shawnsmithdev · January 1, 2021 00:46 · Jan 1, 2021
diff --git a/qrsqrt.go b/qrsqrt.go
@@ -0,0 +1,23 @@
+// This is the Quake III Q_rsqrt Fast Approx Inverse Square Root algorithm
+
+package main
+
+import (
+	"fmt"
+	"math"
+)
+
+const threehalfs float32 = 1.5
+
+func qrsqrt(number float32) float32 {
+	i := math.Float32bits(number)
+	i = 0x5f3759df - (i >> 1)
+	y := math.Float32frombits(i)
+
+	x2 := number * 0.5
+	return y * (threehalfs - (x2 * y * y))
+}
+
+func main() {
+	fmt.Println(qrsqrt(27)) // prints 0.19215362 for 0.154% error
+}