mirror of
https://github.com/make-42/xyosc
synced 2024-11-23 01:30:09 +01:00
28 lines
982 B
Go
28 lines
982 B
Go
|
package fastsqrt
|
||
|
|
|
||
|
|
import "math"
|
||
|
|
|
||
|
|
const magic32 = 0x5F375A86
|
||
|
|
|
||
|
|
func FastInvSqrt32(n float32) float32 {
|
||
|
|
// If n is negative return NaN
|
||
|
|
if n < 0 {
|
||
|
|
return float32(math.NaN())
|
||
|
|
} // n2 and th are for one iteration of Newton's method later
|
||
|
|
n2, th := n*0.5, float32(1.5) // Use math.Float32bits to represent the float32, n, as
|
||
|
|
// an uint32 without modification.
|
||
|
|
b := math.Float32bits(n) // Use the new uint32 view of the float32 to shift the bits
|
||
|
|
// of the float32 1 to the right, chopping off 1 bit from
|
||
|
|
// the fraction part of the float32.
|
||
|
|
b = magic32 - (b >> 1) // Use math.Float32frombits to convert the uint32 bits back
|
||
|
|
// into their float32 representation, again no actual change
|
||
|
|
// in the bits, just a change in how we treat them in memory.
|
||
|
|
// f is now our answer of 1 / sqrt(n)
|
||
|
|
f := math.Float32frombits(b) // Perform one iteration of Newton's method on f to improve
|
||
|
|
// accuracy
|
||
|
|
f *= th - (n2 * f * f)
|
||
|
|
|
||
|
|
// And return our fast inverse square root result
|
||
|
|
return f
|
||
|
|
}
|