Junction Tree Algorithm¶

Inference Control¶

Used in controlling exact inference.

class pybbn.pptc.inferencecontroller.InferenceController¶

Bases: pybbn.graph.jointree.JoinTreeListener

Inference controller.

static apply(bbn)¶

Sets up the specified BBN for probability propagation in tree clusters (PPTC).

Parameters: bbn – BBN graph.
Returns: Join tree.

static apply_from_serde(join_tree)¶

Applies propagation to join tree from a deserialzed join tree.

Parameters: join_tree – Join tree.
Returns: Join tree (the same one passed in).

evidence_retracted(join_tree)¶

Evidence is retracted.

Parameters: join_tree – Join tree.

evidence_updated(join_tree)¶

Evidence is updated.

Parameters: join_tree – Join tree.

static reapply(join_tree, cpts)¶

Reapply propagation to join tree with new CPTs. The join tree structure is kept but the BBN node CPTs are updated. A new instance/copy of the join tree will be returned.

Parameters

join_tree – Join tree.
cpts – Dictionary of new CPTs. Keys are id’s of nodes and values are new CPTs.

Returns

Join tree.

Potential Initialization¶

Used to initialize potentials.

class pybbn.pptc.potentialinitializer.PotentialInitializer¶

Bases: object

Potential initializer.

static init(bbn)¶

Initializes the BBN potentials.

Parameters: bbn – BBN graph.

static reinit(jt)¶

Reinitialize potentials of BBN nodes in join tree.

Parameters: jt – Join tree.
Returns: None.

Moralization¶

Moralization of a directed acyclic graph.

class pybbn.pptc.moralizer.Moralizer¶

Bases: object

Graph moralizer for a DAG.

static moralize(dag)¶

Moralizes a DAG.

Parameters: dag – DAG.
Returns: Moralized (undirected) graph.

Triangulation¶

Triangulates a moralized graph.

class pybbn.pptc.triangulator.NodeClique(node, neighbors, weight, edges)¶

Bases: object

Node clique.

__init__(node, neighbors, weight, edges)¶

Ctor.

Parameters

node – BBN node.
neighbors – BBN nodes (neighbors).
weight – Weight.
edges – Edges.

get_bbn_nodes()¶

Gets all the BBN nodes in this node clique.

Returns: Array of BBN nodes.

class pybbn.pptc.triangulator.Triangulator¶

Bases: object

Triangulator. Triangulates an undirected moralized graph and produces cliques in the process.

static duplicate(g)¶

Duplicates a undirected graph.

Parameters: g – Undirected graph.
Returns: Undirected graph.

static generate_cliques(m)¶

Generates a list of node cliques.

Parameters: m – Graph.
Returns: List of NodeCliques.

static get_edges_to_add(n, m)¶

Gets edges to add.

Parameters

n – BBN node.
m – Graph.

Returns

Array of edges.

static get_weight(n, m)¶

Gets the weight of a BBN node. The weight of a node is the product of the its weight with all its neighbors’ weight.

Parameters

n – BBN node.
m – Graph.

Returns

Weight.

static is_subset(cliques, clique)¶

Checks if the specified clique is a subset of the specified list of cliques.

Parameters

cliques – List of cliques.
clique – Clique.

Returns

A boolean indicating if the clique is a subset.

static select_node(m)¶

Selects a clique from the specified graph. Cliques are sorted by number of edges, weight, and id (asc).

Parameters: m – Graph.
Returns: Clique.

static triangulate(m)¶

Triangulates the specified moralized graph.

Parameters: m – Moralized undirected graph.
Returns: Array of cliques.

Transformation¶

Transforms the cliques found from triangulation into a junction tree.

class pybbn.pptc.transformer.Transformer¶

Bases: object

Transformer. Transforms a list of cliques into a join tree.

static get_sep_sets(cliques)¶

Gets all pair-wise separation-sets.

Parameters: cliques – Array of cliques.
Returns: Array of separation sets sorted descendingly by mass followed by cost (asc) and id (asc).

static transform(cliques)¶

Transforms the cliques into a join tree.

Parameters: cliques – List of cliques.
Returns: Join tree.

Initialization¶

Initializes a junction tree.

class pybbn.pptc.initializer.Initializer¶

Bases: object

Initializes the join tree.

static get_clique(node, join_tree)¶

Gets the parent clique associated with the specified BBN node.

Parameters

node – BBN node.
join_tree – Join tree.

Returns

Parent clique.

static initialize(join_tree)¶

Starts the initialization.

Parameters: join_tree – Join tree.
Returns: Join tree.

Propagation¶

Propagates evidences in a junction tree.

class pybbn.pptc.propagator.Propagator¶

Bases: object

Evidence propagator.

static collect_evidence(join_tree, start)¶

Collects evidence.

Parameters

join_tree – Join tree.
start – Start clique.

static distribute_evidence(join_tree, start)¶

Distributes evidence.

Parameters

join_tree – Join tree.
start – Start clique.

static propagate(join_tree)¶

Propagates evidence.

Parameters: join_tree – Join tree.
Returns: Join tree.

Evidence Distribution¶

Distributes evidences.

class pybbn.pptc.evidencedistributor.EvidenceDistributor(join_tree, start_clique)¶

Bases: object

Evidence distributor. Passes messages using breadth-first-search (BFS). Messages are passed from the start clique to the far remote cliques.

__init__(join_tree, start_clique)¶

Ctor.

Parameters

join_tree – Join tree.
start_clique – Start clique.

start()¶: Starts the evidence distribution.

Evidence Collection¶

Collects evidences.

class pybbn.pptc.evidencecollector.EvidenceCollector(join_tree, start_clique)¶

Bases: object

Evidence collector. Passes messages using depth-first-search (DFS). Messages are passed from the far remote cliques back to the start clique.

__init__(join_tree, start_clique)¶

Ctor.

Parameters

join_tree – Join tree.
start_clique – Start clique.

start()¶: Starts the evidence collection.