Fixing Compilation Errors in C+ + Multithreading with std::thread

Learn how to properly use `std::thread` in C+ + for multithreading applications, and resolve common compilation errors effectively.
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Fixing Compilation Errors in C+ + Multithreading with std::thread

C+ + has powerful multithreading capabilities through the std::thread library, but using it correctly can sometimes be challenging. In this post, we'll address a common issue that arises when attempting to implement multithreading in C+ + . This issue involves compilation errors stemming from incorrect syntax when creating threads using std::thread. We'll explore the correct way to define threads and provide a detailed code example based on a parallel accumulator class implementation.

The Problem

When working with threads in C+ + , you might frequently encounter compilation issues, particularly when passing parameters to thread functions. In the example you're developing, you have a ParallelAccumulator class designed to accumulate contributions in parallel. However, the compilation fails when you attempt to create threads that call the test_function. Below is a summary of the code that produced an error:

[[See Video to Reveal this Text or Code Snippet]]

This line, along with similar lines for creating more threads, raises errors related to incompatible data types, specifically concerning the output array.

The Compilation Errors

The errors are primarily caused by passing a variable-sized array (double array[num_elements]) directly to std::thread. The compiler does not accept this format and reports errors indicating that no suitable function overload was found for the thread constructor.

The Solution

Thanks to community inputs, including insights from users like @ doron, we can resolve this issue by modifying the way we reference the output array. Here’s how:

Step 1: Declare num_elements as constexpr

To start, ensure that num_elements is defined as a constexpr constant at the beginning of the main function to maintain compatibility and ease of use.

Step 2: Pass the Correct Reference to the output Array

Instead of passing the output array directly, you need to pass the address of the first element of the array using the & operator in conjunction with an array dereference. This can be done as follows:

[[See Video to Reveal this Text or Code Snippet]]

Full Implementation Example

Combining all the changes, your main function should look like this:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these steps, you've learned the proper syntax for using std::thread in C+ + while resolving common compilation issues related to parameter passing. Remember to always manage thread safety and ensure thread resources are appropriately handled to avoid deadlocks and other concurrency issues. Happy coding!