solving PF memory growth issue

[lileicc]

disable the use of CBN in DefaultPossibleWorld, which is used in PF and LWSampler. But LWSampler doesnot need CBN information.

@jxwuyi @datang1992

[datang1992]

@lileicc Why do you want to remove this line? (About varToLogProb)

[lileicc]

since I already put it in setValue(...)
when value is null, I already put varToLogProb.remove(var).

[datang1992]

@lileicc LGTM with minor changes. But it will have several conflicts with the file changes in the branch #305 on the CBN part the partial world part.

[lileicc]

@datang1992
Note that the changes will only affect those using DefaultPossibleWorld, won't affect the PartialWorldDiff.
Therefore, only LWSampler and ParticleFilter will be affected.

[datang1992]

@lileicc
What I mean is that I changed something in the partial world file in the #305. Therefore there should be some conflicts.

[lileicc]

@datang1992 @jxwuyi
ready to review again.
Previously the PF might still accumulate memory, due the the variables in dirtyVars in AbstractPartialWorld will be accumulated if there is not evidence.

[lileicc]

@datang1992
As long as the underlying CBN is dynamical Bayesian network, it should be fine.
For open universe models, I donot think we support PF anyway.

[datang1992]

OK. If we don't allow PF for OU models, then it LGTM.

[jxwuyi]

@datang1992 @lileicc Why record object is necessary in Gibbs and MH?

[lileicc]

The exact answer is complicated. It is one way to record the usage graph.

[jxwuyi]

Overall LGTM