Struct FeatureHistogram 

pub struct FeatureHistogram<'a> {
    pub data: &'a [UnsafeCell<Bin>],
}

Feature Histogram using UnsafeCell for concurrent mutation.

Fields

data: &'a [UnsafeCell<Bin>]

Reference to the histogram data.

Implementations

impl<'a> FeatureHistogram<'a>

pub fn new(hist: &'a mut [Bin]) -> Self

Create a new FeatureHistogram from a mutable slice of bins.

pub unsafe fn update( &self, feature: &[u16], sorted_grad: &[f32], sorted_hess: Option<&[f32]>, index: &[usize], )

Updates the histogram data based on the provided gradients and Hessian values.

Arguments

• feature: A slice of bin indices for each data element.
• sorted_grad: The full gradient array (absolute indexing via index).
• sorted_hess: An optional full Hessian array (absolute indexing via index).
• index: A slice of original indices for the data elements in this node.

Safety

This function is unsafe because it uses get_unchecked and as_mut().unwrap_unchecked(), which bypass Rust’s standard safety checks. The caller must ensure the following:

1. The feature slice must be a valid bin index for every element.
2. All indices in the index slice must be within the bounds of the feature slice.
3. The sorted_grad slice must cover all indices referenced by index.
4. If sorted_hess is Some, it must also cover all indices referenced by index.
5. The internal self.data structure must not be modified externally while this function is running.
6. Each element in self.data must contain a valid Some value that can be mutated.

pub unsafe fn update_cuts(&self, cuts: &[f64])

Updates the cut-off values for the histogram bins.

This function is unsafe because…

Safety

The cuts slice must be sorted in ascending order. The length of cuts must be exactly one less than the number of bins. Calling this function with an unsorted slice or an incorrect length could lead to incorrect binning logic and potential data corruption.

Trait Implementations

impl<'a> Clone for FeatureHistogram<'a>

fn clone(&self) -> FeatureHistogram<'a>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'a> Debug for FeatureHistogram<'a>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'a> Copy for FeatureHistogram<'a>

impl<'a> Send for FeatureHistogram<'a>

impl<'a> Sync for FeatureHistogram<'a>