From 92f2d6880204666b2e4c786108eaf8a7432a4279 Mon Sep 17 00:00:00 2001
From: Brent Pedersen <bpederse@gmail.com>
Date: Mon, 9 Sep 2019 14:04:28 -0600
Subject: count 64 bits at a time

---
 lib/system/sets.nim | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

(limited to 'lib/system/sets.nim')

diff --git a/lib/system/sets.nim b/lib/system/sets.nim
index e48484da7..fe7df053d 100644
--- a/lib/system/sets.nim
+++ b/lib/system/sets.nim
@@ -21,7 +21,7 @@ proc countBits32(n: uint32): int {.compilerproc.} =
   v = (v and 0x33333333) + ((v shr 2) and 0x33333333)
   result = (((v + (v shr 4) and 0xF0F0F0F) * 0x1010101) shr 24).int
 
-proc countBits64(n: uint64): int {.compilerproc.} =
+proc countBits64(n: uint64): int {.compilerproc, inline.} =
   # generic formula is from: https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
   var v = uint64(n)
   v = v - ((v shr 1'u64) and 0x5555555555555555'u64)
@@ -30,6 +30,10 @@ proc countBits64(n: uint64): int {.compilerproc.} =
   result = ((v * 0x0101010101010101'u64) shr 56'u64).int
 
 proc cardSet(s: NimSet, len: int): int {.compilerproc, inline.} =
-  for i in 0..<len:
-    if likely(s[i] == 0): continue
+  var j = -1
+  for i in countup(0, len - 8, 8):
+    inc(result, countBits64((cast[ptr uint64](s[i].unsafeAddr))[]))
+    j = i + 7
+
+  for i in (j+1)..<len:
     inc(result, countBits32(uint32(s[i])))
-- 
cgit 1.4.1-2-gfad0