day 85: big perf boost from 10k ns/op to 522 ns/op

vaskoz · Nov 14, 2018 · 439ba1c · 439ba1c
1 parent af82d65
commit 439ba1c
Showing 1 changed file with 6 additions and 3 deletions.
diff --git a/day85/problem.go b/day85/problem.go
@@ -3,9 +3,12 @@ package day85
 // MathematicalIf returns x if b=1 and y if b=0.
 func MathematicalIf(x, y, b int32) int32 {
 	var xMask, yMask int32
-	for i := uint32(0); i < 32; i++ {
-		xMask |= b << i
-	}
+	xMask = b
+	xMask |= xMask << 1
+	xMask |= xMask << 2
+	xMask |= xMask << 4
+	xMask |= xMask << 8
+	xMask |= xMask << 16
 	yMask = ^xMask
 	return (x & xMask) | (y & yMask)
 }