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Reduce allocations of small set/map building #100

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73 changes: 57 additions & 16 deletions src/library/scala/collection/immutable/Map.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -592,42 +592,83 @@ object Map extends ImmutableMapFactory[Map] {
/** Builder for Map.
*/
private final class MapBuilderImpl[K, V] extends mutable.ReusableBuilder[(K,V), Map[K, V]] {
private[this] var k1, k2, k3, k4 = null.asInstanceOf[K]
private[this] var v1, v2, v3, v4 = null.asInstanceOf[V]
private[this] var size = 0

private[this] var elems: Map[K, V] = Map.empty[K, V]
private[this] var switchedToHashMapBuilder: Boolean = false
private[this] var hashMapBuilder: HashMap.HashMapBuilder[K, V] = _

override def clear(): Unit = {
elems =Map.empty[K, V]
if (hashMapBuilder ne null)
hashMapBuilder.clear()
k1 = null.asInstanceOf[K]
k2 = null.asInstanceOf[K]
k3 = null.asInstanceOf[K]
k4 = null.asInstanceOf[K]
v1 = null.asInstanceOf[V]
v2 = null.asInstanceOf[V]
v3 = null.asInstanceOf[V]
v4 = null.asInstanceOf[V]
size = 0
switchedToHashMapBuilder = false
}

override def result(): Map[K, V] =
if (switchedToHashMapBuilder) hashMapBuilder.result() else elems
override def result(): Map[K, V] = size match {
case _ if switchedToHashMapBuilder => hashMapBuilder.result()
case 0 => Map.empty[K, V]
case 1 => new Map1(k1, v1)
case 2 => new Map2(k1, v1, k2, v2)
case 3 => new Map3(k1, v1, k2, v2, k3, v3)
case 4 => new Map4(k1, v1, k2, v2, k3, v3, k4, v4)
}

private def convertToHashMapBuilder(): Unit = {
switchedToHashMapBuilder = true
if (hashMapBuilder eq null)
hashMapBuilder = new HashMap.HashMapBuilder[K, V]

hashMapBuilder ++= elems
hashMapBuilder += ((k1, v1))
hashMapBuilder += ((k2, v2))
hashMapBuilder += ((k3, v3))
hashMapBuilder += ((k4, v4))
}

override def +=(elem: (K, V)): MapBuilderImpl.this.type = {
if (switchedToHashMapBuilder) {
hashMapBuilder += elem
} else if (elems.size < 4) {
elems = elems + elem
} else {
// assert(elems.size == 4)
elems.get(elem._1) match {
case Some(x) if x == elem._2 => ()
case _ =>
convertToHashMapBuilder()
val (k, v) = elem
size match {
case _ if switchedToHashMapBuilder =>
hashMapBuilder += elem
}
case 0 =>
k1 = k; v1 = v; size += 1
case 1 =>
if (k == k1) v1 = v
else {
k2 = k; v2 = v; size += 1
}
case 2 =>
if (k == k1) v2 = v
else if (k == k2) v2 = v
else {
k3 = k; v3 = v; size += 1
}
case 3 =>
if (k == k1) v2 = v
else if (k == k2) v2 = v
else if (k == k3) v3 = v
else {
k4 = k; v4 = v; size += 1
}
case 4 =>
if (k == k1) v2 = v
else if (k == k2) v2 = v
else if (k == k3) v3 = v
else if (k == k4) v4 = v
else {
convertToHashMapBuilder()
hashMapBuilder += elem
size += 1
}
}
this
}
Expand Down
86 changes: 57 additions & 29 deletions src/library/scala/collection/immutable/Set.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -328,45 +328,77 @@ object Set extends ImmutableSetFactory[Set] {
*/
private final class SetBuilderImpl[A] extends mutable.ReusableBuilder[A, Set[A]] {
import scala.collection.immutable.HashSet.HashSetBuilder

private[this] var elems: Set[A] = Set.empty[A]
private[this] var e1, e2, e3, e4 = null.asInstanceOf[A]
private[this] var size = 0
private[this] var switchedToHashSetBuilder: Boolean = false
private[this] var hashSetBuilder: HashSetBuilder[A] = _

override def clear(): Unit = {
elems = Set.empty[A]
if (hashSetBuilder ne null)
hashSetBuilder.clear()
e1 = null.asInstanceOf[A]
e2 = null.asInstanceOf[A]
e3 = null.asInstanceOf[A]
e4 = null.asInstanceOf[A]
size = 0
switchedToHashSetBuilder = false
}

override def result(): Set[A] =
if (switchedToHashSetBuilder) hashSetBuilder.result() else elems

override def +=(elem: A) = {
if (switchedToHashSetBuilder) {
hashSetBuilder += elem
} else if (elems.size < 4) {
elems = elems + elem
} else {
// assert(elems.size == 4)
if (elems.contains(elem)) {
() // do nothing
} else {
convertToHashSetBuilder()
hashSetBuilder += elem
}
}

this
override def result(): Set[A] = size match {
case _ if switchedToHashSetBuilder => hashSetBuilder.result()
case 0 => Set.empty[A]
case 1 => new Set1(e1)
case 2 => new Set2(e1, e2)
case 3 => new Set3(e1, e2, e3)
case 4 => new Set4(e1, e2, e3, e4)
}

private def convertToHashSetBuilder(): Unit = {
switchedToHashSetBuilder = true
if (hashSetBuilder eq null)
hashSetBuilder = new HashSetBuilder
hashSetBuilder = new HashSetBuilder[A]

hashSetBuilder += e1
hashSetBuilder += e2
hashSetBuilder += e3
hashSetBuilder += e4
}

hashSetBuilder ++= elems
override def +=(elem: A): this.type = {
size match {
case _ if switchedToHashSetBuilder =>
hashSetBuilder += elem
case 0 =>
e1 = elem; size += 1
case 1 =>
if (elem == e1) ()
else {
e2 = elem; size += 1
}
case 2 =>
if (elem == e1) ()
else if (elem == e2) ()
else {
e3 = elem; size += 1
}
case 3 =>
if (elem == e1) ()
else if (elem == e2) ()
else if (elem == e3) ()
else {
e4 = elem; size += 1
}
case 4 =>
if (elem == e1) ()
else if (elem == e2) ()
else if (elem == e3) ()
else if (elem == e4) ()
else {
convertToHashSetBuilder()
hashSetBuilder += elem
size += 1
}
}
this
}

override def ++=(xs: TraversableOnce[A]): this.type = {
Expand All @@ -382,9 +414,5 @@ object Set extends ImmutableSetFactory[Set] {
}
this
}

}


}