Is it a good idea to run `...par.map(` on large lists directly?
parallel-collections, scala
Solution
Run `par.map` directly, as it already takes the number of cores into account. However, do not keep a `List`, as that requires a full copy to make into a parallel collection. Instead, use `Vector`.
Problem
Let's say I have a somewhat large (several millions of items, or so) list of strings. Is it a good idea to run something like this: ``` val updatedList = myList.par.map(someAction).toList ``` Or would it be a better idea to group the list before running `...par.map(`, like this: ``` val numberOfCores = Runtime.getRuntime.availableProcessors val updatedList = myList.grouped(numberOfCores).toList.par.map(_.map(someAction)).toList.flatten ``` UPDATE: Given that `someAction` is quite expensive (comparing to `grouped`, `toList`, etc.)