#include <iostream>
#include <math.h>

// C = A * B
static void mult(int n, double * c, double const * a, double const * b) {
	int in = 0;
	for (int i = 0; i < n; ++ i, in += n) {
		int inn = in + n;
		for (int j = 0; j < n; ++ j) {
			int kj = j;
			double cc = 0;
			for (int ik = in; ik < inn; ++ ik, kj += n)
				cc += a[ik] * b[kj];
			c[in + j] = cc;
		}
	}      
}

 // C += A
static void add(int n, double * c, double const * a) {
	int nn = n * n;
	for (int i = 0; i < nn; i++)
		c[i] += a[i];
}

static void init(int n, double * m, int a, int b, double scale) {
	for (int i = 0; i < n; ++ i)
		for (int j = 0; j < n; ++ j)
			m[i * n + j] = (a * i + b * j) / scale;
}

int main () {
	int N = 200;
	int M = 100;
	double a [N*N];
	double b [N*N];
	double c [N*N];
	
	init(N, a, 3, 1, 300);
	init(N, b, 2, 7, 300);
		
	double start = clock() * 1000.0 / CLOCKS_PER_SEC;
	for (int i = 0; i < M; i++) {
		mult(N, c, a, b);
		add(N, c, a);
		add(N, c, b);
	}
	double end = clock() * 1000.0 / CLOCKS_PER_SEC;
	if (fabs(c[N*N-1] - 2487.5) > 1e10)
		std::cout << "wrong answer" << std::endl;
	std::cout << ((end - start) / M) << std::endl << std::endl;

	init(N, a, 3, 1, 300);
	init(N, b, 2, 7, 300);
	
	start = clock() * 1000.0 / CLOCKS_PER_SEC;
	for (int i = 0; i < M; i++) {
		mult(N, c, a, b);
		add(N, c, a);
		add(N, c, b);
	}
	end = clock() * 1000.0 / CLOCKS_PER_SEC;
	if (fabs(c[N*N-1] - 2487.5) > 1e10)
		std::cout << "wrong answer" << std::endl;
	std::cout << ((end - start) / M) << std::endl << std::endl;
	return 0;
}