13.17. Parallel Collections

It is hard to write correct concurrent programs, yet concurrency is often required nowadays to keep all processors of a computer busy. Scala offers a particularly attractive solution for tasks that manipulate large collections. Such tasks often parallelize naturally. For example, to compute the sum of all elements, multiple threads can concurrently compute the sums of different sections; in the end, these partial results are summed up. Of course it is troublesome to schedule these concurrent activities—but with Scala, you don’t have to. If coll is a large collection, then

coll.par.sum