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Variational inference

There are two procedures in the inference library for performing black box variational inference. Each of these procedures can also train the model using stochastic gradient descent, as in a variational autoencoder.

Gen.black_box_vi! — Function
(elbo_estimate, traces, elbo_history) = black_box_vi!(
    model::GenerativeFunction, model_args::Tuple,
    [model_update::ParamUpdate,]
    observations::ChoiceMap,
    var_model::GenerativeFunction, var_model_args::Tuple,
    var_model_update::ParamUpdate;
    options...)

Fit the parameters of a variational model (var_model) to the posterior distribution implied by the given model and observations using stochastic gradient methods. Users may optionally specify a model_update to jointly update the parameters of model.

Additional arguments:

  • iters=1000: Number of iterations of gradient descent.
  • samples_per_iter=100: Number of samples from the variational and generative model to accumulate gradients over before a single gradient step.
  • verbose=false: If true, print information about the progress of fitting.
  • callback: Callback function that takes (iter, traces, elbo_estimate) as input, where iter is the iteration number and traces are samples from var_model for that iteration.
source
Gen.black_box_vimco! — Function
(iwelbo_estimate, traces, iwelbo_history) = black_box_vimco!(
    model::GenerativeFunction, model_args::Tuple,
    [model_update::ParamUpdate,]
    observations::ChoiceMap,
    var_model::GenerativeFunction, var_model_args::Tuple,
    var_model_update::ParamUpdate,
    grad_est_samples::Int; options...)

Fit the parameters of a variational model (var_model) to the posterior distribution implied by the given model and observations using stochastic gradient methods applied to the Variational Inference with Monte Carlo Objectives (VIMCO) lower bound on the marginal likelihood. Users may optionally specify a model_update to jointly update the parameters of model.

Additional arguments:

  • grad_est_samples::Int: Number of samples for the VIMCO gradient estimate.
  • iters=1000: Number of iterations of gradient descent.
  • samples_per_iter=100: Number of samples from the variational and generative model to accumulate gradients over before a single gradient step.
  • geometric=true: Whether to use the geometric or arithmetric baselines described in Variational Inference with Monte Carlo Objectives
  • verbose=false: If true, print information about the progress of fitting.
  • callback: Callback function that takes (iter, traces, elbo_estimate) as input, where iter is the iteration number and traces are samples from var_model for that iteration.
source