OpenMP将一个函数的执行分配给一个线程？

Question

基本上我需要主线程继续根据一些全局变量的值进行一些操作，这些全局变量可以由辅助线程编辑（在某些选定的时间间隔）。是这样的：

vector<int> mySharedVar; 

void secondaryThreadFunction() { 
    Do some operations 
    And update mySharedVar if necessarily 
} 

int main() { 
int count = 0; 
while(true) { 
    count++; 

    if (count%100) { //> Each 100 iterations run a parallel thraed 
     //> RUN secondaryThreadFunction in a separateThread 
    } 

    this is the main thread that based its operation on mySharedVar 
} 
} 

这是OpenMP的命令与secondaryThreadFunction();运行单个并行线程？

是否有比这任何其他更好的办法：

#pragma omp parallel num_threads(2) 
    { 
     int i = omp_get_thread_num(); 

     if (i == 0){ 
      mainThread(); 
     } 
     if (i == 1 || omp_get_num_threads() != 2){ 
      secondaryThreadFunction(); 
     } 
    } 

Answer 1

这里是我想出了：

#include <omp.h> 
#include <unistd.h> 
#include <vector> 
#include <iostream> 

std::vector<int> mySharedVar(10); 

void secondaryThreadFunction() { 
    mySharedVar[5]++; 
} 

int main() { 
    int i = 0 ; 

#pragma omp parallel sections shared(mySharedVar) private(i) 
    { 
#pragma omp section 
    //main thread 
    { 
     while(mySharedVar[5] < 10) { 
     std::cout << "main: "; 
     for(i=0; i < mySharedVar.size(); ++i){ 
      std::cout << mySharedVar[i] << " "; 
     } 
     std::cout << std::endl; 
     usleep(1.e5); // wait 0.1 seconds 
     } 
    } 
#pragma omp section 
    { 
     while(mySharedVar[5] < 10) { 
     secondaryThreadFunction(); 
     usleep(3.e5); // wait 0.3 seconds 
     } 
    } 
    } 
} 

编译和运行g++ -fopenmp test_omp_01.cc && ./a.out

输出：

main: 0 0 0 0 0 1 0 0 0 0 
main: 0 0 0 0 0 1 0 0 0 0 
main: 0 0 0 0 0 1 0 0 0 0 
main: 0 0 0 0 0 2 0 0 0 0 
main: 0 0 0 0 0 2 0 0 0 0 
main: 0 0 0 0 0 2 0 0 0 0 
main: 0 0 0 0 0 3 0 0 0 0 
main: 0 0 0 0 0 3 0 0 0 0 
main: 0 0 0 0 0 3 0 0 0 0 
main: 0 0 0 0 0 4 0 0 0 0 
main: 0 0 0 0 0 4 0 0 0 0 
main: 0 0 0 0 0 4 0 0 0 0 
main: 0 0 0 0 0 5 0 0 0 0 
main: 0 0 0 0 0 5 0 0 0 0 
main: 0 0 0 0 0 5 0 0 0 0 
main: 0 0 0 0 0 6 0 0 0 0 
main: 0 0 0 0 0 6 0 0 0 0 
main: 0 0 0 0 0 6 0 0 0 0 
main: 0 0 0 0 0 7 0 0 0 0 
main: 0 0 0 0 0 7 0 0 0 0 
main: 0 0 0 0 0 7 0 0 0 0 
main: 0 0 0 0 0 8 0 0 0 0 
main: 0 0 0 0 0 8 0 0 0 0 
main: 0 0 0 0 0 8 0 0 0 0 
main: 0 0 0 0 0 9 0 0 0 0 
main: 0 0 0 0 0 9 0 0 0 0 
main: 0 0 0 0 0 9 0 0 0 0