Initial project import

tools/v/vlib/math/q_rsqrt.v

@@ -0,0 +1,18 @@
+module math
+
+// q_sqrt computes an approximation of the inverse square root (1 / √x) using a fast
+// inverse square root algorithm. This method is often used in applications
+// where performance is crucial, such as in computer graphics or physics
+// simulations.
+// (This algorithm is inspired by the famous "fast inverse square root" code
+// used in the Quake III Arena game engine.)
+@[inline]
+pub fn q_rsqrt(x f64) f64 {
+	x_half := 0.5 * x
+	mut i := i64(f64_bits(x))
+	i = 0x5fe6eb50c7b537a9 - (i >> 1)
+	mut j := f64_from_bits(u64(i))
+	j *= (1.5 - x_half * j * j)
+	j *= (1.5 - x_half * j * j)
+	return j
+}