如何使用OpenMP的#pragma指令创建独立线程分段处理数值迭代任务

可均等划分总迭代数50的线程数 #

50的所有正约数均可：1、2、5、10、25、50 #

公共依赖&编译命令 #

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

// 示例Foo函数，可自定义逻辑、返回值类型
inline int Foo(int p = 0) {
    // 此处替换为实际业务逻辑
    return p * 2;
}

编译命令：g++ 代码文件名.cpp -o 可执行文件名 -fopenmp #

场景1：5线程分段迭代p（总迭代50次） #

int main() {
    const int total_iteration_size = 50;
    const int thread_num = 5;
    omp_set_num_threads(thread_num);

    #pragma omp parallel
    {
        int tid = omp_get_thread_num();
        int per_thread_cnt = total_iteration_size / thread_num;
        int range_start = tid * per_thread_cnt;
        int range_end = (tid + 1) * per_thread_cnt - 1;
        int p = range_start;

        while (p <= range_end) {
            // 替换为实际迭代逻辑
            std::cout << "线程" << tid << " 迭代值p=" << p << std::endl;
            p++;
        }
    }
    return 0;
}

场景2：3线程均等调用Foo函数（总调用30次） #

int main() {
    const int total_call_cnt = 30;
    const int thread_num = 3;
    omp_set_num_threads(thread_num);

    #pragma omp parallel
    {
        int tid = omp_get_thread_num();
        int per_thread_call = total_call_cnt / thread_num;
        int cnt = 0;

        while (cnt < per_thread_call) {
            int res = Foo();
            std::cout << "线程" << tid << " 第" << cnt + 1 << "次调用Foo 返回值=" << res << std::endl;
            cnt++;
        }
    }
    return Foo();
}

场景3：2线程先迭代p、再传参调用Foo（总迭代20次，总调用20次） #

int main() {
    const int total_cnt = 20;
    const int thread_num = 2;
    omp_set_num_threads(thread_num);
    int final_res;

    #pragma omp parallel
    {
        int tid = omp_get_thread_num();
        int per_thread_cnt = total_cnt / thread_num;
        int range_start = tid * per_thread_cnt;
        int range_end = (tid + 1) * per_thread_cnt - 1;

        // 第一步：分段迭代p
        int p = range_start;
        while (p <= range_end) {
            std::cout << "线程" << tid << " 迭代值p=" << p << std::endl;
            p++;
        }

        // 第二步：分段传参调用Foo
        p = range_start;
        int cnt = 0;
        while (cnt < per_thread_cnt) {
            int res = Foo(p);
            std::cout << "线程" << tid << " 调用Foo(" << p << ") 返回值=" << res << std::endl;
            p++;
            cnt++;
        }
    }

    final_res = Foo(20);
    std::cout << "最终调用Foo返回值：" << final_res << std::endl;
    return final_res;
}

内容的提问来源于stack exchange，提问作者AncientTides