OpenMP - 编译制导（二）

section制导

OpenMP中的section子句是用于在sections子句内部将代码划分成几个不同的段。当与#pragma omp parallel sections结合使用时，这些代码段会并行处理。每个section由其中的一个线程执行一次，不同的section可以由不同的线程执行。当然，如果一个线程运行得足够快，它可能会执行多个section。

#include <iostream>
#include <omp.h>
using namespace std;

int main(int argc, char* argv[]){
    int a[5];
    #pragma omp parallel sections
    {
        #pragma omp section
        {
            a[0] = omp_get_thread_num();
        }
        #pragma omp section
        {
            a[1] = omp_get_thread_num();
        }
        #pragma omp section
        {
            a[2] = omp_get_thread_num();
        }
        #pragma omp section
        {
            a[3] = omp_get_thread_num();
        }
        #pragma omp section
        {
            a[4] = omp_get_thread_num();
        }
    }

    for (int i = 0; i < 5; ++i) {
        cout << "section " << i << " -> " << "thread " << a[i] << endl;
    }
    return 0;
}

 section 0 -> thread 0
section 1 -> thread 0
section 2 -> thread 1
section 3 -> thread 2
section 4 -> thread 3

 section 0 -> thread 0
section 1 -> thread 0
section 2 -> thread 1
section 3 -> thread 1
section 4 -> thread 2
section 5 -> thread 3

 section 0 -> thread 0
section 1 -> thread 1

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