.

[SXSI/XMLTree.git] / libcds / src / basics.h

diff --git a/libcds/src/basics.h b/libcds/src/basics.h
index 4e00cae..3376902 100644 (file)
--- a/libcds/src/basics.h
+++ b/libcds/src/basics.h
@@ -233,6 +233,20 @@ inline uint popcount(int x){
   return __popcount_tab[(x >>  0) & 0xff]  + __popcount_tab[(x >>  8) & 0xff]
           + __popcount_tab[(x >> 16) & 0xff] + __popcount_tab[(x >> 24) & 0xff];
 }
+inline unsigned int
+fast_popcount(int x)
+{
+    uint m1 = 0x55555555;
+    uint m2 = 0x33333333;
+    uint m4 = 0x0f0f0f0f;
+    x -= (x >> 1) & m1;
+    x = (x & m2) + ((x >> 2) & m2);
+    x = (x + (x >> 4)) & m4;
+    x += x >>  8;
+    return (x + (x >> 16)) & 0x3f;
+}
+
+
 
 /** Counts the number of 1s in the first 16 bits of x */
 inline uint popcount16(int x){