cache line

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

int SIZE = 1024 * 1024 * 1024;
int CLSIZE = 64;

void test(char *a, int step) {
    clock_t start = clock();

    for (int i = 0; i < SIZE; i += step) {
        a[i] *= 2;
    }

    clock_t end = clock();
    float ms = (float)(end - start) / (CLOCKS_PER_SEC / 1000);
    printf("Step = %d: %f ms\n", step, ms);
}

void main() {
    char *aaa = (char *)malloc(SIZE);
    test(aaa, 4);
    test(aaa, 64);
}

// $ gcc cache_line.c -std=c99 -O0 -o cache_line && ./cache_line
// Step = 4: 813.681030 ms
// Step = 64: 110.019997 ms