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/* __ *\
** ________ ___ / / ___ Scala API **
** / __/ __// _ | / / / _ | (c) 2003-2013, LAMP/EPFL **
** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ **
** /____/\___/_/ |_/____/_/ | | **
** |/ **
\* */
package scala
package collection.parallel.immutable
import scala.collection.parallel.ParSetLike
import scala.collection.parallel.Combiner
import scala.collection.parallel.IterableSplitter
import scala.collection.mutable.UnrolledBuffer.Unrolled
import scala.collection.mutable.UnrolledBuffer
import scala.collection.generic.ParSetFactory
import scala.collection.generic.CanCombineFrom
import scala.collection.generic.GenericParTemplate
import scala.collection.generic.GenericParCompanion
import scala.collection.generic.GenericCompanion
import scala.collection.immutable.{ HashSet, TrieIterator }
import scala.collection.parallel.Task
/** Immutable parallel hash set, based on hash tries.
*
* $paralleliterableinfo
*
* $sideeffects
*
* @tparam T the element type of the set
*
* @author Aleksandar Prokopec
* @since 2.9
* @see [[http://docs.scala-lang.org/overviews/parallel-collections/concrete-parallel-collections.html#parallel_hash_tries Scala's Parallel Collections Library overview]]
* section on Parallel Hash Tries for more information.
*
* @define Coll `immutable.ParHashSet`
* @define coll immutable parallel hash set
*/
@SerialVersionUID(1L)
class ParHashSet[T] private[immutable] (private[this] val trie: HashSet[T])
extends ParSet[T]
with GenericParTemplate[T, ParHashSet]
with ParSetLike[T, ParHashSet[T], HashSet[T]]
with Serializable
{
self =>
def this() = this(HashSet.empty[T])
override def companion: GenericCompanion[ParHashSet] with GenericParCompanion[ParHashSet] = ParHashSet
override def empty: ParHashSet[T] = new ParHashSet[T]
def splitter: IterableSplitter[T] = new ParHashSetIterator(trie.iterator, trie.size)
override def seq = trie
def -(e: T) = new ParHashSet(trie - e)
def +(e: T) = new ParHashSet(trie + e)
def contains(e: T): Boolean = trie.contains(e)
override def size = trie.size
protected override def reuse[S, That](oldc: Option[Combiner[S, That]], newc: Combiner[S, That]) = oldc match {
case Some(old) => old
case None => newc
}
class ParHashSetIterator(var triter: Iterator[T], val sz: Int)
extends IterableSplitter[T] {
var i = 0
def dup = triter match {
case t: TrieIterator[_] =>
dupFromIterator(t.dupIterator)
case _ =>
val buff = triter.toBuffer
triter = buff.iterator
dupFromIterator(buff.iterator)
}
private def dupFromIterator(it: Iterator[T]) = {
val phit = new ParHashSetIterator(it, sz)
phit.i = i
phit
}
def split: Seq[IterableSplitter[T]] = if (remaining < 2) Seq(this) else triter match {
case t: TrieIterator[_] =>
val previousRemaining = remaining
val ((fst, fstlength), snd) = t.split
val sndlength = previousRemaining - fstlength
Seq(
new ParHashSetIterator(fst, fstlength),
new ParHashSetIterator(snd, sndlength)
)
case _ =>
// iterator of the collision map case
val buff = triter.toBuffer
val (fp, sp) = buff.splitAt(buff.length / 2)
Seq(fp, sp) map { b => new ParHashSetIterator(b.iterator, b.length) }
}
def next(): T = {
i += 1
triter.next()
}
def hasNext: Boolean = {
i < sz
}
def remaining = sz - i
}
}
/** $factoryInfo
* @define Coll `immutable.ParHashSet`
* @define coll immutable parallel hash set
*/
object ParHashSet extends ParSetFactory[ParHashSet] {
def newCombiner[T]: Combiner[T, ParHashSet[T]] = HashSetCombiner[T]
implicit def canBuildFrom[T]: CanCombineFrom[Coll, T, ParHashSet[T]] =
new GenericCanCombineFrom[T]
def fromTrie[T](t: HashSet[T]) = new ParHashSet(t)
}
private[immutable] abstract class HashSetCombiner[T]
extends scala.collection.parallel.BucketCombiner[T, ParHashSet[T], Any, HashSetCombiner[T]](HashSetCombiner.rootsize) {
//self: EnvironmentPassingCombiner[T, ParHashSet[T]] =>
import HashSetCombiner._
val emptyTrie = HashSet.empty[T]
def +=(elem: T) = {
sz += 1
val hc = emptyTrie.computeHash(elem)
val pos = hc & 0x1f
if (buckets(pos) eq null) {
// initialize bucket
buckets(pos) = new UnrolledBuffer[Any]
}
// add to bucket
buckets(pos) += elem
this
}
def result = {
val bucks = buckets.filter(_ != null).map(_.headPtr)
val root = new Array[HashSet[T]](bucks.length)
combinerTaskSupport.executeAndWaitResult(new CreateTrie(bucks, root, 0, bucks.length))
var bitmap = 0
var i = 0
while (i < rootsize) {
if (buckets(i) ne null) bitmap |= 1 << i
i += 1
}
val sz = root.foldLeft(0)(_ + _.size)
if (sz == 0) new ParHashSet[T]
else if (sz == 1) new ParHashSet[T](root(0))
else {
val trie = new HashSet.HashTrieSet(bitmap, root, sz)
new ParHashSet[T](trie)
}
}
/* tasks */
class CreateTrie(bucks: Array[Unrolled[Any]], root: Array[HashSet[T]], offset: Int, howmany: Int)
extends Task[Unit, CreateTrie] {
var result = ()
def leaf(prev: Option[Unit]) = {
var i = offset
val until = offset + howmany
while (i < until) {
root(i) = createTrie(bucks(i))
i += 1
}
}
private def createTrie(elems: Unrolled[Any]): HashSet[T] = {
var trie = new HashSet[T]
var unrolled = elems
var i = 0
while (unrolled ne null) {
val chunkarr = unrolled.array
val chunksz = unrolled.size
while (i < chunksz) {
val v = chunkarr(i).asInstanceOf[T]
val hc = trie.computeHash(v)
trie = trie.updated0(v, hc, rootbits) // internal API, private[collection]
i += 1
}
i = 0
unrolled = unrolled.next
}
trie
}
def split = {
val fp = howmany / 2
List(new CreateTrie(bucks, root, offset, fp), new CreateTrie(bucks, root, offset + fp, howmany - fp))
}
def shouldSplitFurther = howmany > scala.collection.parallel.thresholdFromSize(root.length, combinerTaskSupport.parallelismLevel)
}
}
object HashSetCombiner {
def apply[T] = new HashSetCombiner[T] {} // was: with EnvironmentPassingCombiner[T, ParHashSet[T]] {}
private[immutable] val rootbits = 5
private[immutable] val rootsize = 1 << 5
}
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