Concurrent map/foreach in scala

Question

I have an iteration vals: Iterable[T] and a long-running function without any relevant side effects: f: (T => Unit). Right now this is applied to vals in the obvious way:

vals.foreach(f)

I would like the calls to f to be done concurrently (within reasonable limits). Is there an obvious function somewhere in the Scala base library? Something like:

Concurrent.foreach(8 /* Number of threads. */)(vals, f)

While f is reasonably long running, it is short enough that I don't want the overhead of invoking a thread for each call, so I am looking for something based on a thread pool.

Answer 1

Many of the answers from 2009 still use the old scala.actors.Futures._, which are no longer in the newer Scala. While Akka is the preferred way, a much more readable way is to just use parallel (.par) collections:

vals.foreach { v => f(v) }

becomes

vals.par.foreach { v => f(v) }

Alternatively, using parMap can appear more succinct though with the caveat that you need to remember to import the usual Scalaz*. As usual, there's more than one way to do the same thing in Scala!