Is Parallel.Invoke same as calling multiple Task.Run's?

Question

Task.Run: Queues the specified work to run on the ThreadPool and returns a task or Task<TResult> handle for that work.

Parallel.Invoke: Executes each of the provided actions, possibly in parallel.

Effectively they spin up a new thread from the thread pool. So is Parallel.Invoke same as calling multiple Task.Runs?

Answer 1

So you want to compare these two techniques:

Parallel.Invoke(source.Select(source => () => ProcessItem(source)).ToArray());

Task.WaitAll(source.Select(source => Task.Run(() => ProcessItem(source))).ToArray());

There is one similarity and two differences. The similarity is that in both cases all actions will be invoked and completed before the Parallel.Invoke/Task.WaitAll returns. It doesn't matter if some of the actions fail. There is no support for a fail-fast strategy.

The two differences are:

1. The Parallel.Invoke uses the current thread as one of the worker threads. On the contrary the Task.WaitAll+Task.Run uses exclusively ThreadPool threads. While the worker threads are working, the current thread is blocked doing nothing.

2. The Parallel.Invoke can be configured with a specific MaxDegreeOfParallelism, TaskScheduler and CancellationToken (ParallelOptions). This is not possible with the Task.Run. It is possible with the Task.Factory.StartNew, but comparatively it's quite cumbersome.