C++ Multithreading

01_README.md

C++ Multithreading example

https://www.tutorialspoint.com/cplusplus/cpp_quick_guide.htm

main.cpp

#if TREAD_1
// basic
#include <iostream>
#include <cstdlib>
#include <pthread.h>

using namespace std;

#define NUM_THREADS 5

void* PrintHello(void* threadid) {
    long tid;
    tid = (long)threadid;
    cout << "Hello World! Thread ID, " << tid << endl;
    pthread_exit(NULL);
}

int main() {
    pthread_t threads[NUM_THREADS];
    int rc;
    int i;

    for (i = 0; i < NUM_THREADS; i++) {
        cout << "main() : creating thread, " << i << endl;
        rc = pthread_create(&threads[i], NULL, PrintHello, (void*)i);

        if (rc) {
            cout << "Error:unable to create thread," << rc << endl;
            exit(-1);
        }
    }
    pthread_exit(NULL);
}
#elif TREAD_2
// passing arguments
#include <iostream>
#include <cstdlib>
#include <pthread.h>

using namespace std;

#define NUM_THREADS 5

struct thread_data {
    int  thread_id;
    char* message;
};

void* PrintHello(void* threadarg) {
    struct thread_data* my_data;
    my_data = (struct thread_data*)threadarg;

    cout << "Thread ID : " << my_data->thread_id;
    cout << " Message : " << my_data->message << endl;

    pthread_exit(NULL);
}

int main() {
    pthread_t threads[NUM_THREADS];
    struct thread_data td[NUM_THREADS];
    int rc;
    int i;

    for (i = 0; i < NUM_THREADS; i++) {
        cout << "main() : creating thread, " << i << endl;
        td[i].thread_id = i;
        td[i].message = "This is message";
        rc = pthread_create(&threads[i], NULL, PrintHello, (void*)&td[i]);

        if (rc) {
            cout << "Error:unable to create thread," << rc << endl;
            exit(-1);
        }
    }
    pthread_exit(NULL);
}
#elfi THREAD_3
//Join and detach
#include <iostream>
#include <cstdlib>
#include <pthread.h>
#include <unistd.h>

using namespace std;

#define NUM_THREADS 5

void* wait(void* t) {
    int i;
    long tid;

    tid = (long)t;

    sleep(1);
    cout << "Sleeping in thread " << endl;
    cout << "Thread with id : " << tid << "  ...exiting " << endl;
    pthread_exit(NULL);
}

int main() {
    int rc;
    int i;
    pthread_t threads[NUM_THREADS];
    pthread_attr_t attr;
    void* status;

    // Initialize and set thread joinable
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

    for (i = 0; i < NUM_THREADS; i++) {
        cout << "main() : creating thread, " << i << endl;
        rc = pthread_create(&threads[i], &attr, wait, (void*)i);
        if (rc) {
            cout << "Error:unable to create thread," << rc << endl;
            exit(-1);
        }
    }

    // free attribute and wait for the other threads
    pthread_attr_destroy(&attr);
    for (i = 0; i < NUM_THREADS; i++) {
        rc = pthread_join(threads[i], &status);
        if (rc) {
            cout << "Error:unable to join," << rc << endl;
            exit(-1);
        }
        cout << "Main: completed thread id :" << i;
        cout << "  exiting with status :" << status << endl;
    }

    cout << "Main: program exiting." << endl;
    pthread_exit(NULL);
}
#endif