Test whether using arma::max function is faster than using loops.

test.cpp

#include <iostream>
#include <vector>
#include <ctime>
#include <armadillo>

using namespace std;
using namespace arma;

int main() {
    mat A = randu<mat>(10000,10000);
    mat B = randu<mat>(10000,10000);
    vector<vector<int> > C(10000, vector<int>(10000, 1));
    vector<vector<int> > D(10000, vector<int>(10000, 2));

    clock_t t1;
    t1 = clock();

    A = arma::max(A, B);

    t1 = clock() - t1;
    double time_taken1 = ((double)t1) / CLOCKS_PER_SEC;

    clock_t t2;
    t2 = clock();

    for (int i = 0; i < 10000; ++i)
        for (int j = 0; j < 10000; ++j)
            if (C[i][j] < D[i][j])
                C[i][j] = D[i][j];

    t2 = clock() - t2;
    double time_taken2 = ((double)t2) / CLOCKS_PER_SEC;

    cout << "arma::max took " << time_taken1 << " seconds" << endl;
    cout << "Iterating loops took " << time_taken2 << " seconds" << endl;

    if (time_taken1 < time_taken2)
        cout << "arma::max is faster than loops by "
             << ((time_taken2 - time_taken1) / time_taken1) * 100 << " %" << endl;
    else
        cout << "Using loops is faster than arma::max by  "
             << ((time_taken1 - time_taken2) / time_taken2) * 100 << " %" << endl;

    return 0;
}