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