#include<ctime>
#include<cmath>
#include<iostream>
#include <boost/random.hpp>
 
#define PI 3.1416
 
using namespace std;
using namespace boost;
 
inline double unif_rand(){  //生成(0,1)的实数均匀分布
	//rand();
	return(rand()+0.5)/(RAND_MAX+1.0);
};
 
inline int unif_int(int a, int b){   //生成a到b-1的整数均匀分布
	return int(floor(a+(b-a)*unif_rand()));
};
 
inline double gaussien(){  //标准正态分布的生成
	return sqrt(-2.0*log(  unif_rand()  ) )*cos(  2.0*PI*unif_rand()  );
};
void main(){
	srand(static_cast<unsigned int>(time(0)));
        rand();//因为第一次的随机值不好，我们不要
	uniform_int<> distribution(1,100);
	mt19937 engine;
	mt19937::result_type random_seed= static_cast<mt19937::result_type>(time(0));
	engine.seed(random_seed);
	engine.seed(static_cast<mt19937::result_type>(random_seed));
	variate_generator<mt19937, uniform_int<> > random_choice (engine, distribution);
	normal_distribution<> normal(0,1);
	variate_generator<mt19937, normal_distribution<> > gaussian(engine,normal);
 
 
	ofstream flux("test.txt");
	//flux.precision(5);
	int N=1000000;
	flux<<"N = "<<N<<endl;
	double start, finish, duration;
	start=clock();
	for(int i=0;i<N;i++){
		random_choice();
	}
	finish=clock();
	duration=(double)(finish-start);
	flux<<"boost的uniform_int(1,100)需要"<<duration<<"毫秒..."<<endl<<endl;
 
	start=clock();
	for(int i=0;i<N;i++){
		unif_int(1,101);
	}
	finish=clock();
	duration=(double)(finish-start);
	flux<<"自己的unif_int(1,100)需要"<<duration<<"毫秒..."<<endl<<endl;
 
	start=clock();
	for(int i=0;i<N;i++){
		gaussian();
	}
	finish=clock();
	duration=(double)(finish-start);
	flux<<"boost的标准正态分布需要"<<duration<<"毫秒..."<<endl<<endl;
 
	start=clock();
	for(int i=0;i<N;i++){
		gaussien();
	}
	finish=clock();
	duration=(double)(finish-start);
	flux<<"自己的标准正态分布需要"<<duration<<"毫秒..."<<endl<<endl;
 
	flux.close ();
}