Multithreading in C++ -Thread creations and basic functions in thread

Multithreading in C++

              Thread is a light weight process under execution. If multiple threads are running, it need to manage memory, simultaneous threads. In c++, there is a header file <thread> which supports multithreading.

How to create a thread?

A thread is created by the use of std::thread class. The syntax is given below.

Syntax:

thread thread_name(callable);

here, thread_name is the object for the thread class.

‘callable’- it is a object for function object.

Eg:

• ·       This c++ program includes the header file bits/stdc++.h.
• ·       It creates a function func() with a thread message to display.
• ·       Next, a main() function is created with threat t calling a function func() and an object is created for thread as t.
• ·       The object t calls a function join() and display a message.

Code:

#include <bits/stdc++.h>

using namespace std;

void func() {

    cout << "It is a message from the thread!" << endl;

}

int main() {

    thread t(func);

    t.join(); 

    cout << "It is the Main thread.";

    return 0;

}

Output:

It is a message from the thread!

It is the Main thread.

Thread functions:

The operations can be performed on threads are given below.

• Getting Thread ID – It thread_name.get_id();
• ‘join()’ – thread_name.join();
• Detaching thread -thread_name.detach();

Let us create c++ Program for illustrate the thread functions.

#include <iostream>

#include <thread>

#include <chrono>

using namespace std;

void getid1() {

    cout << "Thread1's ID: " << this_thread::get_id() << "\n";

}

void getid2() {

    cout << "Thread2's ID: " << this_thread::get_id() << "\n";

}

int main() {

    thread t1(getid1);

    thread t2(getid2);

    // let us Get thread IDs

    cout << "t1 ID: " << t1.get_id() << "\n";

    cout << "t2 ID: " << t2.get_id() << "\n";

    // let us Join the thread1 if joinable

    if (t1.joinable()) {

        t1.join();

        cout << "thread1 is joined\n";

    }

    // let us detach the thread2

    if (t2.joinable()) {

        t2.detach();

        cout << "thread2 is detached\n";

    }

    cout << "Main thread is sleeping for 5 seconds...\n";

    this_thread::sleep_for(chrono::seconds(5));

    cout << "Now,Main thread is awake after 5 seconds.\n";

    return 0;

}

Output:

t1 ID: 134838204831424

t2 ID: 134838196438720

Thread2's ID: 134838196438720

Thread1's ID: 134838204831424

thread1 is joined

thread2 is detached

Main thread is sleeping for 5 seconds...

Now,Main thread is awake after 5 seconds.

Hope you understood the basics of multithreading and its operations in c++. The programs included in this blog helps you to know about thread creation and its functions usage. Keep Coding.