I'm writing a program to determine the size of the second-level cache line, I used the article http://igoro.com/archive/gallery-of-processor-cache-effects/. But I have completely different results. Through the Coreinfo program, I learned that the size of the first and second level strings is 64 bytes in length. While I decided to get at least the size of the first level line, but some completely inadequate results are obtained
#include "stdafx.h"
#include <time.h>
#include <iostream>
#include <string>
using namespace std;
int main()
{
int t;
const int N = 8000;
volatile int arr[N];
unsigned int A;
char ask1 = 'y';
srand(time(NULL));
while (ask1 == 'y')
{
for (int j = 0; j < N; j++)
arr[j] = rand();
for (int i = 1; i <= 64; i++)
{
A = clock();
for (int k = 0; k < 100000; k++)
for (int j = 0; j < N; j += i)
{
t = arr[j];
}
//cout << i << "\tstep, time\t" << clock() - A << '\t' << t << endl;
arr[i] = (clock() - A); //Instead of printing, so as not to destroy the cache, I decided to write the execution time in the same array, and then output it
}
for (int i = 1; i <= 64; i++)
cout << i << "\tstep, time\t" << arr[i] << endl;
cout << "Repeat?(y/n): ";
cin >> ask1;
cout << endl;
}
/**/
const int n = 1600000000;
int l;
unsigned int a;
char ask = 'y';
srand(time(NULL)); //it's just for random filling, so it's always been different, although here it's not really necessary for me
while (ask == 'y')
{
volatile int byte8[2];
for (int j = 0; j < 2; j++)
byte8[j] = rand();
a = clock();//write the time before reading array cycles
for (int k = 0; k < n / 2; k++) /*divide n by the number of
repetitions of the inner cycle, so that everywhere in
the same number of repetitions */
for (int i = 0; i < 2; i++)
l = byte8[i];
cout << size(byte8) * 4 << "\tbytes\t" << clock() - a << endl;
//output the number of ms needed for reading
// we repeat the same for arrays of longer length
volatile int byte16[4];
for (int j = 0; j < 4; j++)
byte16[j] = rand();
a = clock();
for (int k = 0; k < n / 4; k++)
for (int i = 0; i < 4; i++)
l = byte16[i];
cout << size(byte16) * 4 << "\tbytes\t" << clock() - a << endl;
volatile int byte32[8];
for (int j = 0; j < 8; j++)
byte32[j] = rand();
a = clock();
for (int k = 0; k < n / 8; k++)
for (int i = 0; i < 8; i++)
l = byte32[i];
cout << size(byte32) * 4 << "\tbytes\t" << clock() - a << endl;
/*
int byte60[15];
for (int j = 0; j < 15; j++)
byte60[j] = rand();
a = clock();
for (int k = 0; k < n / 15; k++)
for (int i = 0; i < 15; i++)
l = byte60[i];
cout << size(byte60) * 4 << "\tbytes\t" << clock() - a << endl;
*/
volatile int byte64[16];
for (int j = 0; j < 16; j++)
byte64[j] = rand();
a = clock();
for (int k = 0; k < n / 16; k++)
for (int i = 0; i < 16; i++)
l = byte64[i];
cout << size(byte64) * 4 << "\tbytes\t" << clock() - a << endl;
/*
int byte68[17];
for (int j = 0; j < 17; j++)
byte68[j] = rand();
a = clock();
for (int k = 0; k < n / 17; k++)
for (int i = 0; i < 17; i++)
l = byte68[i];
cout << size(byte68) * 4 << "\tbytes\t" << clock() - a << endl;
*/
volatile int byte96[24];
for (int j = 0; j < 24; j++)
byte96[j] = rand();
a = clock();
for (int k = 0; k < n / 24; k++)
for (int i = 0; i < 24; i++)
l = byte96[i];
cout << size(byte96) * 4 << "\tbytes\t" << clock() - a << endl;
volatile int byte128[32];
for (int j = 0; j < 32; j++)
byte128[j] = rand();
a = clock();
for (int k = 0; k < n / 32; k++)
for (int i = 0; i < 32; i++)
l = byte128[i];
cout << size(byte128) * 4 << "\tbytes\t" << clock() - a << endl;
volatile int byte192[48];
for (int j = 0; j < 48; j++)
byte192[j] = rand();
a = clock();
for (int k = 0; k < n / 48; k++)
for (int i = 0; i < 48; i++)
l = byte192[i];
cout << size(byte192) * 4 << "\tbytes\t" << clock() - a << endl;
volatile int byte256[64];
for (int j = 0; j < 64; j++)
byte256[j] = rand();
a = clock();
for (int k = 0; k < n / 64; k++)
for (int i = 0; i < 64; i++)
l = byte256[i];
cout << size(byte256) * 4 << "\tbytes\t" << clock() - a << endl;
volatile int byte512[128];
for (int j = 0; j < 128; j++)
byte512[j] = rand();
a = clock();
for (int k = 0; k < n / 128; k++)
for (int i = 0; i < 128; i++)
l = byte512[i];
cout << size(byte512) * 4 << "\tbytes\t" << clock() - a << endl;
cout << "Repeat?(y/n): ";
cin >> ask;
cout << endl;
}
system("pause");
return 0;
}
- 1 step, time 369
- 2 step, time 184
- 3 step, time 123
- 4 step, time 101
- 5 step, time 77
- 6 step, time 60
- 7 step, time 52
- 8 step, time 45
- 9 step, time 44
- 10 step, time 38
- 11 step, time 33
- 12 step, time 32
- 13 step, time 29
- 14 step, time 26
- 15 step, time 31
- 16 step, time 26
- 17 step, time 22
- 18 step, time 21
- 19 step, time 20
- 20 step, time 18
- 21 step, time 18
- 22 step, time 18
- 23 step, time 16
- 24 step, time 16
- 25 step, time 15
- 26 step, time 16
- 27 step, time 15
- 28 step, time 21
- 29 step, time 14
- 30 step, time 13
- 31 step, time 12
- 32 step, time 12
- 33 step, time 12
- 34 step, time 13
- 35 step, time 11
- 36 step, time 12
- 37 step, time 11
- 38 step, time 10
- 39 step, time 11
- 40 step, time 18
- 41 step, time 10
- 42 step, time 10
- 43 step, time 10
- 44 step, time 26
- 45 step, time 9
- 46 step, time 9
- 47 step, time 9
- 48 step, time 8
- 49 step, time 9
- 50 step, time 8
- 51 step, time 9
- 52 step, time 8
- 53 step, time 8
- 54 step, time 8
- 55 step, time 8
- 56 step, time 7
- 57 step, time 7
- 58 step, time 8
- 59 step, time 7
- 60 step, time 7
- 61 step, time 7
- 62 step, time 7
- 63 step, time 6
- 64 step, time 7
Repeat?(y/n): n
8 bytes 1227
- 16 bytes 1736
- 32 bytes 951
- 64 bytes 862
- 96 bytes 805
- 128 bytes 805
- 192 bytes 769
- 256 bytes 1232
- 512 bytes 909
Repeat?(y/n): y
8 bytes 1220
- 16 bytes 1739
- 32 bytes 944
- 64 bytes 842
- 96 bytes 815
- 128 bytes 804
- 192 bytes 781
- 256 bytes 1220
- 512 bytes 905
- Repeat?(y/n):
The point is that I can not use functions like GetLogicalProcessorInformation, I need to define a test. I launch in Visual Studio 2017 with a configuration on Release. Sorry for my English
