aegir 2.0.0

Strongly-typed, reverse-mode autodiff library in Rust
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136

use super::{
    shapes::{Shaped, S0},
    Buffer,
    Class,
    IncompatibleShapes,
    ZipFold,
    ZipMap,
};
use num_traits::Num;

/// Scalar buffer class.
pub struct Scalars;

impl Class<S0> for Scalars {
    type Buffer<F: Scalar> = F;

    fn build<F: Scalar>(_: S0, f: impl Fn(()) -> F) -> F { f(()) }

    fn build_subset<F: Scalar>(
        shape: S0,
        base: F,
        mut indices: impl Iterator<Item = ()>,
        active: impl Fn(()) -> F,
    ) -> F {
        let next = indices.next();

        if next.is_some() {
            Self::full(shape, active(()))
        } else {
            Self::full(shape, base)
        }
    }
}

/// Trait for numeric types implementing basic scalar operations.
pub trait Scalar:
    Copy + Num + Buffer<Class = Scalars, Shape = S0, Field = Self> + ZipMap<Self> + ZipFold<Self>
{
}

macro_rules! impl_scalar {
    ($F:ty) => {
        impl Shaped for $F {
            type Shape = S0;

            fn shape(&self) -> S0 { S0 }
        }

        impl Buffer for $F {
            type Class = Scalars;
            type Field = $F;

            fn class() -> Scalars { Scalars }

            fn get(&self, _: ()) -> Option<$F> { Some(*self) }

            fn get_unchecked(&self, _: ()) -> $F { *self }

            fn map<F: Scalar, M: Fn($F) -> F>(self, f: M) -> F { f(self) }

            fn map_ref<F: Scalar, M: Fn($F) -> F>(&self, f: M) -> F { f(*self) }

            fn mutate<M: Fn($F) -> $F>(&mut self, f: M) { *self = f(*self); }

            fn fold<F, M: Fn(F, $F) -> F>(&self, init: F, f: M) -> F { f(init, *self) }
        }

        impl ZipFold for $F {
            fn zip_fold<A: Scalar, M: Fn(A, ($F, $F)) -> A>(
                &self,
                rhs: &$F,
                init: A,
                f: M,
            ) -> Result<A, IncompatibleShapes<S0>> {
                let out = f(init, (*self, *rhs));

                Ok(out)
            }
        }

        impl ZipMap for $F {
            type Output<A: Scalar> = A;

            #[inline]
            fn zip_map<A: Scalar, M: Fn($F, $F) -> A>(
                self,
                rhs: &$F,
                f: M,
            ) -> Result<A, IncompatibleShapes<S0>> {
                Ok(f(self, *rhs))
            }

            #[inline]
            fn zip_shape(
                self,
                _: S0,
            ) -> Result<Self, IncompatibleShapes<S0>> {
                Ok(self)
            }
        }

        impl Scalar for $F {}
    };
}

impl_scalar!(f32);
impl_scalar!(f64);

impl_scalar!(u8);
impl_scalar!(u16);
impl_scalar!(u32);
impl_scalar!(u64);
impl_scalar!(usize);

impl_scalar!(i8);
impl_scalar!(i16);
impl_scalar!(i32);
impl_scalar!(i64);
impl_scalar!(isize);

#[cfg(test)]
mod tests {
    use super::*;

    mod f64 {
        use super::*;

        #[test]
        fn test_field() {
            assert_eq!(1.0 + 2.0, 3.0);
            assert_eq!(1.0 - 2.0, -1.0);
            assert_eq!(1.0 * 2.0, 2.0);
            assert_eq!(1.0 / 2.0, 0.5);
        }
    }
}