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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala.collection.parallel
import java.util.concurrent.ThreadPoolExecutor
import scala.concurrent.forkjoin.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 and is used by default on JVM 1.6 or greater. The less efficient
* [[scala.collection.parallel.ThreadPoolTaskSupport]] is a fallback for JVM
* 1.5 and JVMs that do not support the fork join pools. 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 (this is either a fork join
* pool or a thread pool executor, depending on the JVM version). 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 scala.concurrent.forkjoin.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.
*/
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
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