Question

(Using Java)

I’m testing sorting arrays to see literally how fast different sorting arrays take. I want to weed out the erroneous times, so ideally I would like to start a timer, run the sort in a loop of say 100 times, stop the timer, then divide by 100 to get a pretty accurate measure.

The problem is if I were to loop the same array, it’ll sort properly the first time, then each sort after, it’ll keep sorting the already sorted array, which isn’t what I want.

Maybe I’m missing an obvious solution, but is there any way I can make it keep sorting the same initial randomized array?

I thought about reassigning the newly sorted array back to the initial random array each time, but that would mess up my timer..

thanks for any suggestions

what i would like to do:

        startTime = System.nanoTime();
        for(int i=0; i<cntr; i++) {
            sort array
        }
        endTime = System.nanoTime();
        time = (endTime - startTime)/cntr;

Answer 1

You can make a copy before you start sorting, and then copy from that stored copy into the array being sorted in each iteration of the loop.

int[] toBeSorted = new int[10000];
// fill the array with data
int[] copied = new int[10000];
System.arrayCopy(toBeSorted, 0, copied, 0, copied.length);
// prepare the timer, but do not start it
for (int = 0 ; i != 100 ; i++) {
    System.arrayCopy(copied, 0, toBeSorted, 0, copied.length);
    // Now the toBeSorted is in its initial state
    // Start the timer
    Arrays.sort(toBeSorted);
    // Stop the timer before the next iteration
}