modppl 0.3.1

a experimental library for probabilistic programming in Rust.
Documentation 
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use crate::Real;
use crate::{ArgDiff, DynGenFn, DynGenFnHandler, DynTrie, GenFn, ParticleSystem, Trace};
use rand::rngs::ThreadRng;

/// Combinator struct for kernels that use the `DynGenFnHandler` DSL (`sample_at` and `trace_at`).
/// Supports memory-efficient extension via the `GfDiff::Extend` flag (eg. as passed during a `ParticleSystem::step`).
pub struct DynUnfold<State> {
    /// A stochastic kernel that takes in a mutable reference to a `DynGenFnHandler<A,T>` and some `State`, effectfully mutates it, and produces a new `State`.
    pub kernel: DynGenFn<(i64, State), State>,
}

impl<State> DynUnfold<State> {
    /// Dynamically construct a `DynUnfold` from a kernel function at run-time.
    pub fn new(kernel: DynGenFn<(i64, State), State>) -> Self {
        DynUnfold { kernel }
    }
}

///
pub type DynParticles<State> = ParticleSystem<State, Vec<DynTrie>, Vec<State>, DynUnfold<State>>;

impl<State: Clone> GenFn<(i64, State), Vec<DynTrie>, Vec<State>> for DynUnfold<State> {
    fn simulate(
        &self,
        final_t_and_args: (i64, State),
    ) -> Trace<(i64, State), Vec<DynTrie>, Vec<State>> {
        let (final_t, mut state) = final_t_and_args;
        assert!(final_t >= 1);
        let mut vec_trace = Trace {
            args: (final_t, state.clone()),
            data: vec![],
            retv: Some(vec![]),
            logjp: 0.,
        };
        for t in 0..final_t {
            let mut g = DynGenFnHandler::Simulate {
                prng: &mut ThreadRng::default(),
                trace: Trace {
                    args: (t as i64, state.clone()),
                    data: DynTrie::new(),
                    retv: None,
                    logjp: 0.,
                },
            };
            state = (self.kernel.func)(&mut g, (t as i64, state.clone()));
            let DynGenFnHandler::Simulate { prng: _, trace } = g else {
                unreachable!()
            };
            vec_trace.retv.as_mut().unwrap().push(state.clone());
            vec_trace.data.push(trace.data);
            vec_trace.logjp += trace.logjp;
        }
        vec_trace
    }

    fn generate(
        &self,
        final_t_and_args: (i64, State),
        vec_constraints: Vec<DynTrie>,
    ) -> (Trace<(i64, State), Vec<DynTrie>, Vec<State>>, Real) {
        let (final_t, mut state) = final_t_and_args;
        assert!(final_t >= 1);
        let mut vec_trace = Trace {
            args: (final_t, state.clone()),
            data: vec![],
            retv: Some(vec![]),
            logjp: 0.,
        };
        let mut gen_weight = 0.;
        for (t, constraints) in vec_constraints.into_iter().enumerate() {
            let mut g = DynGenFnHandler::Generate {
                prng: &mut ThreadRng::default(),
                trace: Trace {
                    args: (t as i64, state.clone()),
                    data: DynTrie::new(),
                    retv: None,
                    logjp: 0.,
                },
                weight: 0.,
                constraints,
            };
            state = (self.kernel.func)(&mut g, (t as i64, state.clone()));
            let DynGenFnHandler::Generate {
                prng: _,
                trace,
                weight,
                constraints,
            } = g
            else {
                unreachable!()
            };
            assert!(constraints.is_empty());
            vec_trace.retv.as_mut().unwrap().push(state.clone());
            vec_trace.data.push(trace.data);
            vec_trace.logjp += trace.logjp;
            gen_weight += weight;
        }
        (vec_trace, gen_weight)
    }

    fn update(
        &self,
        mut vec_trace: Trace<(i64, State), Vec<DynTrie>, Vec<State>>,
        final_t_and_args: (i64, State),
        diff: ArgDiff,
        vec_constraints: Vec<DynTrie>,
    ) -> (
        Trace<(i64, State), Vec<DynTrie>, Vec<State>>,
        Vec<DynTrie>,
        Real,
    ) {
        let (final_t, _) = final_t_and_args;
        assert!(final_t >= 1);
        let prev_t = vec_trace.args.0;
        assert!(final_t - prev_t == vec_constraints.len() as i64);
        let mut state = vec_trace.retv.as_ref().unwrap().last().unwrap().clone();
        let mut update_weight = 0.;
        match diff {
            ArgDiff::Extend => {
                for (t, constraints) in vec_constraints.into_iter().enumerate() {
                    let mut g = DynGenFnHandler::Generate {
                        prng: &mut ThreadRng::default(),
                        trace: Trace {
                            args: (prev_t + (t as i64), state.clone()),
                            data: DynTrie::new(),
                            retv: None,
                            logjp: 0.,
                        },
                        weight: 0.,
                        constraints,
                    };
                    state = (self.kernel.func)(&mut g, (prev_t + (t as i64), state.clone()));
                    let DynGenFnHandler::Generate {
                        prng: _,
                        trace,
                        weight,
                        constraints,
                    } = g
                    else {
                        unreachable!()
                    };
                    assert!(constraints.is_empty());
                    vec_trace.args.0 += 1;
                    vec_trace.retv.as_mut().unwrap().push(state.clone());
                    vec_trace.data.push(trace.data);
                    vec_trace.logjp += trace.logjp;
                    update_weight += weight;
                }
            }
            _ => {
                panic!("Can't handle GF change type: {:?}", diff)
            }
        }
        (
            vec_trace,
            (prev_t..final_t).map(|_| DynTrie::new()).collect::<_>(),
            update_weight,
        )
    }
}