Averaging Primes

//Runs on Windows 7 Ultimate.

#include <vector>
bool isPrime(int number) //This is pure CSStudent.jpg but whatever
{
     int i;
     for (i=2; i<number; i++)
     { if(number % i==0)
       return false;
     }
     return true;
}

long int average(FILE* file,std::vector<float>& arr, size_t size)
{
    void *mem = malloc((sizeof(float)*4)+15); //needed to have 16 bit alligned space for the unload.
    void *ptr = (void*)(((uintptr_t)mem+15) & ~ (uintptr_t)0x0F);
    float* avgFloats=(float*)ptr;


    __m128 tot = _mm_setr_ps((float)size,(float)size,(float)size,(float)size);
    __m128 avg = _mm_setr_ps(0.0f,0.0f,0.0f,0.0f);
    long int start =__rdtsc();
    for (size_t i = 0; i < size; i=i+4)
    {
        __m128 values = _mm_loadu_ps(&arr[i]);
        __m128 div = _mm_div_ps(values,tot);
        avg = _mm_add_ps(avg,div);
    }

    _mm_store_ps (avgFloats, avg);
    float result=0;
    for (int i = 0; i < 4; i++)
    {
        result+=avgFloats[i];
    }
    long int end =__rdtsc();
    fprintf(file,"R:%f\t", result);
    return end-start;
}

int main(){
    std::vector<float> arr;
    for (size_t i = 0; i < 100000; i++) //Because of the CSStudent.jpg isPrime function I reduced this.
    {
        if (isPrime(i))
        {
            arr.push_back((float)i);
        }
    }
    size_t oldSize=arr.size();
    printf("Number of integers:%d\n",oldSize);
    size_t unalign = arr.size()%4;
    arr.resize(arr.size()+(4-unalign),0);
    FILE* file= fopen("output.txt","w");
    for (int i = 0; i < 100; i++)
    {

        fprintf(file,"Run#%02d: %ld\n",i,average(file,arr,oldSize));
    }

    getchar();
    return 0;
}
//Using my i7-3720QM. Has had issues..
//Time gotten using _rdtsc()
//Only measured the actual process of averaging and recombining the value
//output.txt:
R:47362.574219  Run#00: 13630
R:47362.574219  Run#01: 12560
R:47362.574219  Run#02: 12558
R:47362.574219  Run#03: 12556
R:47362.574219  Run#04: 12524
R:47362.574219  Run#05: 12526
R:47362.574219  Run#06: 12562
R:47362.574219  Run#07: 12520
R:47362.574219  Run#08: 12524
R:47362.574219  Run#09: 12520
R:47362.574219  Run#10: 12520
R:47362.574219  Run#11: 12520
R:47362.574219  Run#12: 12518
R:47362.574219  Run#13: 12524
R:47362.574219  Run#14: 12532
R:47362.574219  Run#15: 12522
R:47362.574219  Run#16: 12556
R:47362.574219  Run#17: 12526
R:47362.574219  Run#18: 12526
R:47362.574219  Run#19: 12516
R:47362.574219  Run#20: 12522
R:47362.574219  Run#21: 12518
R:47362.574219  Run#22: 12520
R:47362.574219  Run#23: 12524
R:47362.574219  Run#24: 12558
R:47362.574219  Run#25: 12522
R:47362.574219  Run#26: 12520
R:47362.574219  Run#27: 12550
R:47362.574219  Run#28: 12522
R:47362.574219  Run#29: 12524
R:47362.574219  Run#30: 12556
R:47362.574219  Run#31: 12520
R:47362.574219  Run#32: 12516
R:47362.574219  Run#33: 12522
R:47362.574219  Run#34: 12518
R:47362.574219  Run#35: 12562
R:47362.574219  Run#36: 12522
R:47362.574219  Run#37: 12524
R:47362.574219  Run#38: 12518
R:47362.574219  Run#39: 12524
R:47362.574219  Run#40: 12556
R:47362.574219  Run#41: 12550
R:47362.574219  Run#42: 12560
R:47362.574219  Run#43: 12526
R:47362.574219  Run#44: 12520
R:47362.574219  Run#45: 12526
R:47362.574219  Run#46: 12562
R:47362.574219  Run#47: 12520
R:47362.574219  Run#48: 12522
R:47362.574219  Run#49: 12526
R:47362.574219  Run#50: 12524
R:47362.574219  Run#51: 12550
R:47362.574219  Run#52: 12520
R:47362.574219  Run#53: 12520
R:47362.574219  Run#54: 12532
R:47362.574219  Run#55: 12524
R:47362.574219  Run#56: 12518
R:47362.574219  Run#57: 12532
R:47362.574219  Run#58: 12524
R:47362.574219  Run#59: 12522
R:47362.574219  Run#60: 12556
R:47362.574219  Run#61: 12552
R:47362.574219  Run#62: 12520
R:47362.574219  Run#63: 12520
R:47362.574219  Run#64: 12554
R:47362.574219  Run#65: 12526
R:47362.574219  Run#66: 12520
R:47362.574219  Run#67: 12558
R:47362.574219  Run#68: 12520
R:47362.574219  Run#69: 12554
R:47362.574219  Run#70: 12524
R:47362.574219  Run#71: 12522
R:47362.574219  Run#72: 12520
R:47362.574219  Run#73: 12526
R:47362.574219  Run#74: 12518
R:47362.574219  Run#75: 12528
R:47362.574219  Run#76: 12526
R:47362.574219  Run#77: 12526
R:47362.574219  Run#78: 12520
R:47362.574219  Run#79: 12522
R:47362.574219  Run#80: 12524
R:47362.574219  Run#81: 12524
R:47362.574219  Run#82: 12518
R:47362.574219  Run#83: 15370
R:47362.574219  Run#84: 14672
R:47362.574219  Run#85: 12562
R:47362.574219  Run#86: 12526
R:47362.574219  Run#87: 12524
R:47362.574219  Run#88: 12556
R:47362.574219  Run#89: 12520
R:47362.574219  Run#90: 12526
R:47362.574219  Run#91: 12618
R:47362.574219  Run#92: 12622
R:47362.574219  Run#93: 12522
R:47362.574219  Run#94: 12526
R:47362.574219  Run#95: 12522
R:47362.574219  Run#96: 12526
R:47362.574219  Run#97: 12518
R:47362.574219  Run#98: 12556
R:47362.574219  Run#99: 12554