vortex_array/arrays/primitive/compute/
is_constant.rs

1use vortex_dtype::half::f16;
2use vortex_dtype::{NativePType, match_each_native_ptype};
3use vortex_error::VortexResult;
4
5use crate::arrays::{PrimitiveArray, PrimitiveVTable};
6use crate::compute::{IsConstantKernel, IsConstantKernelAdapter, IsConstantOpts};
7use crate::register_kernel;
8
9cfg_if::cfg_if! {
10    if #[cfg(target_feature = "avx2")] {
11        pub const IS_CONST_LANE_WIDTH: usize = 32;
12    } else {
13        pub const IS_CONST_LANE_WIDTH: usize = 16;
14    }
15}
16
17impl IsConstantKernel for PrimitiveVTable {
18    fn is_constant(
19        &self,
20        array: &PrimitiveArray,
21        opts: &IsConstantOpts,
22    ) -> VortexResult<Option<bool>> {
23        if opts.is_negligible_cost() {
24            return Ok(None);
25        }
26
27        let is_constant = match_each_native_ptype!(array.ptype(), integral: |P| {
28            compute_is_constant::<_, {IS_CONST_LANE_WIDTH / size_of::<P>()}>(array.as_slice::<P>())
29        }, floating_point: |P| {
30            compute_is_constant::<_, {IS_CONST_LANE_WIDTH / size_of::<P>()}>(unsafe { std::mem::transmute::<&[P], &[<P as EqFloat>::IntType]>(array.as_slice::<P>()) })
31        });
32
33        Ok(Some(is_constant))
34    }
35}
36
37register_kernel!(IsConstantKernelAdapter(PrimitiveVTable).lift());
38
39/// Assumes any floating point has been cast into its bit representation for which != and !is_eq are the same
40/// Assumes there's at least 1 value in the slice, which is an invariant of the entry level function.
41pub fn compute_is_constant<T: NativePType, const WIDTH: usize>(values: &[T]) -> bool {
42    let first_value = values[0];
43    let first_vec = &[first_value; WIDTH];
44
45    let mut chunks = values[1..].chunks_exact(WIDTH);
46    for chunk in &mut chunks {
47        assert_eq!(chunk.len(), WIDTH); // let the compiler know each chunk is WIDTH.
48        if first_vec != chunk {
49            return false;
50        }
51    }
52
53    for value in chunks.remainder() {
54        if !value.is_eq(first_value) {
55            return false;
56        }
57    }
58
59    true
60}
61
62trait EqFloat {
63    type IntType;
64}
65
66impl EqFloat for f16 {
67    type IntType = u16;
68}
69impl EqFloat for f32 {
70    type IntType = u32;
71}
72impl EqFloat for f64 {
73    type IntType = u64;
74}
vortex_array/arrays/primitive/compute/is_constant.rs

vortex_array/arrays/primitive/compute/
is_constant.rs
