`SpinWait`

An idle loop uses 100% CPU. It runs for a specified number of iterations in a C# program. With Thread.SpinWait we specify this iteration count.

Some notes

The CPU will max out for the required amount of time for this to complete. Meanwhile with Thread.Sleep, no CPU usage will occur.

Example

This program uses Thread.SpinWait for one million iterations. It also uses Stopwatch to time how long Thread.SpinWait takes to complete.

Result An argument of 1000000 required about 3 milliseconds to complete on the computer used for testing.

Note Because SpinWait is computationally intensive, it will complete earlier or later depending on your computer's clock speed.

using System;
using System.Diagnostics;
using System.Threading;

Stopwatch stopwatch = Stopwatch.StartNew();
// CPU is at maximum during this call.
// ... (Try making it much larger to test.)
Thread.SpinWait(1000000);
Console.WriteLine(stopwatch.Elapsed.TotalMilliseconds);
3.0908

Discussion

I tried to determine how to adjust the number of threads optimally for a multiple-core machine. SpinWait was helpful in this task.

Info When I used Thread.Sleep, the experiment did not involve the CPU and so did not yield correct results.

But When I used Thread.SpinLock, the results were correct. SpinLock is necessary to simulate actual CPU usage.

Summary

We looked at Thread.SpinWait found in the System.Threading namespace. If you want to waste electricity and make your computer do a lot of computations, this method is perfect.