#### Node clustering

- Merge nodes to form polytrees
- Merge CPTs

#### Catch

- Size of merged node values = size of merged CPT grows exponential to (NO. VALUES)^(MERGED NODES)
- Polytree algorithm is linear in CPT size
- Choosing optimal (efficient inference) clustering (make polytree) scheme is hard to answer

#### Cutset conditioning

- Instantiate node so that remaining nodes form a polytree
- Apply polytree algorithm separately on each subtree

#### Catch

- Cutset: set of instantiated nodes
- Number of sub-polytrees grows exponentially with the size of cutset
- Choosing optimal cutset is also hard to answer