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package scala.collection.parallel.immutable
import scala.collection.parallel.ParMap
import scala.collection.parallel.ParMapLike
import scala.collection.parallel.Combiner
import scala.collection.parallel.ParIterableIterator
import scala.collection.parallel.EnvironmentPassingCombiner
import scala.collection.parallel.Unrolled
import scala.collection.generic.ParMapFactory
import scala.collection.generic.CanCombineFrom
import scala.collection.generic.GenericParMapTemplate
import scala.collection.generic.GenericParMapCompanion
import scala.collection.immutable.HashMap
/** Parallel hash trie map.
*
* @author prokopec
*/
class ParHashMap[K, +V] private[immutable] (private[this] val trie: HashMap[K, V])
extends ParMap[K, V]
with GenericParMapTemplate[K, V, ParHashMap]
with ParMapLike[K, V, ParHashMap[K, V], HashMap[K, V]]
{
self =>
def this() = this(HashMap.empty[K, V])
override def mapCompanion: GenericParMapCompanion[ParHashMap] = ParHashMap
override def empty: ParHashMap[K, V] = new ParHashMap[K, V]
def parallelIterator: ParIterableIterator[(K, V)] = new ParHashMapIterator(trie.iterator, trie.size) with SCPI
def seq = trie
def -(k: K) = new ParHashMap(trie - k)
def +[U >: V](kv: (K, U)) = new ParHashMap(trie + kv)
def get(k: K) = trie.get(k)
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
}
type SCPI = SignalContextPassingIterator[ParHashMapIterator]
class ParHashMapIterator(val triter: Iterator[(K, V)], val sz: Int)
extends super.ParIterator {
self: SignalContextPassingIterator[ParHashMapIterator] =>
var i = 0
def split: Seq[ParIterator] = if (remaining < 2) Seq(this) else triter match {
case t: HashMap.TrieIterator[_, _] =>
val previousRemaining = remaining
val ((fst, fstlength), snd) = t.asInstanceOf[HashMap.TrieIterator[K, V]].split
val sndlength = previousRemaining - fstlength
Seq(
new ParHashMapIterator(fst, fstlength) with SCPI,
new ParHashMapIterator(snd, sndlength) with SCPI
)
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 ParHashMapIterator(b.iterator, b.length) with SCPI }
}
def next: (K, V) = {
i += 1
triter.next
}
def hasNext: Boolean = {
i < sz
}
def remaining = sz - i
}
}
object ParHashMap extends ParMapFactory[ParHashMap] {
def empty[K, V]: ParHashMap[K, V] = new ParHashMap[K, V]
def newCombiner[K, V]: Combiner[(K, V), ParHashMap[K, V]] = HashMapCombiner[K, V]
implicit def canBuildFrom[K, V]: CanCombineFrom[Coll, (K, V), ParHashMap[K, V]] = {
new CanCombineFromMap[K, V]
}
def fromTrie[K, V](t: HashMap[K, V]) = new ParHashMap(t)
var totalcombines = new java.util.concurrent.atomic.AtomicInteger(0)
}
private[immutable] abstract class HashMapCombiner[K, V]
extends collection.parallel.BucketCombiner[(K, V), ParHashMap[K, V], (K, V), HashMapCombiner[K, V]](HashMapCombiner.rootsize) {
self: EnvironmentPassingCombiner[(K, V), ParHashMap[K, V]] =>
import HashMapCombiner._
def +=(elem: (K, V)) = {
sz += 1
val hc = elem._1.##
val pos = hc & 0x1f
if (lasts(pos) eq null) {
// initialize bucket
heads(pos) = new Unrolled[(K, V)]
lasts(pos) = heads(pos)
}
// add to bucket
lasts(pos) = lasts(pos).add(elem)
this
}
def result = {
val buckets = heads.filter(_ != null)
val root = new Array[HashMap[K, V]](buckets.length)
executeAndWaitResult(new CreateTrie(buckets, root, 0, buckets.length))
var bitmap = 0
var i = 0
while (i < rootsize) {
if (heads(i) ne null) bitmap |= 1 << i
i += 1
}
val sz = root.foldLeft(0)(_ + _.size)
if (sz == 0) new ParHashMap[K, V]
else if (sz == 1) new ParHashMap[K, V](root(0))
else {
val trie = new HashMap.HashTrieMap(bitmap, root, sz)
new ParHashMap[K, V](trie)
}
}
/* tasks */
class CreateTrie(buckets: Array[Unrolled[(K, V)]], root: Array[HashMap[K, V]], offset: Int, howmany: Int) extends super.Task[Unit, CreateTrie] {
var result = ()
def leaf(prev: Option[Unit]) = {
var i = offset
val until = offset + howmany
while (i < until) {
root(i) = createTrie(buckets(i))
i += 1
}
}
private def createTrie(elems: Unrolled[(K, V)]): HashMap[K, V] = {
var trie = new HashMap[K, V]
var unrolled = elems
var i = 0
while (unrolled ne null) {
val chunkarr = unrolled.array
val chunksz = unrolled.size
while (i < chunksz) {
val kv = chunkarr(i)
val hc = kv._1.##
trie = trie.updated0(kv._1, hc, rootbits, kv._2, kv, null)
i += 1
}
i = 0
unrolled = unrolled.next
}
trie
}
def split = {
val fp = howmany / 2
List(new CreateTrie(buckets, root, offset, fp), new CreateTrie(buckets, root, offset + fp, howmany - fp))
}
def shouldSplitFurther = howmany > collection.parallel.thresholdFromSize(root.length, parallelismLevel)
}
}
private[parallel] object HashMapCombiner {
def apply[K, V] = new HashMapCombiner[K, V] with EnvironmentPassingCombiner[(K, V), ParHashMap[K, V]]
private[immutable] val rootbits = 5
private[immutable] val rootsize = 1 << 5
}
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