math: optimize sinh and cosh

Improve performance by reducing unnecessary function calls Benchmarks: Tme old time/op new time/op delta Cosh-8 229ns ± 0% 138ns ± 0% -39.74% (p=0.008 n=5+5) Sinh-8 231ns ± 0% 139ns ± 0% -39.83% (p=0.008 n=5+5) Change-Id: Icab5485849bbfaafca8429d06b67c558101f4f3c Reviewed-on: https://go-review.googlesource.com/85477 Reviewed-by: Robert Griesemer <[email protected]>
golang · Feb 27, 2018 · ed6c6c9 · ed6c6c9
1 parent 486caa2
commit ed6c6c9
Showing 1 changed file with 6 additions and 4 deletions.
diff --git a/src/math/sinh.go b/src/math/sinh.go
@@ -45,10 +45,11 @@ func sinh(x float64) float64 {
 	var temp float64
 	switch true {
 	case x > 21:
-		temp = Exp(x) / 2
+		temp = Exp(x) * 0.5
 
 	case x > 0.5:
-		temp = (Exp(x) - Exp(-x)) / 2
+		ex := Exp(x)
+		temp = (ex - 1/ex) * 0.5
 
 	default:
 		sq := x * x
@@ -73,7 +74,8 @@ func Cosh(x float64) float64
 func cosh(x float64) float64 {
 	x = Abs(x)
 	if x > 21 {
-		return Exp(x) / 2
+		return Exp(x) * 0.5
 	}
-	return (Exp(x) + Exp(-x)) / 2
+	ex := Exp(x)
+	return (ex + 1/ex) * 0.5
 }