Cache illustration

cachecache.c

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

#define N 2000
#define M 1000

int t[M][M] = {{0}};

int main(){
	for (int i = 0; i < N; i++)
		// swap the two lines to observe the effect
		for (int j = 0; j < M; j++)
			for (int k = 0; k < M; k++){
				// printf("t[%d][%d] @ %p\n", j, k, &(t[j][k]));
				t[j][k] = k + j;
			}
	return EXIT_SUCCESS;
}

gcc -g -O3 -o cachecache cachcecahe.c

Results:

• 24.7% cache miss versus 99.9% cache miss
• 3.113s versus 26.991s