// 2.1.2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <stdlib.h>
#include <Windows.h>

#define nmax 10000

int sum;
int t[nmax];
#define threadCount 4
//Critical section
CRITICAL_SECTION cs;

DWORD WINAPI ThreadFunc(LPVOID lpdwParam) {
	int tid = (int)lpdwParam;
	int s = 0;
	int i;
	int dn = nmax / threadCount;
	int start = tid * dn;
	int stop = tid != threadCount - 1 ? (tid + 1)*dn : nmax;
	for (i = start; i<stop; i++) s += t[i];
	// Get into critical section 
	EnterCriticalSection(&cs);
	sum += s;
	// Leave critical section
	LeaveCriticalSection(&cs);
	return 0;
}

int _tmain(int argc, _TCHAR* argv[])
{
	DWORD dwThreadId, dwThrdParam[threadCount];
	HANDLE ahThreads[threadCount];

	InitializeCriticalSection(&cs);

	int i, s = 0, z = 100;
	for (i = 0; i<nmax; i++) t[i] = rand() % z;

	//sequential
	s = 0;
	int time = GetTickCount();
	for (i = 0; i<nmax; i++) s += t[i];
	std::cout << "Sequential sum: " << s << std::endl;
	time = time - GetTickCount();
	std::cout << "Sequential sum time: " << s/10000 << " ticks of clock [*10000]" <<  std::endl;
	//parallel
	sum = 0;
	time = GetTickCount();
	for (i = 0; i<threadCount; i++)
	{
		dwThrdParam[i] = i;
		ahThreads[i] = CreateThread(NULL, 0, ThreadFunc, (LPVOID)dwThrdParam[i], 0, &dwThreadId);
	}
	for (i = 0; i<threadCount; i++)
	{
		WaitForMultipleObjects(threadCount, ahThreads, true, INFINITE);
	}
	time = time - GetTickCount();
	std::cout << std::endl;

	std::cout << "Parallel sum: " << sum << std::endl;
	std::cout << "Parallel sum time: " << s / 10000 << " ticks of clock [*10000]" << std::endl;
	DeleteCriticalSection(&cs);
	std::cin.ignore(2);
	return 0;
}