for {

x := rng.Uint64()

j := int32(x)

i := int(x >> 32 & 255)

if uint32(j+j>>31^j>>31) < normalK[i] {

return float64(j) * float64(normalW[i])

}

if i != 0 {

v := float64(j) * float64(normalW[i])

if (normalF[i] + rng.Float32()*(normalF[i-1]-normalF[i])) < float32(math.Exp(-0.5*v*v)) {

return v

}

} else {

var v float64

for {

// Do 1-x to prevent log(0).

x := -math.Log(1-rng.Float64()) / normalR

y := -math.Log(1 - rng.Float64())

if y+y >= x*x {

v = x + normalR

break

}

}

if x>>63 != 0 {

return -v

}

return v

}

}