Struct ArithmeticGrammarPrior 

pub struct ArithmeticGrammarPrior {
    pub terminal_prob: f64,
    pub max_depth: usize,
    pub n_vars: usize,
    pub p_var: f64,
    pub const_std: f64,
    pub n_functions: usize,
}

A probabilistic context-free grammar prior over arithmetic expression trees.

Fields

terminal_prob: f64

Probability that a node (below max depth) is a terminal.

max_depth: usize

Maximum tree depth; nodes at this depth are forced terminal.

n_vars: usize

Number of input variables x0..x{n_vars-1}.

p_var: f64

Probability that a terminal is a variable (vs a constant).

const_std: f64

Standard deviation of the Gaussian prior over constants.

n_functions: usize

Restrict the function set to the first n_functions entries of ArithmeticFunction::functions (e.g. 4 = {Add, Sub, Mul, Div}).

Trait Implementations

impl Clone for ArithmeticGrammarPrior

fn clone(&self) -> ArithmeticGrammarPrior

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for ArithmeticGrammarPrior

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

Formats the value using the given formatter.

impl Default for ArithmeticGrammarPrior

fn default() -> Self

Returns the “default value” for a type.

impl GenomePrior for ArithmeticGrammarPrior

fn trace_of(&self, genome: &Self::Genome) -> Trace

Encode a tree under the grammar’s own address scheme (the inverse of running Self::model): a deterministic walk emitting the #leaf/#tkind/#var/#const/#func choices at each node path.

This is what makes EvolutionModel::score, to_weighted_trace, and EvolutionChain::init_from work for grammar-driven trees: replaying the encoding through the grammar program recovers the genuine PCFG log-prior. A tree using a function outside the restricted n_functions set, or deeper than max_depth, scores −∞ under replay (out of the prior’s support) rather than erroring.

Erc terminals are encoded as constants (evaluation-identical; the grammar itself only generates Variable/Constant).

type Genome = TreeGenome

The genome type this prior generates.

fn model(&self) -> Model<Self::Genome>

The generative program p(x).