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        let is_constant = match_each_native_ptype!(array.ptype(), integral: |$P| {
27            compute_is_constant::<_, {IS_CONST_LANE_WIDTH / size_of::<$P>()}>(array.as_slice::<$P>())
28        } floating_point: |$P| {
29            compute_is_constant::<_, {IS_CONST_LANE_WIDTH / size_of::<$P>()}>(unsafe { std::mem::transmute::<&[$P], &[<$P as EqFloat>::IntType]>(array.as_slice::<$P>()) })
30        });
31
32        Ok(Some(is_constant))
33    }
34}
35
36register_kernel!(IsConstantKernelAdapter(PrimitiveVTable).lift());
37
38// Assumes any floating point has been cast into its bit representation for which != and !is_eq are the same
39// Assumes there's at least 1 value in the slice, which is an invariant of the entry level function.
40pub fn compute_is_constant<T: NativePType, const WIDTH: usize>(values: &[T]) -> bool {
41    let first_value = values[0];
42    let first_vec = &[first_value; WIDTH];
43
44    let mut chunks = values[1..].array_chunks::<WIDTH>();
45    for chunk in &mut chunks {
46        if first_vec != chunk {
47            return false;
48        }
49    }
50
51    for value in chunks.remainder() {
52        if !value.is_eq(first_value) {
53            return false;
54        }
55    }
56
57    true
58}
59
60trait EqFloat {
61    type IntType;
62}
63
64impl EqFloat for f16 {
65    type IntType = u16;
66}
67impl EqFloat for f32 {
68    type IntType = u32;
69}
70impl EqFloat for f64 {
71    type IntType = u64;
72}
vortex_array/arrays/primitive/compute/is_constant.rs

vortex_array/arrays/primitive/compute/
is_constant.rs
