1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39

#include <iostream>
#include <Eigen/Core>
#include <ctime>
using namespace Eigen;
using namespace std;
#define MATRIX_SIZE 2000
int main()
{
    int n_a_rows = 4000;
    int n_a_cols = 3000;
    int n_b_rows = n_a_cols;
    int n_b_cols = 200;
    MatrixXi a(n_a_rows, n_a_cols);
    for (int i = 0; i < n_a_rows; ++i)
        for (int j = 0; j < n_a_cols; ++j) {
            a(i, j) = n_a_cols * i + j;
        }
    MatrixXi b(n_b_rows, n_b_cols);
    for (int i = 0; i < n_b_rows; ++i)
        for (int j = 0; j < n_b_cols; ++j) {
            b(i, j) = n_b_cols * i + j;
        }
    MatrixXi d(n_a_rows, n_b_cols);
    clock_t begin = clock();
    d = a * b;
    clock_t end = clock();
    double elapsed_secs = double(end - begin) / CLOCKS_PER_SEC;
    std::cout << "* Time taken : " << elapsed_secs << std::endl;
}

1

* Time taken : 0.782