bdsprior

confirmedupstream bugPython · pgmpySystems & data structuresJuly 25, 2026

the question

Does pgmpy's BDs structure score compute a valid Dirichlet marginal likelihood under unobserved parent configurations?

what came out

pgmpy's BDs sets the configuration concentration to ess/qtilde but cell concentrations summing to ess/q, violating alpha=r*beta, and adds the configuration prior for only the qtilde observed configs. On sparse data the score is off by 13.3 nats; the sibling BDeu is exact.

method & receipts

Result: confirmed
Reproducible — one script re-runs the whole thing from scratch.
Tested — a correctness/benchmark suite ships alongside the code.

→ read the code and re-run it

github.com/v-code01/bdsprior