PC, step by step

PC removes edges by conditional-independence tests, orients colliders, then applies Meek’s rules. Each step below was recorded by Andrey’s PC as it ran: the pseudocode marks the current line, and the graph and its endpoint-mark matrix show the state. The 4-variable example, rain and a sprinkler wetting the grass, plays one test per step; the 40-variable graph plays one depth per step.