OpenMp之reduction求和

// OpenMP1.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include"omp.h"
#include
#include
#include
using namespace std;

#define NUM_THREADS 4
int _tmain(int argc, _TCHAR* argv[])
	{
	 omp_set_num_threads(NUM_THREADS);
	 long long sum=0;
	 clock_t time_begin =clock();
	#pragma omp parallel for reduction(+:sum)
		 
         for(long i=1;i<=1000000000;i++)
			  {
			   sum+=i;
			  }
			
		 

	  clock_t time_end=clock();
	  double s1=time_end-time_begin; 
	  cout<<"Sum="<