Openmp编程练习

火车卖票

#include "stdio.h"
#include "omp.h"
#include <windows.h>    //使用Sleep()函数需要包含此头文件

int num;
omp_lock_t lock;
int getnum()
{
	int temp = num;
	//omp_set_nest_lock(&lock);
	num--;
	//omp_unset_nest_lock(&lock);
	return num + 1;
}

void chushou(int i)
{

	int s = 1;
	while (s >= 0)
	{
		omp_set_lock(&lock);
		s = getnum();
		printf("站点%d卖掉了第%d张票\n", i, s);
		omp_unset_lock(&lock);
		Sleep(500);
	}

}
int main()
{
	num = 100;
	int myid;
	omp_init_lock(&lock);
#pragma omp parallel private(myid) num_threads(4)

	{
		myid = omp_get_thread_num();
		//printf("my id is:%d\n", myid);
		chushou(myid);
	}
	omp_destroy_lock(&lock);

	return 0;
}

生产消费循环队列

#include "stdio.h"
#include "omp.h"
#include <windows.h>    //使用Sleep()函数需要包含此头文件

int buf[5];//缓冲区的大小
int poi;
int poi2;
int num;
omp_lock_t lock;

void shengchan()
{
	puts("shengchan");
	while (true)
	{
		omp_set_lock(&lock);
		if (num < 5)
		{
			while (buf[poi] == 1)poi = (poi + 1) % 5;
			printf("生产者在%d位置上放置了一个\n", poi);
			buf[poi] = 1;
			num++;
			poi = (poi + 1) % 5;
		}
		omp_unset_lock(&lock);
		Sleep(500);
	}
}

void xiaofei()
{
	puts("xiaofei");
	while (true)
	{
		omp_set_lock(&lock);
		//printf("%d\n", num);
		if (num>=1)
		{

			while (buf[poi2] == 0)poi2 = (poi2 + 1) % 5;

			printf("消费者在%d位置上消费了一个\n", poi2);
			buf[poi2] = 0;
			num--;

		}
		omp_unset_lock(&lock);
		Sleep(500);
	}
}
int main()
{
	omp_init_lock(&lock);
#pragma omp parallel sections num_threads(2)
	{
#pragma omp section
		shengchan();
#pragma omp section
		xiaofei();
	}
	omp_destroy_lock(&lock);
	return 0;
}

蒙特卡洛圆周率

#include "stdio.h"
#include "omp.h"
#include <windows.h>    //使用Sleep()函数需要包含此头文件
#include<time.h>
#include<iostream>

using namespace std;
double distance(double x, double y)
{
	return sqrt((x - 0.5) * (x - 0.5) + (y - 0.5) * (y - 0.5));
}

bool judge(double x,double y)
{
	return distance(x, y) <= 0.5;
}
int in_num;

int main()
{
	/*
	for (int i = 1; i <= 5; i++)
	{
		cout << rand() / (double)RAND_MAX << endl;
	}*/

	bool flag = false;
	double x;
	double y;
#pragma omp for private(flag,x,y)
	for (int i = 1; i <= 10000; i++)
	{
		x = rand() / (double)RAND_MAX;
		y = rand() / (double)RAND_MAX;
		flag = judge(x,y);
		if (flag)
		{
#pragma omp atomic
			in_num++;
		}

	}
	double ans = (double)in_num / 10000;
	cout << ans*4 << endl;

}

多线程二维数组和解法1 firstprivate+atomic

#include "stdio.h"
#include "omp.h"
#include <windows.h>    //使用Sleep()函数需要包含此头文件
#include<time.h>
#include<iostream>

using namespace std;
int a[5][5] = { {1,1,1,1,1},{2,2,2,2,2},{3,3,3,3,3},{4,4,4,4,4},{5,5,5,5,5} };
int final_ans = 0;
void increase(int temp_sum)
{
#pragma omp atomic
	final_ans += temp_sum;
}
int main()
{
	int temp_sum=0;
	int i,j;
#pragma omp parallel for private(i,j) firstprivate(temp_sum) num_threads(5)//每个线程必须一致,或者采用ppt上的例子进行划分
	// firstprivate(temp_sum) reduction(+:temp_sum) 这两个不能同时出现
	for (i = 0; i <= 4; i++)
	{
		//temp_sum += 1;
		//printf("%d 当前的temp_sum值为%d\n",i, temp_sum);
		for (j = 0; j <= 4; j++)
		{
			temp_sum += a[i][j];
		}
		printf("temp_sum is %d\n", temp_sum);
		increase(temp_sum);

	}
	printf("%d\n", final_ans);
	return 0;
}

多线程二维数组解法2 线程可以不用对应数量

#include "stdio.h"
#include "omp.h"
#include <windows.h>    //使用Sleep()函数需要包含此头文件
#include<time.h>
#include<iostream>

using namespace std;
int a[5][5] = { {1,1,1,1,1},{2,2,2,2,2},{3,3,3,3,3},{4,4,4,4,4},{5,5,5,5,5} };
int ans_buf[5];
int main()
{
	int i, j;
#pragma omp parallel for num_threads(3) private(j)
	for (int i = 0; i <= 4; i++)
	{
		for (int j = 0; j <= 4; j++)
		{
			ans_buf[i] += a[i][j];
		}
	}
	int sum = 0;
	for (int i = 0; i <= 4; i++)
		sum += ans_buf[i];
	printf("%d\n", sum);
}