Using Multiple Threads with Parallel LINQ

By default, only one thread is used to execute a LINQ query. Parallel LINQ (PLINQ) is an easy way to enable multiple threads to execute a LINQ query.

Note: Do not assume that using parallel threads will improve the performance of applications. Always measure real-world timings and resource usage.

Creating an app that benefits from multiple threads

To see it in action, we will start with some code that only uses a single thread to calculate Fibonacci numbers for 45 integers. We will use the StopWatch type to measure the change in performance. We will use operating system tools to monitor the CPU and CPU core usage. This exercise won’t show much if we do not have multiple CPUs or at least multiple cores.

Step 1: Use your preferred code editor to add a new Console App or  console project named LinqInParallel to the Chapter11 solution or workspace.

• In Visual Studio Code, select LinqInParallel as the active OmniSharp project.

Step 2: In Program.cs, delete the existing statements and then import the System.Diagnostics namespace so that we can use the StopWatch type. Add statements to create a stopwatch to record timings, wait for a keypress before starting the timer, create 45 integers, calculate the Fibonacci number for each of them, stop the timer, and display the elapsed milliseconds, as shown in the following code: