C pow vs shift

main.c

#include <stdio.h>
#include <stdlib.h>

#include <math.h>
#include <unistd.h>
#include <time.h>

int main() {

    const size_t nTests = 10000000;
    const size_t nExp = 10000;
    int e[nExp]; 
    /* Make an array of random exponents to use in tests. */
    srand( (unsigned int)time(NULL) );
    for( int i = 0; i < nExp; i++ ) e[i] = rand() % 31;

	int sumPow = 0;
	int sumShift = 0;
	clock_t startPOW = clock(), diffPOW;
	for(int i = 0; i < nTests; i++) {
		int y = (int)pow(2,(double)e[i%nExp]);
		sumPow += y;
	}
	diffPOW = clock() - startPOW;

	clock_t startS = clock(), diffS;
	for(int i = 0; i < nTests; i++) {
		int y = 1ULL << e[i%nExp];
		sumShift += y;
	}
	diffS = clock() - startS;

	int msecPOW = diffPOW * 1000 / CLOCKS_PER_SEC;
	int msecS = diffS * 1000 / CLOCKS_PER_SEC;

	printf("Tests pow VS shift\n");
	printf("10 000 000 perform...\n");
	printf("...\n");
	printf("Sum pow:%d\n", sumPow);
	printf("Sum shift:%d\n", sumShift);
	printf("Time taken by pow %d milliseconds\n", msecPOW%1000);
	printf("Time taken by shift %d milliseconds\n", msecS%1000);
	printf("Time ratio of pow versus shift: %ju\n", diffPOW/diffS);

	return 0;
}