Struct PerfSnapshot 

pub struct PerfSnapshot {
    pub elapsed: Option<Duration>,
    pub counters: [u64; 56],
    pub thunks_created: u64,
    pub thunks_forced: u64,
}

An immutable snapshot of counter + timer state at a single point.

Cheap to clone (just a fixed-size array + a few u64). Subtract two snapshots (b.delta_from(&a)) to get the work done between them — the foundation of with_scope and per-program profiling.

Fields

elapsed: Option<Duration>

Wall-clock elapsed since start was called. None if start wasn’t called in this thread.

counters: [u64; 56]

Raw counter values, indexed by Counter as usize.

thunks_created: u64

Thunks allocated in this thread to date (from trace module).

thunks_forced: u64

Thunks forced (from suspended → evaluated) to date.

Implementations

impl PerfSnapshot

pub fn zero() -> Self

All-zero snapshot. Useful as the identity element for folds.

pub fn get(&self, counter: Counter) -> u64

Read a counter by enum variant.

pub fn delta_from(&self, other: &PerfSnapshot) -> PerfSnapshot

self - other, treating both as counter totals. Used to get the delta across a scoped evaluation (snapshot before, snapshot after, subtract). Saturates to zero on underflow — shouldn’t happen in normal use but guards against races / manual resets.

pub fn thunk_hit_rate(&self) -> Option<f64>

Thunk memoization hit rate — 1.0 means every suspended thunk produced useful work; 0.0 means everything we built was wasted. Returns None when no thunks were created in this window.

pub fn dominant_expr_kind(&self) -> Option<(Counter, u64)>

(top_variant, count) — the expression kind with the highest count in this snapshot. For ranking “what is this eval mostly doing?” at a glance.

Trait Implementations

impl Clone for PerfSnapshot

fn clone(&self) -> PerfSnapshot

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for PerfSnapshot

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

Formats the value using the given formatter.