Differences between @async and @schedule?

[Spencer Russell]

From the docs I gather that `@schedule operation()` is equivalent to `schedule(@task operation())`, In that `operation()` will be wrapped in a task and added as a runnable item in the scheduler queue.

`@async` says it wraps the expression in a closure rather than a task, but likewise adds it to the scheduler queue. It also adds it to the list of things that the enclosing `@sync` is waiting for, so that’s definitely another difference from `@schedule`

What are the practical differences between wrapping an expression in a Task rather than a closure before adding it to the scheduler queue?

-s

[Steven G. Johnson]

On Thursday, September 3, 2015 at 1:48:33 AM UTC-4, Spencer Russell wrote:

From the docs I gather that `@schedule operation()` is equivalent to `schedule(@task operation())`, In that `operation()` will be wrapped in a task and added as a runnable item in the scheduler queue.

`@async` says it wraps the expression in a closure rather than a task, but likewise adds it to the scheduler queue. It also adds it to the list of things that the enclosing `@sync` is waiting for, so that’s definitely another difference from `@schedule`

Hopefully you are trying to write better documentation for these things, like you mentioned in a previous thread; documentation improvements are always welcome.   The best way to answer questions about under-documented functions is to look at the source, in this case https://github.com/JuliaLang/julia/blob/master/base/task.jl

Both @async and @schedule create a closure and wrap it in a Task which is enqueued.  Look at "macro async" vs. "macro schedule" ... they both do something like enq_work(Task(() -> expr)).

The difference is that @async does two additional things.  First, as you mentioned, it adds it to the @sync stack.  Second, it calls "localize_vars" (defined in expr.jl), which wraps an expression in "let a=a, b=b, ..." for each variable it references; however, this second behavior is fairly likely to be changed, see: https://github.com/JuliaLang/julia/issues/7813 and https://github.com/JuliaLang/julia/issues/8591