Improve efficiency of updated

Added utility method to create a HashTrieSet with two leaf HashSets with different hash
Used said utility method instead of creating a temorary HashTrieSet with an empty elems array
Added assertions to HashTrieSet to validate tree

1 files changed, 29 insertions, 10 deletions

diff --git a/src/library/scala/collection/immutable/HashSet.scala b/src/library/scala/collection/immutable/HashSet.scala
index ef0173337c..d9ce7a68f7 100644
--- a/src/library/scala/collection/immutable/HashSet.scala
+++ b/src/library/scala/collection/immutable/HashSet.scala
@@ -102,6 +102,30 @@ object HashSet extends ImmutableSetFactory[HashSet] {
 
   private object EmptyHashSet extends HashSet[Any] { }
 
+  // utility method to create a HashTrieSet from two leaf HashSets (HashSet1 or HashSetCollision1) with non-colliding hash code)
+  private def makeHashTrieSet[A](hash0:Int, elem0:HashSet[A], hash1:Int, elem1:HashSet[A], level:Int) : HashTrieSet[A] = {
+    val index0 = (hash0 >>> level) & 0x1f
+    val index1 = (hash1 >>> level) & 0x1f
+    if(index0 != index1) {
+      val bitmap = (1 << index0) | (1 << index1)
+      val elems = new Array[HashSet[A]](2)
+      if(index0 < index1) {
+        elems(0) = elem0
+        elems(1) = elem1
+      } else {
+        elems(0) = elem1
+        elems(1) = elem0
+      }
+      new HashTrieSet[A](bitmap, elems, elem0.size + elem1.size)
+    } else {
+      val elems = new Array[HashSet[A]](1)
+      val bitmap = (1 << index0)
+      val child = makeHashTrieSet(hash0, elem0, hash1, elem1, level + 5)
+      elems(0) = child
+      new HashTrieSet[A](bitmap, elems, child.size)
+    }
+  }
+
   // TODO: add HashSet2, HashSet3, ...
 
   class HashSet1[A](private[HashSet] val key: A, private[HashSet] val hash: Int) extends HashSet[A] {
@@ -114,9 +138,7 @@ object HashSet extends ImmutableSetFactory[HashSet] {
       if (hash == this.hash && key == this.key) this
       else {
         if (hash != this.hash) {
-          //new HashTrieSet[A](level+5, this, new HashSet1(key, hash))
-          val m = new HashTrieSet[A](0,new Array[HashSet[A]](0),0) // TODO: could save array alloc
-          m.updated0(this.key, this.hash, level).updated0(key, hash, level)
+          makeHashTrieSet(this.hash, this, hash, new HashSet1(key, hash), level)
         } else {
           // 32-bit hash collision (rare, but not impossible)
           new HashSetCollision1(hash, ListSet.empty + this.key + key)
@@ -140,13 +162,7 @@ object HashSet extends ImmutableSetFactory[HashSet] {
 
     override def updated0(key: A, hash: Int, level: Int): HashSet[A] =
       if (hash == this.hash) new HashSetCollision1(hash, ks + key)
-      else {
-        var m: HashSet[A] = new HashTrieSet[A](0,new Array[HashSet[A]](0),0)
-        // might be able to save some ops here, but it doesn't seem to be worth it
-        for (k <- ks)
-          m = m.updated0(k, this.hash, level)
-        m.updated0(key, hash, level)
-      }
+      else makeHashTrieSet(this.hash, this, hash, new HashSet1(key, hash), level)
 
     override def removed0(key: A, hash: Int, level: Int): HashSet[A] =
       if (hash == this.hash) {
@@ -181,6 +197,9 @@ object HashSet extends ImmutableSetFactory[HashSet] {
 
   class HashTrieSet[A](private val bitmap: Int, private[collection] val elems: Array[HashSet[A]], private val size0: Int)
         extends HashSet[A] {
+    assert(Integer.bitCount(bitmap) == elems.length)
+    // assertion has to remain disabled until SI-6197 is solved
+    // assert(elems.length > 1 || (elems.length == 1 && elems(0).isInstanceOf[HashTrieSet[_]]))
 
     override def size = size0