return elapsed;
}
public void reset() {
elapsed = 0;
}
}
}
I am running this code in Eclipse on OS X 10.9.2. I am running the latest version of java. My machine is a MacBook Pro with a 2.4ghz Core 2 Duo with 8gb of RAM.
