Struct SumTree 

pub struct SumTree { /* private fields */ }

Binary sum-tree for O(log N) prefix-sum queries.

Internally stores 2 * capacity nodes where leaves occupy indices [capacity .. 2*capacity) and internal nodes hold partial sums.

Implementations

impl SumTree

pub fn new(capacity: usize) -> Self

Create a sum-tree with capacity leaves, all initialised to zero.

The capacity is rounded up to the next power of two for efficient binary-tree indexing. Unused leaves beyond the logical capacity hold priority 0.0 (sum-tree) and f64::INFINITY (min-tree). The min() method may therefore return INFINITY when the buffer is not full; callers should handle this (see PrioritizedReplayBuffer::tree_min_prob).

pub fn capacity(&self) -> usize

Number of leaves.

pub fn total(&self) -> f64

Sum of all leaf priorities.

pub fn min(&self) -> f64

Minimum leaf priority (O(1) via the min-tree).

pub fn set(&mut self, index: usize, priority: f64)

Set the priority of leaf index.

Panics (debug only)

Panics in debug builds if index >= capacity.

pub fn get(&self, index: usize) -> f64

Get the priority of leaf index.

Panics (debug only)

Panics in debug builds if index >= capacity.

pub fn sample(&self, value: f64) -> usize

Sample a leaf index such that the probability of choosing leaf i is priority[i] / total().

value should be in [0, total()).

Trait Implementations

impl Debug for SumTree

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

Formats the value using the given formatter.