Is it true that async should not be used for high-CPU tasks?

Question

I was wondering whether it's true that async-await should not be used for "high-CPU" tasks. I saw this claimed in a presentation.

So I guess that would mean something like

Task<int> calculateMillionthPrimeNumber = CalculateMillionthPrimeNumberAsync(); DoIndependentWork(); int p = await calculateMillionthPrimeNumber; 

My question is could the above be justified, or if not, is there some other example of making a high-CPU task async?

Answer 1

I was wondering whether it's true that async-await should not be used for "high-CPU" tasks.

Yes, that's true.

My question is could the above be justified

I would say that it is not justified. In the general case, you should avoid using Task.Run to implement methods with asynchronous signatures. Don't expose asynchronous wrappers for synchronous methods. This is to prevent confusion by consumers, particularly on ASP.NET.

However, there is nothing wrong with using Task.Run to call a synchronous method, e.g., in a UI app. In this way, you can use multithreading (Task.Run) to keep the UI thread free, and consume it elegantly with await:

var task = Task.Run(() => CalculateMillionthPrimeNumber()); DoIndependentWork(); var prime = await task;