Block until all rayon::spawn have completed

[gyscos]

Until we have a way to parallelize a generic non-Send iterator, I'm using rayon::spawn from a single-threaded loop.
This works, except that the main thread will not wait for the tasks to complete before exiting.
Is there a way to block until all global tasks have been completed? Or should I maintain my own completion count for that?

[cuviper]

We don't currently have a way to wait for idle, but I think we probably should.

[wagnerf42]

how about using a scope ?

[cuviper]

Indeed, a scope will not return until all of its Scope::spawns have completed. However, it does require that the initial closure is Send (#562), so @gyscos would have to create their non-Send iterator from within. And since this consumes one thread of the pool, you probably want to make sure there are more threads to do the spawned work, otherwise the whole iterator will be processed before getting to the spawns.

[gsquire]

Perhaps you could leverage a WaitGroup?

[cuviper]

Note: we do have in_place_scope now, without Send, so you can spawn tasks from the current thread and have a well-defined wait at the end of that scope.