smartcore/src/numbers/floatnum.rs

use num_traits::{Float, Signed};

use crate::{numbers::basenum::Number, rand_custom::get_rng_impl};

/// Defines float number
/// <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-AMS_CHTML"></script>
pub trait FloatNumber: Number + Float + Signed {
    /// Copy sign from `sign` - another real number
    fn copysign(self, sign: Self) -> Self;

    /// Calculates natural \\( \ln(1+e^x) \\) without overflow.
    fn ln_1pe(self) -> Self;

    /// Efficient implementation of Sigmoid function, \\( S(x) = \frac{1}{1 + e^{-x}} \\), see [Sigmoid function](https://en.wikipedia.org/wiki/Sigmoid_function)
    fn sigmoid(self) -> Self;

    /// Returns pseudorandom number between 0 and 1
    fn rand() -> Self;

    /// Returns 2
    fn two() -> Self;

    /// Returns .5
    fn half() -> Self;

    /// Returns \\( x^2 \\)
    fn square(self) -> Self {
        self * self
    }

    /// Raw transmutation to u64
    fn to_f32_bits(self) -> u32;
}

impl FloatNumber for f64 {
    fn copysign(self, sign: Self) -> Self {
        self.copysign(sign)
    }

    fn ln_1pe(self) -> f64 {
        if self > 15. {
            self
        } else {
            self.exp().ln_1p()
        }
    }

    fn sigmoid(self) -> f64 {
        if self < -40. {
            0.
        } else if self > 40. {
            1.
        } else {
            1. / (1. + f64::exp(-self))
        }
    }

    fn rand() -> f64 {
        use rand::Rng;
        let mut rng = get_rng_impl(None);
        rng.gen()
    }

    fn two() -> Self {
        2f64
    }

    fn half() -> Self {
        0.5f64
    }

    fn to_f32_bits(self) -> u32 {
        self.to_bits() as u32
    }
}

impl FloatNumber for f32 {
    fn copysign(self, sign: Self) -> Self {
        self.copysign(sign)
    }

    fn ln_1pe(self) -> f32 {
        if self > 15. {
            self
        } else {
            self.exp().ln_1p()
        }
    }

    fn sigmoid(self) -> f32 {
        if self < -40. {
            0.
        } else if self > 40. {
            1.
        } else {
            1. / (1. + f32::exp(-self))
        }
    }

    fn rand() -> f32 {
        use rand::Rng;
        let mut rng = get_rng_impl(None);
        rng.gen()
    }

    fn two() -> Self {
        2f32
    }

    fn half() -> Self {
        0.5f32
    }

    fn to_f32_bits(self) -> u32 {
        self.to_bits()
    }
}