/**
* Constructs a junction tree from a given factor graph. Does not perform BP in the resulting
* graph. So this gives you the structure of a jnuction tree, but the factors don't correspond to
* the true marginals unless you call BP yourself.
*
* @param mdl Factor graph to compute JT for.
*/
public JunctionTree buildJunctionTree(FactorGraph mdl) {
jtCurrent = (JunctionTree) mdl.getInferenceCache(JunctionTreeInferencer.class);
if (jtCurrent != null) {
jtCurrent.clearCPFs();
} else {
/* The graph g is the topology of the MRF that corresponds to the factor graph mdl.
* Essentially, this means that we triangulate factor graphs by converting to an MRF first.
* I could have chosen to trianglualte the FactorGraph directly, but I didn't for historical reasons
* (I already had a version of triangulate() for MRFs, not bipartite factor graphs.)
* Note that the call to mdlToGraph() is perfectly valid for FactorGraphs that are also DirectedModels,
* and has the effect of moralizing in that case. */
UndirectedGraph g = Graphs.mdlToGraph(mdl);
triangulate(g);
jtCurrent = buildJtStructure();
mdl.setInferenceCache(JunctionTreeInferencer.class, jtCurrent);
}
initJtCpts(mdl, jtCurrent);
return jtCurrent;
}
