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/*
* Scala (https://www.scala-lang.org)
*
* Copyright EPFL and Lightbend, Inc.
*
* Licensed under Apache License 2.0
* (http://www.apache.org/licenses/LICENSE-2.0).
*
* See the NOTICE file distributed with this work for
* additional information regarding copyright ownership.
*/
package scala
package collection
import scala.collection.generic.CanBuildFrom
import scala.collection.generic.CanCombineFrom
import scala.collection.parallel.mutable.ParArray
import scala.collection.mutable.UnrolledBuffer
import scala.annotation.unchecked.uncheckedVariance
import scala.language.implicitConversions
/** Package object for parallel collections.
*/
package object parallel {
/* constants */
val MIN_FOR_COPY = 512
val CHECK_RATE = 512
val SQRT2 = math.sqrt(2)
val availableProcessors = java.lang.Runtime.getRuntime.availableProcessors
/* functions */
/** Computes threshold from the size of the collection and the parallelism level.
*/
def thresholdFromSize(sz: Int, parallelismLevel: Int) = {
val p = parallelismLevel
if (p > 1) 1 + sz / (8 * p)
else sz
}
val defaultTaskSupport: TaskSupport = new ExecutionContextTaskSupport
def setTaskSupport[Coll](c: Coll, t: TaskSupport): Coll = {
c match {
case pc: ParIterableLike[_, _, _] => pc.tasksupport = t
case _ => // do nothing
}
c
}
/** Adds toParArray method to collection classes. */
implicit class CollectionsHaveToParArray[C, T](c: C)(implicit asGto: C => scala.collection.GenTraversableOnce[T]) {
def toParArray = {
val t = asGto(c)
if (t.isInstanceOf[ParArray[_]]) t.asInstanceOf[ParArray[T]]
else {
val it = t.toIterator
val cb = mutable.ParArrayCombiner[T]()
while (it.hasNext) cb += it.next
cb.result
}
}
}
}
package parallel {
/** Implicit conversions used in the implementation of parallel collections. */
private[collection] object ParallelCollectionImplicits {
implicit def factory2ops[From, Elem, To](bf: CanBuildFrom[From, Elem, To]) = new FactoryOps[From, Elem, To] {
def isParallel = bf.isInstanceOf[Parallel]
def asParallel = bf.asInstanceOf[CanCombineFrom[From, Elem, To]]
def ifParallel[R](isbody: CanCombineFrom[From, Elem, To] => R) = new Otherwise[R] {
def otherwise(notbody: => R) = if (isParallel) isbody(asParallel) else notbody
}
}
implicit def traversable2ops[T](t: scala.collection.GenTraversableOnce[T]) = new TraversableOps[T] {
def isParallel = t.isInstanceOf[Parallel]
def isParIterable = t.isInstanceOf[ParIterable[_]]
def asParIterable = t.asInstanceOf[ParIterable[T]]
def isParSeq = t.isInstanceOf[ParSeq[_]]
def asParSeq = t.asInstanceOf[ParSeq[T]]
def ifParSeq[R](isbody: ParSeq[T] => R) = new Otherwise[R] {
def otherwise(notbody: => R) = if (isParallel) isbody(asParSeq) else notbody
}
}
implicit def throwable2ops(self: Throwable) = new ThrowableOps {
def alongWith(that: Throwable) = (self, that) match {
case (self: CompositeThrowable, that: CompositeThrowable) => new CompositeThrowable(self.throwables ++ that.throwables)
case (self: CompositeThrowable, _) => new CompositeThrowable(self.throwables + that)
case (_, that: CompositeThrowable) => new CompositeThrowable(that.throwables + self)
case _ => new CompositeThrowable(Set(self, that))
}
}
}
trait FactoryOps[From, Elem, To] {
trait Otherwise[R] {
def otherwise(notbody: => R): R
}
def isParallel: Boolean
def asParallel: CanCombineFrom[From, Elem, To]
def ifParallel[R](isbody: CanCombineFrom[From, Elem, To] => R): Otherwise[R]
}
trait TraversableOps[T] {
trait Otherwise[R] {
def otherwise(notbody: => R): R
}
def isParallel: Boolean
def isParIterable: Boolean
def asParIterable: ParIterable[T]
def isParSeq: Boolean
def asParSeq: ParSeq[T]
def ifParSeq[R](isbody: ParSeq[T] => R): Otherwise[R]
}
@deprecated("this trait will be removed", "2.11.0")
trait ThrowableOps {
@deprecated("this method will be removed", "2.11.0")
def alongWith(that: Throwable): Throwable
}
/* classes */
trait CombinerFactory[U, Repr] {
/** Provides a combiner used to construct a collection. */
def apply(): Combiner[U, Repr]
/** The call to the `apply` method can create a new combiner each time.
