How to Create a New Thread in C++

In C++, creating new threads is a powerful way to take advantage of multiple processors or cores and maximize program performance. Threads enable multiple independent processes to execute simultaneously, allowing programs to perform multiple tasks at once. This can be particularly useful for CPU-intensive applications, such as those involving scientific or mathematical computations or those that require significant input/output operations.

Creating a new thread in C++ involves several steps, including defining the thread function, creating a thread object, and executing the thread. In this article, we'll explore each of these steps in more detail.

Defining the Thread Function

The first step in creating a new thread is to define the function that will be executed in the new thread. This function should perform the tasks that the thread is intended to carry out. For example, if the thread is intended to perform some computation or data processing, the function should contain the relevant code.

The function should have a specific signature that matches the requirements of the thread library. In C++, this usually means that the function should take a void pointer as its argument and return a void pointer. This allows the function to receive data and return results through pointers.

Here's an example of a thread function that computes the sum of an array of integers:

Program 1

Output:

Explanation:

In this example, the function takes a void pointer as its argument and casts it to an integer array. It then computes the sum of the array elements and returns the result as a void pointer.

Creating a Thread Object

Once the thread function has been defined, the next step is to create a thread object. In C++, this is typically done using the std::thread class, which is part of the C++ Standard Library.

To create a new thread object, you need to pass the thread function and any required arguments as arguments to the std::thread constructor. Here's an example of how to create a new thread object for the sum_array function defined earlier:

Program 2

Output:

Explanation:

In this example, we create a new integer array and pass it to the sum_array function as an argument. We then create a new std::thread object, passing the sum_array function and the array argument as arguments to the constructor.

Executing the Thread

Once the thread object has been created, the next step is to execute the thread. This is done by calling the std::thread::join method, which starts the thread and waits for it to complete.

Program 3

Output:

Explanation:

In this example, we create a new thread object and call the join method on the object. This starts the thread and waits for it to complete before continuing with the rest of the program.

It's important to note that the join method can only be called once on a thread object. If you need to execute the same thread function multiple times, you'll need to create a new thread object for each execution.

Conclusion

While creating new threads in C++ can be a powerful technique for optimizing program performance, it's important to use it judiciously. Threads require additional memory and processing resources, and excessive thread usage can lead to performance degradation and other issues. Additionally, threads can introduce synchronization and concurrency issues, which must be carefully managed to avoid race conditions and other problems.

Overall, creating new threads in C++ requires careful planning and execution. However, by following best practices for thread design and management, programmers can unlock multi-core processors' full potential and achieve optimal program performance.