Struct ReplayHandler 

pub struct ReplayHandler<'r, R: RngCore> {
    pub rng: &'r mut R,
    pub base: Trace,
    pub trace: Trace,
}

Handler for replaying models with values from an existing trace.

ReplayHandler replays a model execution using stored trace values. When a sampling site is encountered: if the address exists in the base trace, use that value; if missing, sample fresh. Essential for MCMC where you replay most choices but sample new values at specific sites.

Example:

// Create base trace
let mut rng = StdRng::seed_from_u64(42);
let model_fn = || sample(addr!("x"), Normal::new(0.0, 1.0).unwrap());
let (original, base_trace) = runtime::handler::run(
    PriorHandler { rng: &mut rng, trace: Trace::default() },
    model_fn()
);

// Replay using base trace values
let (replayed, _) = runtime::handler::run(
    ReplayHandler {
        rng: &mut rng,
        base: base_trace,
        trace: Trace::default()
    },
    model_fn()
);

assert_eq!(original, replayed); // Same value replayed

Fields

rng: &'r mut R

Random number generator for sampling at addresses not in base trace.

base: Trace

Base trace containing values to replay.

trace: Trace

New trace to accumulate the replay execution.

Trait Implementations

impl<'r, R: RngCore> Handler for ReplayHandler<'r, R>

fn on_sample_f64(&mut self, addr: &Address, dist: &dyn Distribution<f64>) -> f64

Handle an f64 sampling operation (continuous distributions).

fn on_sample_bool( &mut self, addr: &Address, dist: &dyn Distribution<bool>, ) -> bool

Handle a bool sampling operation (Bernoulli).

fn on_sample_u64(&mut self, addr: &Address, dist: &dyn Distribution<u64>) -> u64

Handle a u64 sampling operation (Poisson, Binomial).

fn on_sample_usize( &mut self, addr: &Address, dist: &dyn Distribution<usize>, ) -> usize

Handle a usize sampling operation (Categorical).

fn on_sample_i64(&mut self, addr: &Address, dist: &dyn Distribution<i64>) -> i64

Handle an i64 sampling operation (signed discrete distributions).

fn on_observe_f64( &mut self, _addr: &Address, dist: &dyn Distribution<f64>, value: f64, )

Handle an f64 observation operation.

fn on_observe_bool( &mut self, _addr: &Address, dist: &dyn Distribution<bool>, value: bool, )

Handle a bool observation operation.

fn on_observe_u64( &mut self, _addr: &Address, dist: &dyn Distribution<u64>, value: u64, )

Handle a u64 observation operation.

fn on_observe_usize( &mut self, _addr: &Address, dist: &dyn Distribution<usize>, value: usize, )

Handle a usize observation operation.

fn on_observe_i64( &mut self, _addr: &Address, dist: &dyn Distribution<i64>, value: i64, )

Handle an i64 observation operation.

fn on_factor(&mut self, logw: f64)

Handle a factor operation.

fn finish(self) -> Trace

Finalize the handler and return the accumulated trace.