Registers the built-in cmdstanr executor node kinds: stan_data,
cmdstanr_fit, prior_fit, loo, compare, ppc, loo_pit, and sbc.
Each executor is a built-in resolved by reference (no source text
persisted). The fit executors compute HMC diagnostics themselves and emit
hmc_diagnostics
summaries with severity rules; no user-written diagnostic code is required.
Details
Each execution records provenance in its job record (see bg_node_pad()).
The fit kinds report the data input they consumed and the sampler settings
read back from the fitted object, and declare a P/A/D classification of
their parameters (see the pad argument of bg_register_node_kind()).
The loo, ppc, and loo_pit kinds report the fit input they evaluated.
The ppc kind's posterior-predictive p-values are conservative checks:
an extreme value flags substantial misfit, but an unremarkable value is weak
evidence that the model is adequate. Treat the graphical check via
bg_plot() as the primary posterior-predictive diagnostic and the
p-values as supplementary checks.