/*
 *
 * $g++ -O3 -msse2 sseex1.c
 * $./a.out 51200 
 * */

#include<stdio.h>
#include<emmintrin.h>
#include<math.h>
void normal(float* a, int N){
    for (int i = 0; i < N; ++i) a[i] = sqrt(a[i]); 
} 
void sse(float* a, int N){   
    int nb_iters = N / 4;//N is multiple of 4
    __m128* ptr = (__m128*)a;
    for (int i = 0; i < nb_iters; ++i, ++ptr, a += 4)
	_mm_store_ps(a, _mm_sqrt_ps(*ptr));
}                                                                                                                                                                                                                
int main(int argc, char** argv){                                                                                                                                                                                                                
    if (argc != 2) return 1; 
    int N = atoi(argv[1]);
    float* a;
    posix_memalign((void**)&a, 16,  N * sizeof(float)); 
    system("date");
    for (int i = 0; i < N; ++i) a[i] = 3141592.65358; 
	for (int i = 0; i < N; ++i) normal(a, N);
    system("date");
   for (int i = 0; i < N; ++i)	a[i] = 3141592.65358;
	for (int i = 0; i < N; ++i) sse(a, N); 
    system("date");
}