#include<iostream>
#include<cstdlib>
#include <thread>

using namespace std;

// maximum size of matrix
#define MAX 4

// maximum number of threads
#define MAX_THREAD 4

int matA[MAX][MAX];
int matB[MAX][MAX];
int matC[MAX][MAX];
int step_i = 0;

void* multi(void* arg)
{
	int core = step_i++;


	for (int i = core * MAX / 4; i < (core + 1) * MAX / 4; i++)
		for (int j = 0; j < MAX; j++)
			for (int k = 0; k < MAX; k++)
				matC[i][j] += matA[i][k] * matB[k][j];
}


int main()
{

	for (int i = 0; i < MAX; i++) {
		for (int j = 0; j < MAX; j++) {
			matA[i][j] = rand() % 10;
			matB[i][j] = rand() % 10;
		}
	}


	cout << endl
		<< "Matrix A" << endl;
	for (int i = 0; i < MAX; i++) {
		for (int j = 0; j < MAX; j++)
			cout << matA[i][j] << " ";
		cout << endl;
	}


	cout << endl
		<< "Matrix B" << endl;
	for (int i = 0; i < MAX; i++) {
		for (int j = 0; j < MAX; j++)
			cout << matB[i][j] << " ";
		cout << endl;
	}

	// declaring four threads
	thread(MAX_THREAD);


	// Creating four threads, each evaluating its own part
	for ( int i = 0; i < MAX_THREAD; i++) {
		thread[i] = thread(multi, i + 1);

	}

	// joining and waiting for all threads to complete
	for (int i = 0; i < MAX_THREAD; i++)
		join(thread[i],NULL);

	// Displaying the result matrix
	cout << endl
		<< "Multiplication of A and B" << endl;
	for (int i = 0; i < MAX; i++) {
		for (int j = 0; j < MAX; j++)
			cout << matC[i][j] << " ";
		cout << endl;
	}
	return 0;
}