openMP实现的快排

#include <cstdio>
#include <ctime>
#include <omp.h>
#include <iostream>
#include <algorithm>
using namespace std;
#define N 10040000

int A[N],f[N],LC[N],RC[N],ans[N],cnt;
int n;// length of sequence
int th;// number of thread
void output(int i)
{
	if(i>=n) return;
	output(LC[i]);
	ans[cnt++]=A[i];
	output(RC[i]);
}

int main ()
{
	int i,root;
	bool flag=false;
	double f1,f2;
	int T=12;
	while(scanf("%d%d",&n,&th)!=EOF) // input the length of sequence and number of thread
	{
		cnt=0;
	//generate the original sequence
	srand(time(0));
	for(i=0;i<n;++i) A[i]=rand();

	time_t first,second;
	first=clock();

	omp_set_num_threads(th);
#pragma omp parallel private(i) shared(root)
	{
#pragma omp for 
		for(i=0;i<n;++i)
		{
			root=i;// compete to be the root of the balance tree
			LC[i]=RC[i]=n+1;
		}
#pragma omp for
		for(i=0;i<n;++i)
			f[i]=root;
	}
	
#pragma omp parallel private(i,flag) shared(A,f,LC,RC)
	{
#pragma omp for
		for(i=0;i<n;++i)
		if(i!=root)
		{
			flag=false;
			while(!flag)
			{
				if(A[i]<A[f[i]] || A[i]==A[f[i]] && i<f[i]) //go to left
				{
					if(LC[f[i]]>n)// if no left child
					{
						LC[f[i]]=i;
						flag=true;
					}
					else f[i]=LC[f[i]];
				}
				else //go to right
				{
					if(RC[f[i]]>n)// if no right child
					{
						RC[f[i]]=i;
						flag=true;
					}
					else f[i]=RC[f[i]];
				}
			}
		}
	}
	output(root); // recursively get the sorted sequence
	second=clock();
	printf("n is %d\n",n);
	printf("parallel time is %lf\n",f1=(second-first)*1.0/CLOCKS_PER_SEC);
	first=clock();
	sort(A,A+n);
	second=clock();
	printf("sequence time is %lf\n",f2=(second-first)*1.0/CLOCKS_PER_SEC);
	printf("rate is %lf\n",f2/f1);
	}
	return 0;
}