Struct TransitionMatrix 

pub struct TransitionMatrix {
    pub row_pointers: Vec<u32>,
    pub data: Vec<[u32; 2]>,
    pub max_branches: Vec<u32>,
    pub num_nodes: u32,
    pub vocab_size: u32,
    pub sid_length: u32,
}

Stacked CSR transition matrix: interleaves [col_idx, next_state] for coalesced reads. Row i corresponds to trie node i; values are (token_id, next_node_id) pairs.

Fields

row_pointers: Vec<u32>

CSR row pointers: length = num_nodes + 1. row_pointers[i]..row_pointers[i+1] is the slice in data for node i.

data: Vec<[u32; 2]>

Interleaved pairs: [(token_id, next_node_id), …]

max_branches: Vec<u32>

Max observed branch factor at each trie depth: length = sid_length.

num_nodes: u32

Total number of trie nodes (states).

vocab_size: u32

Vocabulary size |V|.

sid_length: u32

Semantic ID length L.

Implementations

impl TransitionMatrix

pub fn new(num_nodes: u32, vocab_size: u32, sid_length: u32) -> Self

Construct an empty matrix for num_nodes nodes.

pub fn children(&self, node: u32) -> &[[u32; 2]]

Returns the children slice for node as &[[token_id, next_node]; _].

Panics

Panics if node >= num_nodes.

pub fn next_node(&self, node: u32, token: u32) -> Option<u32>

Looks up the next node reached from node by emitting token. Returns None if the transition does not exist (invalid / masked).

pub fn is_leaf(&self, node: u32) -> bool

Returns true if node has no outgoing transitions (i.e. is a leaf).

pub fn degree(&self, node: u32) -> u32

Number of outgoing transitions (branches) from node.

pub fn check_invariants(&self) -> Result<(), String>

Validates internal invariants; useful inside debug_assert!.

impl TransitionMatrix

pub fn vntk(&self, current_nodes: &[u32], level: usize) -> VntkResult

Vectorized Node Transition Kernel — Algorithm 2 from the paper.

For each of the n = batch_size × beam_width active beams, reads the CSR row for that beam’s current trie node and writes up to B_t (token, next-node) pairs into pre-allocated output buffers.

Layout

All output buffers are flat and strided by branch_size (= B_t).

Parallelism

The per-beam inner loop is embarrassingly parallel and runs via Rayon. Writes to disjoint buffer slices avoid any synchronisation overhead.

Arguments

• current_nodes — flat slice of length n, one node ID per beam
• level — current decoding step (0-indexed); selects B_t

Panics

Panics if level >= sid_length or any node ID ≥ num_nodes.

pub fn vntk_single(&self, node: u32, level: usize) -> VntkOutput

Thin wrapper that converts a VntkResult into the simpler VntkOutput expected by the test module (next_nodes flat vec + single bool mask).

Only meaningful when current_nodes contains a single beam; for multi-beam callers use VntkResult directly.

Trait Implementations

impl Clone for TransitionMatrix

fn clone(&self) -> TransitionMatrix

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for TransitionMatrix

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

Formats the value using the given formatter.

impl Display for TransitionMatrix

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

Formats the value using the given formatter.

impl PartialEq for TransitionMatrix

fn eq(&self, other: &TransitionMatrix) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for TransitionMatrix

impl StructuralPartialEq for TransitionMatrix