OpenMP编程-数据传递

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//分配四个线程，做多线程for循环
void test2()
{const int NUMBER = 100;  int* dataA = new int[NUMBER];  int* dataB = new int[NUMBER];  for (int i= 0; i < NUMBER; i++)  {  dataA[i] = i+1;  dataB[i] = 2*(i+1);  }      long double sum = 0.0;  omp_set_num_threads(4);  
#pragma omp parallel for reduction(+:sum)  for (int i = 0; i < NUMBER;  i++)   {  sum += dataA[i] + dataB[i]; cout<<omp_get_thread_num()<<" ";}     cout<<sum<<endl;  delete [] dataA;  delete [] dataB;  
}

//为每个section分配一个线程，适用于函数
void test3()
{//分配四个线程omp_set_num_threads(4);  
#pragma omp parallel{#pragma omp sections {
#pragma omp sectionprintf("section 1 ThreadId = %d\n", omp_get_thread_num());#pragma omp sectionprintf("section 2 ThreadId = %d\n", omp_get_thread_num());#pragma omp sectionprintf("section 3 ThreadId = %d\n", omp_get_thread_num());#pragma omp sectionprintf("section 4 ThreadId = %d\n", omp_get_thread_num());}}
}

//并行内部私有，不传出。
void test4()
{int share_a = 10; // 共享变量  int share_to_private_b = 10; //通过private子句修饰该变量之后在并行区域内变为私有变量  #pragma omp parallel   {   
#pragma omp for private(share_to_private_b)   for (int i = 0; i < share_to_private_b; ++i) //该循环变量是私有的，若为两个线程，则一个线程执行0 <= i < 5，另一个线程执行5 <= i < 10  {  std::cout << i << std::endl;  }  }  
}

//并行区域内私有，不传出。
void test5()
{int share_a = 10; // 共享变量  int share_to_private_b = 10; //通过private子句修饰该变量之后在并行区域内变为私有变量  #pragma omp parallel for firstprivate(share_to_private_b)   for (int i = 0; i < 10; ++i)   {  cout<<"ID "<<omp_get_thread_num()<<"  ";std::cout << ++share_to_private_b << std::endl;  }  cout<<"share_to_private_b is :"<<share_to_private_b<<endl;}

//并行区域内私有，传出
void test6()
{int shared_to_last_private = 1;omp_set_num_threads(1);  
#pragma omp parallel for lastprivate(shared_to_last_private) firstprivate(shared_to_last_private)   for (int i = 0; i < 10; ++i)   {  std::cout << ++shared_to_last_private << std::endl;  }  std::cout << "After: " << shared_to_last_private << std::endl;  }

共享 传出void test7()
{int sum = 0;
omp_set_num_threads(4);  
#pragma omp parallel for shared(sum)   for (int i = 0; i < 10; ++i)   {  sum += i;  cout<<"ID "<<omp_get_thread_num()<<"  ";std::cout << sum << std::endl;  }  std::cout << "After: " << sum << std::endl;  
}

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