Struct TraceScoringHandler 

pub struct TraceScoringHandler {
    pub trace: Trace,
}

A genuine [fugue::Handler] that scores a fixed trace of choices.

This is the evolutionary counterpart of Fugue’s own [fugue::runtime::interpreters::ScoreGivenTrace]: it starts from an existing [Trace] (typically genome.to_trace()), never samples fresh values, and accumulates log-weights with the correct bookkeeping:

• on_sample_* looks the value up in the base trace and adds its dist.log_prob(value) to log_prior,
• on_observe_* adds dist.log_prob(value) to log_likelihood,
• on_factor adds logw to log_factors,
• finish returns the (mutated) trace, whose choices are preserved.

Running the model factor(logw) through this handler therefore produces a trace with total_log_weight() == logw whose choice map still equals the original genome — this is exactly how “fitness as likelihood” is injected into a genome’s probability mass.

Fields

trace: Trace

The working trace. Seed it with the genome’s choices to score them.

Implementations

impl TraceScoringHandler

pub fn new(base: Trace) -> Self

Create a scoring handler seeded with base’s choices.

The accumulators of base are reset to zero so that the resulting total_log_weight() reflects only the effects executed by the model.

Trait Implementations

impl Handler for TraceScoringHandler

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_observe_f64( &mut self, _: &Address, dist: &dyn Distribution<f64>, value: f64, )

Handle an f64 observation operation.

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

Handle a bool observation operation.

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

Handle a u64 observation operation.

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

Handle a usize 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.

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

Handle an i64 sampling operation (signed discrete distributions).

fn on_observe_i64( &mut self, addr: &Address, _dist: &dyn Distribution<i64>, _value: i64, )

Handle an i64 observation operation.