begin = omp_get_wtime();

        #pragma omp parallel for reduction(+:sum_distribution)
        for (int i = 0; i < x.n; ++i) {
            int example = dist2[i].second;
            float d2 = 0.0, diff;
            for (int j = 0; j < x.d; ++j) {
                diff = x(example,j) - x(chosen_pts[ndx - 1],j);
                d2 += diff * diff;
            }
            if (d2 < dist2[i].first) {
                dist2[i].first = d2;
            }

            sum_distribution += dist2[i].first;
        }
        end = omp_get_wtime() - begin;

        std::cout << "center assigning -- "
                << ndx << " of " << k << " = "
                << (float)ndx / k * 100
                << "% is done. Elasped time: "<< (float)end <<"\n";
/*
without pragma
center assigning -- 1 of 5000 = 0.02% is done. Elasped time: 1.9931
center assigning -- 2 of 5000 = 0.04% is done. Elasped time: 2.35191
center assigning -- 3 of 5000 = 0.06% is done. Elasped time: 2.24706
center assigning -- 4 of 5000 = 0.08% is done. Elasped time: 2.24564
center assigning -- 5 of 5000 = 0.1% is done. Elasped time: 2.38944
center assigning -- 6 of 5000 = 0.12% is done. Elasped time: 2.10984
center assigning -- 7 of 5000 = 0.14% is done. Elasped time: 2.14609
center assigning -- 8 of 5000 = 0.16% is done. Elasped time: 2.13032
center assigning -- 9 of 5000 = 0.18% is done. Elasped time: 2.09305
center assigning -- 10 of 5000 = 0.2% is done. Elasped time: 2.66016
center assigning -- 11 of 5000 = 0.22% is done. Elasped time: 2.08289
center assigning -- 12 of 5000 = 0.24% is done. Elasped time: 2.09065
center assigning -- 13 of 5000 = 0.26% is done. Elasped time: 2.08595
center assigning -- 14 of 5000 = 0.28% is done. Elasped time: 2.10572
center assigning -- 15 of 5000 = 0.3% is done. Elasped time: 2.05595
center assigning -- 16 of 5000 = 0.32% is done. Elasped time: 2.06249
...keeps running...

with pragma
center assigning -- 1 of 5000 = 0.02% is done. Elasped time: 0.707227
center assigning -- 2 of 5000 = 0.04% is done. Elasped time: 0.721848
center assigning -- 3 of 5000 = 0.06% is done. Elasped time: 0.755143
center assigning -- 4 of 5000 = 0.08% is done. Elasped time: 0.708477
center assigning -- 5 of 5000 = 0.1% is done. Elasped time: 0.659136
center assigning -- 6 of 5000 = 0.12% is done. Elasped time: 0.678935
center assigning -- 7 of 5000 = 0.14% is done. Elasped time: 0.662681
center assigning -- 8 of 5000 = 0.16% is done. Elasped time: 0.65667
--- stops here ---

*/