candle_core_temp/
strided_index.rs

1use crate::Layout;
2
3/// An iterator over offset position for items of an N-dimensional arrays stored in a
4/// flat buffer using some potential strides.
5#[derive(Debug)]
6pub struct StridedIndex<'a> {
7    next_storage_index: Option<usize>,
8    multi_index: Vec<usize>,
9    dims: &'a [usize],
10    stride: &'a [usize],
11}
12
13impl<'a> StridedIndex<'a> {
14    pub(crate) fn new(dims: &'a [usize], stride: &'a [usize], start_offset: usize) -> Self {
15        let elem_count: usize = dims.iter().product();
16        let next_storage_index = if elem_count == 0 {
17            None
18        } else {
19            // This applies to the scalar case.
20            Some(start_offset)
21        };
22        StridedIndex {
23            next_storage_index,
24            multi_index: vec![0; dims.len()],
25            dims,
26            stride,
27        }
28    }
29
30    pub(crate) fn from_layout(l: &'a Layout) -> Self {
31        Self::new(l.dims(), l.stride(), l.start_offset())
32    }
33}
34
35impl<'a> Iterator for StridedIndex<'a> {
36    type Item = usize;
37
38    fn next(&mut self) -> Option<Self::Item> {
39        let storage_index = match self.next_storage_index {
40            None => return None,
41            Some(storage_index) => storage_index,
42        };
43        let mut updated = false;
44        let mut next_storage_index = storage_index;
45        for ((multi_i, max_i), stride_i) in self
46            .multi_index
47            .iter_mut()
48            .zip(self.dims.iter())
49            .zip(self.stride.iter())
50            .rev()
51        {
52            let next_i = *multi_i + 1;
53            if next_i < *max_i {
54                *multi_i = next_i;
55                updated = true;
56                next_storage_index += stride_i;
57                break;
58            } else {
59                next_storage_index -= *multi_i * stride_i;
60                *multi_i = 0
61            }
62        }
63        self.next_storage_index = if updated {
64            Some(next_storage_index)
65        } else {
66            None
67        };
68        Some(storage_index)
69    }
70}
71
72#[derive(Debug)]
73pub enum StridedBlocks<'a> {
74    SingleBlock {
75        start_offset: usize,
76        len: usize,
77    },
78    MultipleBlocks {
79        block_start_index: StridedIndex<'a>,
80        block_len: usize,
81    },
82}
candle_core_temp/strided_index.rs

candle_core_temp/
strided_index.rs
