Enum PfxTree 

pub enum PfxTree {
    Branch(Arc<IndexMap<Pfx, PfxTree>>),
    Leaf(usize),
}

A tree structure for generating unique prefix keys.

The tree width is determined by the number of logprobs the LLM generates. For flat structures (`A`, `B`), each leaf corresponds to one logprob slot. For large response sets exceeding the logprobs limit, nested structures (`A` `A`, `A` `B`) allow capturing preferences in stages.

Variants

Branch(Arc<IndexMap<Pfx, PfxTree>>)

A branch containing child nodes.

Leaf(usize)

A leaf containing the response index.

Implementations

impl PfxTree

pub fn new(rng: &mut impl Rng, source_len: usize, max_branch_len: usize) -> Self

Creates a new prefix tree for the given number of responses.

The max_branch_len should match the number of logprobs the LLM generates, ensuring each branch fits within one logprobs batch for probability capture.

pub fn new_inner( rng: &mut impl Rng, source: &[usize], max_branch_len: usize, force_sub_branch: bool, ) -> Self

Internal recursive constructor.

pub fn pfx_indices( &self, rng: &mut impl Rng, source_len: usize, ) -> Vec<(String, usize)>

Generates prefix-to-index mappings in randomized order.

Returns pairs of (prefix key, response index).

pub fn pfx_indices_inner( &self, parent_pfx: Option<String>, indices: &mut Vec<(String, usize)>, )

Internal recursive method for generating prefix indices.

pub fn get(&self, pfx: Pfx) -> Option<PfxTree>

Gets a child node by prefix character.

pub fn depth(&self) -> usize

Returns the depth of the tree.

pub fn unwrap_leaf(&self) -> usize

Unwraps a leaf node to get its response index.

Panics if called on a branch node.

pub fn regex_patterns(&self, keys: &[(String, usize)]) -> (String, String)

Generates regex patterns for matching response keys.

Returns (pattern with backticks, pattern without backticks).

Trait Implementations

impl Clone for PfxTree

fn clone(&self) -> PfxTree

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PfxTree

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

Formats the value using the given formatter.