rustnum 0.1.0

NumPy-style n-dimensional arrays for Rust: one array type, NumPy names, pure 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
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156

pub(crate) fn size(shape: &[usize]) -> usize {
    if shape.contains(&0) {
        return 0;
    }
    shape
        .iter()
        .try_fold(1usize, |n, &d| n.checked_mul(d))
        .expect("array is too big")
}
pub(crate) fn strides(shape: &[usize]) -> Vec<isize> {
    let mut out = vec![0; shape.len()];
    let mut n = 1isize;
    for (i, &d) in shape.iter().enumerate().rev() {
        out[i] = n;
        n = n
            .checked_mul(isize::try_from(d).expect("array is too big"))
            .expect("array is too big");
    }
    out
}
pub(crate) fn contiguous(shape: &[usize], st: &[isize]) -> bool {
    if shape.contains(&0) {
        return true;
    }
    let mut expected = 1;
    for (&d, &s) in shape.iter().zip(st).rev() {
        if d > 1 && s != expected {
            return false;
        }
        expected *= d as isize;
    }
    true
}
// Common ranks stay on the stack; arbitrary rank remains supported.
struct Axes<T: Copy + Default> {
    inline: [T; 8],
    spill: Vec<T>,
    len: usize,
}
impl<T: Copy + Default> Axes<T> {
    fn new(values: &[T]) -> Self {
        let mut out = Self {
            inline: [T::default(); 8],
            spill: Vec::new(),
            len: values.len(),
        };
        if values.len() <= 8 {
            out.inline[..values.len()].copy_from_slice(values);
        } else {
            out.spill = values.to_vec();
        }
        out
    }
    fn zeros(len: usize) -> Self {
        Self {
            inline: [T::default(); 8],
            spill: if len > 8 {
                vec![T::default(); len]
            } else {
                Vec::new()
            },
            len,
        }
    }
}
impl<T: Copy + Default> std::ops::Deref for Axes<T> {
    type Target = [T];
    fn deref(&self) -> &[T] {
        if self.len <= 8 {
            &self.inline[..self.len]
        } else {
            &self.spill
        }
    }
}
impl<T: Copy + Default> std::ops::DerefMut for Axes<T> {
    fn deref_mut(&mut self) -> &mut [T] {
        if self.len <= 8 {
            &mut self.inline[..self.len]
        } else {
            &mut self.spill
        }
    }
}
pub(crate) struct Offsets {
    shape: Axes<usize>,
    strides: Axes<isize>,
    coord: Axes<usize>,
    offset: isize,
    left: usize,
}
impl Offsets {
    pub(crate) fn new(shape: &[usize], strides: &[isize], offset: usize) -> Self {
        Self {
            shape: Axes::new(shape),
            strides: Axes::new(strides),
            coord: Axes::zeros(shape.len()),
            offset: offset as isize,
            left: size(shape),
        }
    }
}
impl Iterator for Offsets {
    type Item = usize;
    fn next(&mut self) -> Option<usize> {
        if self.left == 0 {
            return None;
        }
        let out = self.offset as usize;
        self.left -= 1;
        if self.left > 0 {
            for i in (0..self.shape.len()).rev() {
                self.coord[i] += 1;
                if self.coord[i] < self.shape[i] {
                    self.offset += self.strides[i];
                    break;
                }
                self.coord[i] = 0;
                self.offset -= self.strides[i] * (self.shape[i] as isize - 1);
            }
        }
        Some(out)
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        (self.left, Some(self.left))
    }
}
impl ExactSizeIterator for Offsets {}
pub(crate) fn advance(coord: &mut [usize], shape: &[usize]) {
    for i in (0..shape.len()).rev() {
        coord[i] += 1;
        if coord[i] < shape[i] {
            break;
        }
        coord[i] = 0;
    }
}
#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn reverse_offsets() {
        assert_eq!(
            Offsets::new(&[2, 3], &[3, -1], 2).collect::<Vec<_>>(),
            [2, 1, 0, 5, 4, 3]
        );
    }
    #[test]
    fn singleton_contiguity() {
        assert!(contiguous(&[2, 1, 3], &[3, 0, 1]));
    }
    #[test]
    fn empty_offsets() {
        assert_eq!(Offsets::new(&[0], &[-1], 0).next(), None);
    }
}