pymc-devs / pymc-devs/pymc

Question/Feature request: Figuring out how often the model/gradient was evaluated by NUTS

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feature request question
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Python
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Description

This question came up during office hours:

Which sampler stat should be used to answer how often a model was evaluated during MCMC?

@junpenglao @ColCarroll

For example, these variables are tracked by NUTS:

  • process_time_diff
  • lp
  • max_energy_error
  • perf_counter_diff
  • diverging
  • acceptance_rate
  • step_size
  • energy_error
  • perf_counter_start
  • n_steps
  • tree_depth
  • step_size_bar
  • energy

If we're not currently tracking the information of how often the model was evaluated, we should definitely add that stat!

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by inspecting the NUTS sampler-stat collection and the listed statistics, especially n_steps and tree_depth, to determine whether any already represent model evaluations. If the count is not tracked, define the statistic's meaning and expose it alongside the existing NUTS stats; done means users can identify how often the model was evaluated during MCMC.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
machine-learning
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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