scala.collection.parallel.TaskSupport

trait TaskSupport extends Tasks

A trait implementing the scheduling of a parallel collection operation.

Parallel collections are modular in the way operations are scheduled. Each parallel collection is parametrized with a task support object which is responsible for scheduling and load-balancing tasks to processors.

A task support object can be changed in a parallel collection after it has been created, but only during a quiescent period, i.e. while there are no concurrent invocations to parallel collection methods.

There are currently a few task support implementations available for parallel collections. The scala.collection.parallel.ForkJoinTaskSupport uses a fork-join pool internally.

The scala.collection.parallel.ExecutionContextTaskSupport uses the default execution context implementation found in scala.concurrent, and it reuses the thread pool used in scala.concurrent.

The execution context task support is set to each parallel collection by default, so parallel collections reuse the same fork-join pool as the future API.

Here is a way to change the task support of a parallel collection:

import scala.collection.parallel._
val pc = mutable.ParArray(1, 2, 3)
pc.tasksupport = new ForkJoinTaskSupport(
  new java.util.concurrent.ForkJoinPool(2))

Type Members

trait WrappedTask[R, +Tp] extends AnyRef

  • Definition Classes
    • Tasks

Abstract Value Members From scala.collection.parallel.Tasks

abstract def executeAndWaitResult[R, Tp](task: Task[R, Tp]): R

Executes a result task, waits for it to finish, then returns its result. Forwards an exception if some task threw it.

  • Definition Classes
    • Tasks

(defined at scala.collection.parallel.Tasks)

abstract def execute[R, Tp](fjtask: Task[R, Tp]): () ⇒ R

Executes a task and returns a future. Forwards an exception if some task threw it.

  • Definition Classes
    • Tasks

(defined at scala.collection.parallel.Tasks)

Concrete Value Members From scala.collection.parallel.Tasks

abstract val environment: AnyRef

The type of the environment is more specific in the implementations.

  • Definition Classes
    • Tasks

(defined at scala.collection.parallel.Tasks)

Concrete Value Members From Implicit scala.collection.parallel.CollectionsHaveToParArray ——————————————————————————–

def toParArray: ParArray[T]

  • Implicit information
    • This member is added by an implicit conversion from TaskSupport to CollectionsHaveToParArray [TaskSupport, T] performed by method CollectionsHaveToParArray in scala.collection.parallel. This conversion will take place only if an implicit value of type (TaskSupport) ⇒ GenTraversableOnce [T] is in scope.
  • Definition Classes
    • CollectionsHaveToParArray (added by implicit convertion: scala.collection.parallel.CollectionsHaveToParArray)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package collection.parallel

import java.util.concurrent.ThreadPoolExecutor
import java.util.concurrent.ForkJoinPool
import scala.concurrent.ExecutionContext

/** A trait implementing the scheduling of a parallel collection operation.
 *
 *  Parallel collections are modular in the way operations are scheduled. Each
 *  parallel collection is parametrized with a task support object which is
 *  responsible for scheduling and load-balancing tasks to processors.
 *
 *  A task support object can be changed in a parallel collection after it has
 *  been created, but only during a quiescent period, i.e. while there are no
 *  concurrent invocations to parallel collection methods.
 *
 *  There are currently a few task support implementations available for
 *  parallel collections. The [[scala.collection.parallel.ForkJoinTaskSupport]]
 *  uses a fork-join pool internally.
 *
 *  The [[scala.collection.parallel.ExecutionContextTaskSupport]] uses the
 *  default execution context implementation found in scala.concurrent, and it
 *  reuses the thread pool used in scala.concurrent.
 *
 *  The execution context task support is set to each parallel collection by
 *  default, so parallel collections reuse the same fork-join pool as the
 *  future API.
 *
 *  Here is a way to change the task support of a parallel collection:
 *
 *  {{{
 *  import scala.collection.parallel._
 *  val pc = mutable.ParArray(1, 2, 3)
 *  pc.tasksupport = new ForkJoinTaskSupport(
 *    new java.util.concurrent.ForkJoinPool(2))
 *  }}}
 *
 *  @see [[http://docs.scala-lang.org/overviews/parallel-collections/configuration.html Configuring Parallel Collections]] section
 *    on the parallel collection's guide for more information.
 */
trait TaskSupport extends Tasks

/** A task support that uses a fork join pool to schedule tasks.
 *
 *  @see [[scala.collection.parallel.TaskSupport]] for more information.
 */
class ForkJoinTaskSupport(val environment: ForkJoinPool = ForkJoinTasks.defaultForkJoinPool)
extends TaskSupport with AdaptiveWorkStealingForkJoinTasks

/** A task support that uses a thread pool executor to schedule tasks.
 *
 *  @see [[scala.collection.parallel.TaskSupport]] for more information.
 */
@deprecated("Use `ForkJoinTaskSupport` instead.", "2.11.0")
class ThreadPoolTaskSupport(val environment: ThreadPoolExecutor = ThreadPoolTasks.defaultThreadPool)
extends TaskSupport with AdaptiveWorkStealingThreadPoolTasks

/** A task support that uses an execution context to schedule tasks.
 *
 *  It can be used with the default execution context implementation in the
 *  `scala.concurrent` package. It internally forwards the call to either a
 *  forkjoin based task support or a thread pool executor one, depending on
 *  what the execution context uses.
 *
 *  By default, parallel collections are parametrized with this task support
 *  object, so parallel collections share the same execution context backend
 *  as the rest of the `scala.concurrent` package.
 *
 *  @see [[scala.collection.parallel.TaskSupport]] for more information.
 */
class ExecutionContextTaskSupport(val environment: ExecutionContext = scala.concurrent.ExecutionContext.global)
extends TaskSupport with ExecutionContextTasks