io.improbable.keanu.algorithms.mcmc.proposal.PriorProposalDistribution Maven / Gradle / Ivy

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package io.improbable.keanu.algorithms.mcmc.proposal;

import io.improbable.keanu.KeanuRandom;
import io.improbable.keanu.algorithms.Variable;
import io.improbable.keanu.vertices.Probabilistic;
import io.improbable.keanu.vertices.Vertex;

import java.util.Collections;
import java.util.List;
import java.util.Set;

public class PriorProposalDistribution implements ProposalDistribution {
    private final ProposalNotifier proposalNotifier;

    public PriorProposalDistribution() {
        this(Collections.emptyList());
    }

    public PriorProposalDistribution(List listeners) {
        this.proposalNotifier = new ProposalNotifier(listeners);
    }

    @Override
    public Proposal getProposal(Set variables, KeanuRandom random) {
        Proposal proposal = new Proposal();
        for (Variable variable : variables) {
            setFor(variable, random, proposal);
        }
        proposalNotifier.notifyProposalCreated(proposal);
        return proposal;
    }

    @Override
    public  double logProb(Probabilistic variable, T ofValue, T givenValue) {
        return variable.logProb(ofValue);
    }

    private  void setFor(Variable variable, KeanuRandom random, Proposal proposal) {

        if (variable instanceof Vertex && variable instanceof Probabilistic) {
            Vertex vertex = (Vertex) variable;
            proposal.setProposal(variable, ((Probabilistic) vertex).sample(random));
        } else {
            throw new IllegalArgumentException(this.getClass().getSimpleName() + " is to only be used with Keanu's Vertex");
        }
    }

    @Override
    public void onProposalRejected() {
        proposalNotifier.notifyProposalRejected();
    }

}