Question

Perform an experimental analysis to test and compares the relative running times of this method

[HINT: use the following inputs size to check each example (1000). You can generate each array using random number generator to fill the array with the pervious input size].

/** Returns the sum of the integers in given array. */

public static int example1(int[] arr) {

int n = arr.length, total = 0;

for (int j=0; j < n; j++) // loop from 0 to n-1

total += arr[j];

return total;

}

Answer 1

public class ArraySumTime {
        
        public static int example1(int[] arr) {
                int n = arr.length, total = 0;

                for (int j = 0; j < n; j++) // loop from 0 to n-1
                        total += arr[j];

                return total;
        }
        
        public static long findTime(int size) {
                int arr[] = new int[size];
                
                for(int i=0; i<size; i++) {
                        arr[i] = (int) (Math.random() * size);
                }
                
                long start = System.nanoTime();
                example1(arr);
                long end = System.nanoTime();
                
                return (end - start);
        }

        public static void main(String[] args) {
                
                
                for(int size=1000; size<=1000000; size *= 2) {
                        System.out.println("For Size: " + size + ", Time: " + findTime(size) + "ns.");
                }
        }

}

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The method runs a loop for N elements, Hence its time is proportional to the size of the array given.. hence If for a size of N element, code takes T seconds.. Then for size 2N, it should ideally take 2*N time.
I have coded to show how the time increases when we increase the size by a factor of 2.. However The data will keep changing in each run, because of system resources.. 


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