* If it does, this method returns `false`.
* The same combiner factory may be used each time (typically, this is
* the case for concurrent collections, which are thread safe).
* If so, the method returns `true`.
*/
def doesShareCombiners: Boolean
}
/** Composite throwable - thrown when multiple exceptions are thrown at the same time. */
@deprecated("this class will be removed.", "2.11.0")
final case class CompositeThrowable(throwables: Set[Throwable]) extends Exception(
"Multiple exceptions thrown during a parallel computation: " +
throwables.map(t => t + "\n" + t.getStackTrace.take(10).++("...").mkString("\n")).mkString("\n\n")
)
/** A helper iterator for iterating very small array buffers.
* Automatically forwards the signal delegate when splitting.
*/
private[parallel] class BufferSplitter[T]
(private val buffer: scala.collection.mutable.ArrayBuffer[T], private var index: Int, private val until: Int, _sigdel: scala.collection.generic.Signalling)
extends IterableSplitter[T] {
signalDelegate = _sigdel
def hasNext = index < until
def next = {
val r = buffer(index)
index += 1
r
}
def remaining = until - index
def dup = new BufferSplitter(buffer, index, until, signalDelegate)
def split: Seq[IterableSplitter[T]] = if (remaining > 1) {
val divsz = (until - index) / 2
Seq(
new BufferSplitter(buffer, index, index + divsz, signalDelegate),
new BufferSplitter(buffer, index + divsz, until, signalDelegate)
)
} else Seq(this)
private[parallel] override def debugInformation = {
buildString {
append =>
append("---------------")
append("Buffer iterator")
append("buffer: " + buffer)
append("index: " + index)
append("until: " + until)
append("---------------")
}
}
}
/** A helper combiner which contains an array of buckets. Buckets themselves
* are unrolled linked lists. Some parallel collections are constructed by
* sorting their result set according to some criteria.
*
* A reference `buckets` to buckets is maintained. Total size of all buckets
* is kept in `sz` and maintained whenever 2 bucket combiners are combined.
*
* Clients decide how to maintain these by implementing `+=` and `result`.
* Populating and using the buckets is up to the client. While populating them,
* the client should update `sz` accordingly. Note that a bucket is by default
* set to `null` to save space - the client should initialize it.
* Note that in general the type of the elements contained in the buckets `Buck`
* doesn't have to correspond to combiner element type `Elem`.
*
* This class simply gives an efficient `combine` for free - it chains
* the buckets together. Since the `combine` contract states that the receiver (`this`)
* becomes invalidated, `combine` reuses the receiver and returns it.
*
* Methods `beforeCombine` and `afterCombine` are called before and after
* combining the buckets, respectively, given that the argument to `combine`
* is not `this` (as required by the `combine` contract).
* They can be overridden in subclasses to provide custom behaviour by modifying
* the receiver (which will be the return value).
*/
private[parallel] abstract class BucketCombiner[-Elem, +To, Buck, +CombinerType <: BucketCombiner[Elem, To, Buck, CombinerType]]
(private val bucketnumber: Int)
extends Combiner[Elem, To] {
//self: EnvironmentPassingCombiner[Elem, To] =>
protected var buckets: Array[UnrolledBuffer[Buck]] @uncheckedVariance = new Array[UnrolledBuffer[Buck]](bucketnumber)
protected var sz: Int = 0
def size = sz
def clear() = {
buckets = new Array[UnrolledBuffer[Buck]](bucketnumber)
sz = 0
}
def beforeCombine[N <: Elem, NewTo >: To](other: Combiner[N, NewTo]) {}
def afterCombine[N <: Elem, NewTo >: To](other: Combiner[N, NewTo]) {}
def combine[N <: Elem, NewTo >: To](other: Combiner[N, NewTo]): Combiner[N, NewTo] = {
if (this eq other) this
else other match {
case _: BucketCombiner[_, _, _, _] =>
beforeCombine(other)
val that = other.asInstanceOf[BucketCombiner[Elem, To, Buck, CombinerType]]
var i = 0
while (i < bucketnumber) {
if (buckets(i) eq null)
buckets(i) = that.buckets(i)
else if (that.buckets(i) ne null)
buckets(i) concat that.buckets(i)
i += 1
}
sz = sz + that.size
afterCombine(other)
this
case _ =>
sys.error("Unexpected combiner type.")
}
}
}
}
