Trait Splitter 

pub trait Splitter {
    // Required methods
    fn get_constraint(&self, feature: &usize) -> Option<&Constraint>;
    fn get_gamma(&self) -> f32;
    fn get_l1(&self) -> f32;
    fn get_l2(&self) -> f32;
    fn get_max_delta_step(&self) -> f32;
    fn get_learning_rate(&self) -> f32;
    fn evaluate_split(
        &self,
        left_gradient: f32,
        left_hessian: f32,
        right_gradient: f32,
        right_hessian: f32,
        missing_gradient: f32,
        missing_hessian: f32,
        lower_bound: f32,
        upper_bound: f32,
        parent_weight: f32,
        constraint: Option<&Constraint>,
    ) -> Option<(NodeInfo, NodeInfo, MissingInfo)>;
    fn handle_split_info(
        &self,
        split_info: SplitInfo,
        n_nodes: &usize,
        node: &mut SplittableNode,
        index: &mut [usize],
        col_index: &[usize],
        data: &Matrix<'_, u16>,
        cuts: &JaggedMatrix<f64>,
        grad: &[f32],
        hess: &[f32],
        parallel: bool,
    ) -> Vec<SplittableNode>;

    // Provided methods
    fn new_leaves_added(&self) -> usize { ... }
    fn clean_up_splits(&self, _tree: &mut Tree) { ... }
    fn best_split(
        &self,
        node: &SplittableNode,
        col_index: &[usize],
    ) -> Option<SplitInfo> { ... }
    fn best_feature_split(
        &self,
        node: &SplittableNode,
        feature: usize,
        idx: usize,
    ) -> Option<SplitInfo> { ... }
    fn split_node(
        &self,
        n_nodes: &usize,
        node: &mut SplittableNode,
        index: &mut [usize],
        col_index: &[usize],
        data: &Matrix<'_, u16>,
        cuts: &JaggedMatrix<f64>,
        grad: &[f32],
        hess: &[f32],
        parallel: bool,
    ) -> Vec<SplittableNode> { ... }
}

Required Methods

fn get_constraint(&self, feature: &usize) -> Option<&Constraint>

fn get_gamma(&self) -> f32

fn get_l1(&self) -> f32

fn get_l2(&self) -> f32

fn get_max_delta_step(&self) -> f32

fn get_learning_rate(&self) -> f32

fn evaluate_split( &self, left_gradient: f32, left_hessian: f32, right_gradient: f32, right_hessian: f32, missing_gradient: f32, missing_hessian: f32, lower_bound: f32, upper_bound: f32, parent_weight: f32, constraint: Option<&Constraint>, ) -> Option<(NodeInfo, NodeInfo, MissingInfo)>

Evaluate a split, returning the node info for the left, and right splits, as well as the node info the missing data of a feature.

fn handle_split_info( &self, split_info: SplitInfo, n_nodes: &usize, node: &mut SplittableNode, index: &mut [usize], col_index: &[usize], data: &Matrix<'_, u16>, cuts: &JaggedMatrix<f64>, grad: &[f32], hess: &[f32], parallel: bool, ) -> Vec<SplittableNode>

Handle the split info, creating the children nodes, this function will return a vector of new splitable nodes, that can be added to the growable stack, and further split, or converted to leaf nodes.

Provided Methods

fn new_leaves_added(&self) -> usize

When a split happens, how many leaves will the tree increase by? For example, if a binary split happens, the split will increase the number of leaves by 1, if a ternary split happens, the number of leaves will increase by 2.

fn clean_up_splits(&self, _tree: &mut Tree)

Perform any post processing on the tree that is relevant for the specific splitter, empty default implementation so that it can be called even if it’s not used.

fn best_split( &self, node: &SplittableNode, col_index: &[usize], ) -> Option<SplitInfo>

Find the best possible split, considering all feature histograms. If we wanted to add Column sampling, this is probably where we would need to do it, otherwise, it would be at the tree level.

fn best_feature_split( &self, node: &SplittableNode, feature: usize, idx: usize, ) -> Option<SplitInfo>

The idx is the index of the feature in the histogram data, whereas feature is the index of the actual feature in the data.

fn split_node( &self, n_nodes: &usize, node: &mut SplittableNode, index: &mut [usize], col_index: &[usize], data: &Matrix<'_, u16>, cuts: &JaggedMatrix<f64>, grad: &[f32], hess: &[f32], parallel: bool, ) -> Vec<SplittableNode>

Split the node, if we cant find a best split, we will need to return an empty vector, this node is a leaf.

Implementors

impl Splitter for MissingBranchSplitter

impl Splitter for MissingImputerSplitter