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scalaparallel-collections

Is this scala parallel array code threadsafe?

I want to use parallel arrays for a task, and before I start with the coding, I'd be interested in knowing if this small snipept is threadsafe:

import collection.mutable._

var listBuffer = ListBuffer[String]("one","two","three","four","five","six","seven","eight","nine")
var jSyncList  = java.util.Collections.synchronizedList(new java.util.ArrayList[String]())
listBuffer.par.foreach { e =>
    println("processed :"+e)
    // using sleep here to simulate a random delay
    Thread.sleep((scala.math.random * 1000).toLong)
    jSyncList.add(e)
}
jSyncList.toArray.foreach(println)

Are there better ways of processing something with parallel collections, and acumulating the results elsewhere?

Solution

  • The code you posted is perfectly safe; I'm not sure about the premise though: why do you need to accumulate the results of a parallel collection in a non-parallel one? One of the whole points of the parallel collections is that they look like other collections.

    I think that parallel collections also will provide a seq method to switch to sequential ones. So you should probably use this!