blog
Class DecayedProposer

java.lang.Object
  blog.GenericProposer
      blog.DecayedProposer

All Implemented Interfaces:

Proposer

public class DecayedProposer
extends GenericProposer

A DecayedProposer as defined by Bhaskara Marthi, Hanna Pasula, Stuart Russell, Yuval Peres, "Decayed MCMC Filtering" (2002). It follows the method used by GenericProposer, but differs in how it chooses the variable to be sampled. Whereas GenericProposer chooses a variable uniformly from the instantiated ones, DecayedProposer first decides whether it will choose a temporal or an atemporal variable. If it decides for an atemporal variable, then it chooses uniformly among them. If it decides for a temporal variable, then it first chooses a timestep from which to sample, with probability inverse-polynomially proportional to the distance between this timestep and the current timestep. Then it samples uniformly from the temporal variables with that timestep. The probability of choosing to pick an atemporal variable is atemporalVarFactor/(atemporalVarFactor + current timestep), where atemporalVarFactor is provided in the Properties passed to the constructor.

The DecayedProposer also accepts a property maxRecall, with default 30, that limits how many timesteps it looks back.

Nested Class Summary

Nested classes/interfaces inherited from class blog.GenericProposer

GenericProposer.PickVarToSampleResult

Field Summary

protected static int

maxRecall

Fields inherited from class blog.GenericProposer

evidence, evidenceVars, initialStateSampler, logProbBackward, logProbForward, model, numBasicEvidenceVars, numInitialStateTriesThisTrial, numTrials, queries, queryVars, totalNumInitialStateTries

Constructor Summary

DecayedProposer(Model model, java.util.Properties properties)
Constructs a DecayedProposer based on the given model and properties.

Method Summary

int	getMaxRecall()
protected GenericProposer.PickVarToSampleResult	pickVarToSample(PartialWorldDiff world)

Methods inherited from class blog.GenericProposer

add, addQueries, constructInitialState, initialize, pickVarToSample, printStats, proposeNextState, updateStats

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

maxRecall

protected static int maxRecall

Constructor Detail

DecayedProposer

public DecayedProposer(Model model,
                       java.util.Properties properties)

Constructs a DecayedProposer based on the given model and properties. Besides those properties used by the super class GenericProposer, DecayedProposer used the properties maxRecall, an integer determining how many timesteps back the proposer uses at most (default 30), and atemporalVarFactor, a double indicating the weight of atemporal variables, relative to each timestep, in the choice of a variable to be sampled (with default 1.0).

Method Detail

pickVarToSample

protected GenericProposer.PickVarToSampleResult pickVarToSample(PartialWorldDiff world)

getMaxRecall

public int getMaxRecall()