What is the Hakaru Workflow?

When you write a Hakaru program, you must follow the workflow of Bayesian inference. Bayesian inference is a method of statistical inference where Bayes’ theorem is used to update the probability of a statistical hypothesis as more information becomes available¹. Bayes theorem describes the probability of an event based on knowledge of event-related conditions².

In Hakaru, the workflow of Bayesian inference appears as modelling, transformation, and application stages³:

1. In the modelling stage, you must create a probabilistic model of the environment as a prior probability distribution. This model requires you to include the known information and identify what information is to be inferred. The Hakaru language contains distributions and tools which formalize the modelling stage.
2. In the transformation stage, the prior distribution created in the modelling stage is transformed into a conditional distribution. During this stage, a function is created which maps known knowledge to a distribution that models the information that you want to infer. To automate this stage, Hakaru includes program transformations for model conditioning.
3. In the application stage, the function generated in the transformation stage is applied to the known knowledge that you have provided to get the posterior distribution on what is to be inferred. At the end of this stage, you can use Hakaru to show the resulting distribution as both a stream of samples and as a term in the Hakaru language.