Openmp编程练习
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火车卖票
// OpenMP2.cpp : 定义控制台应用程序的入口点。
//
#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);
#pragma omp atomic
num--;
//omp_unset_nest_lock(&lock);
return num+1;
}
void chushou(int i)
{
int s = getnum();
while (s >= 0)
{
omp_set_lock(&lock);
printf("站点%d卖掉了第%d张票
", i, s);
s = getnum();
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
", 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
", 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
", 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
", 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
",i, temp_sum);
for (j = 0; j <= 4; j++)
{
temp_sum += a[i][j];
}
printf("temp_sum is %d
", temp_sum);
increase(temp_sum);
}
printf("%d
", 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
", sum);
}
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