From 989c0d0693e27d06d1f70524b66527d1ef12f5a2 Mon Sep 17 00:00:00 2001
From: Stefan Zeiger <szeiger@novocode.com>
Date: Fri, 2 Dec 2011 12:45:40 +0100
Subject: Improve performance of BitSet.size

Using java.lang.Long.bitCount for the size computation is a lot faster
than the previous Scala implementation. Closes SI-2196.
---
 src/library/scala/collection/BitSetLike.scala | 13 +------------
 1 file changed, 1 insertion(+), 12 deletions(-)

(limited to 'src')

diff --git a/src/library/scala/collection/BitSetLike.scala b/src/library/scala/collection/BitSetLike.scala
index 7d9f48f299..e4f9fd436a 100644
--- a/src/library/scala/collection/BitSetLike.scala
+++ b/src/library/scala/collection/BitSetLike.scala
@@ -65,7 +65,7 @@ trait BitSetLike[+This <: BitSetLike[This] with SortedSet[Int]] extends SortedSe
     var i = nwords
     while (i > 0) {
       i -= 1
-      s += popCount(word(i))
+      s += java.lang.Long.bitCount(word(i))
     }
     s
   }
@@ -221,15 +221,4 @@ object BitSetLike {
     else assert(w == 0L)
     newelems
   }
-
-  private val pc1: Array[Int] = {
-    def countBits(x: Int): Int = if (x == 0) 0 else x % 2 + countBits(x >>> 1)
-    Array.tabulate(256)(countBits _)
-  }
-
-  private def popCount(w: Long): Int = {
-    def pc2(w: Int) = if (w == 0) 0 else pc1(w & 0xff) + pc1(w >>> 8)
-    def pc4(w: Int) = if (w == 0) 0 else pc2(w & 0xffff) + pc2(w >>> 16)
-    if (w == 0L) 0 else pc4(w.toInt) + pc4((w >>> 32).toInt)
-  }
 }
-- 
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