來自不同進程的線程可以具有相同的ID嗎？

Question

我正在編寫一個程序，其中我想為每個進程創建多個進程和多個線程。 簡而言之，我的程序創建了多個進程，每個進程創建了多個線程。

這是代碼的簡短片段：

void NormalityComponent::newThread(int thread_id){
    std::cout << "New Thread [" << thread_id +1 << "] created in Component [" << name_component << "] with id " << std::this_thread::get_id() << std::endl;
    timeSimulation();
    std::cout << "Thread [" << thread_id +1 << "] in [" << name_component << "] with id " << std::this_thread::get_id() << " ends its simulation" << std::endl;
}

void NormalityComponent::timeSimulation(){
    for (int i = 0; i < time_factor * TEMPORAL_PARAMETER; i++);    
}

void NormalityComponent::startAnalysisMode3(){
    //creation of a new process to simulate the Normality Component Analysis and a thread for each Instance.

            pid_t pid = fork();
            if (pid == 0){
                  //Child Process
                  std::cout << "New Normality Component ["<< name_component <<"] created with id " << getpid() << std::endl;
                  //Creation of instances
                    for(int i = 0; i < number_instances;i++){
                        v_threads.push_back(std::thread(&NormalityComponent::newThread,this, i));
                        std::this_thread::sleep_for (std::chrono::milliseconds(100));
                    }

                    std::for_each(v_threads.begin(), v_threads.end(), std::mem_fn(&std::thread::join));

                    kill(getpid(), SIGTERM); //it ends the process when the threads finish. 
            }
}

這是輸出的一部分：

New Thread [1] created in Component [Velocity] with id 140236340983552
New Thread [1] created in Component [FaceRecognition] with id 140236340983552
New Thread [1] created in Component [Trajectories] with id 140236340983552
New Thread [2] created in Component [Velocity] with id 140236332590848
New Thread [2] created in Component [Trajectories] with id 140236332590848
New Thread [2] created in Component [FaceRecognition] with id 140236332590848

來自不同進程的線程可以具有相同的ID嗎？ 很奇怪，每個線程的標識符應該唯一，對吧？

Answer 1

這些線程ID看起來更像地址。 由this_thread::get_id()返回的值不必與系統“線程ID”相同。 它主要用於提供字符串比較/作為關聯容器中線程的鍵的目的。 您可能想嘗試調用gettid或GetCurrentThreadId 。 請注意，在窗口“直到線程終止之前，線程標識符唯一地標識整個系統中的線程。” 因此來自不同進程的線程不能具有相同的ID。 在其他平台上，行為可能有所不同。

Answer 2

您可能想嘗試調用gettid或GetCurrentThreadId

@ VTT，gettid（）對我有用。

void NormalityComponent::newThread(int thread_id){
pid_t tid = (pid_t) syscall (SYS_gettid);

std::cout << "New Thread [" << thread_id +1 << "] created in Component [" << name_component << "] with id " << tid << std::endl;
timeSimulation();
std::cout << "Thread [" << thread_id +1 << "] in [" << name_component << "] with id " << tid << " ends its simulation" << std::endl;

}

該解決方案為每個線程提供唯一的標識符。 輸出示例如下：

New Normality Component [Trajectories] created with id 5118
New Normality Component [Velocity] created with id 5119
New Thread [1] created in Component [Trajectories] with id 5121
New Normality Component [FaceRecognition] created with id 5120
New Thread [1] created in Component [Velocity] with id 5122
New Thread [1] created in Component [FaceRecognition] with id 5123
New Thread [2] created in Component [Trajectories] with id 5124
New Thread [2] created in Component [Velocity] with id 5125
New Thread [2] created in Component [FaceRecognition] with id 5126
Thread [1] in [Velocity] with id 5122 ends its simulation
New Thread [3] created in Component [Trajectories] with id 5127
New Thread [3] created in Component [FaceRecognition] with id 5128
New Thread [4] created in Component [FaceRecognition] with id 5129

無論如何，我想了解為什么this_thread :: get_id（）不返回線程ID。 如果查看c ++文檔，您將看到函數說明如何指示其返回線程標識符。