How to calculate time complexity of matrix multiplication, if the matrix size is 2000?

Question

I need to calculate the time complexity of matrix multiplication, the size of the matrices is 2000, but when I run the program, doesn't print anything. The program works fine when I change the size to 200. Basically, I just need to calculate the time that it takes to multiply matrices for n = 500, 1000, 1500, 2000. I've read that if you have a matrix with a big size, you should declare it as global, I've tried that but it's the same.

This is the main file:

#include <iostream>
#include <time.h>
#include "matrices.h"

using namespace std;
int size = 2000;

int** mat1;
int** mat2;
int** mat3;

int main(int argc, char** argv) {

 //int** mat1;
 mat = new int* [size];
 //int** mat2;
 mat2 = new int* [size];
 //int** mat3;
 mat3 = new int* [size];

int step = 500; 
double ticksPerMs = double{ CLOCKS_PER_SEC } / 1000;
clock_t startTime = clock();

for (int i = 0; i < size; i++) {
    for (int j = 0; j < size; j++) {
        mat1[i] = new int[size];
    }
}

for (int i = 0; i < size; i++) {
    for (int j = 0; j < size; j++) {
        mat2[i] = new int[size];
    }
}

for (int i = 0; i < size; i++) {
    for (int j = 0; j < size; j++) {
        mat3[i] = new int[size];
    }
}

for (int n = 0; n <= size; n += step) {
    for (int i = 0; i < size; i++) {
        for (int j = 0; j < size; j++) {
            mat1[i][j] = n - i;
            mat2[i][j] = n - i;
            mat3[i][j] = 0;
          
        }
    }
    matMult1(mat1, mat2, mat3, n);
    double durationMs = (clock() - startTime) / ticksPerMs;
    cout << "Step: " << n << endl;
    cout << "Matrix Multiplication 1: " << durationMs << endl;   
}

for (int n = 0; n <= size; n += step) {
    for (int i = 0; i < size; i++) {
        for (int j = 0; j < size; j++) {
            mat1[i][j] = n - i;
            mat2[i][j] = n - i;
            mat3[i][j] = 0;

        }
    }
    matMult2(mat1, mat2, mat3, n);
    double durationMs = (clock() - startTime) / ticksPerMs;
    cout << "Step: " << n << endl;
    cout << "Matrix Multiplication 2: " << durationMs << endl;
}

for (int n = 0; n <= size; n += step) {
    for (int i = 0; i < size; i++) {
        for (int j = 0; j < size; j++) {
            mat1[i][j] = n - i;
            mat2[i][j] = n - i;
            mat3[i][j] = 0;

        }
    }
    matMult3(mat1, mat2, mat3, n);
    double durationMs = (clock() - startTime) / ticksPerMs;
    cout << "Step: " << n << endl;
    cout << "Matrix Multiplication 3: " << durationMs << endl;
}
return 0;

}

And this is the header file:

#ifndef _MATRIX_H
#define _MATRIX_H


void matMult1(int **a, int **b, int **c, int n);
void matMult2(int **a, int **b, int **c, int n);

void transpone(int **a, int n);
void matMult3(int **a, int **b, int **c, int n);

void matMult1(int **a, int **b, int **c, int n)
{
for(int i=0; i<n; i++)
for(int j=0; j<n; j++) {
int sum =0;
for(int k=0; k<n; k++)
sum += a[i][k] * b[k][j];
  c[i][j]= sum;  
  
    }    
}

void matMult2(int **a, int **b, int **c, int n)
{
for(int i=0; i<n; i++)
for(int j=0; j<n; j++)
c[i][j] = 0; 
for(int i=0; i<n; i++)
  for(int j=0; j<n; j++)
    for(int k=0; k<n; k++) {
      c[i][j] += a[i][k] * b[k][j];
    }             
}

void transpone(int **a, int n)
{
int tmp;
for(int i=0; i<n; i++)
  for(int j=i+1; j<n; j++) {
    tmp = a[i][j];
    a[i][j] = a[j][i];
    a[j][i] = tmp;
  }    
}

void matMult3(int **a, int **b, int **c, int n)
{
int sum;
for(int i=0; i<n; i++)
  for(int j=0; j<n; j++)
    c[i][j] = 0; 

transpone(b, n);
for(int i=0; i<n; i++)
    for(int j=0; j<n; j++) {
      sum = 0;
      for(int k=0; k<n; k++) 
        sum += a[i][k] * b[j][k];
      c[i][j] = sum;
    }           
}
#endif