stan-dev / stan-dev/posterior

stop using r_eff in ps_tail_length

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#446 2 comments 1 reaction 0 assignees View on GitHub

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Dominant language
R
Stars
171
Forks
26
Avg merge
2d 18h
Merged PRs (30d)
3

Description

I'm now convinced it was a mistake to use r_eff is ps_tail_length. Most of the time the difference is negligible, but sometimes it leads to strange behavior. I propose we drop it. We may need to keep allowing r_eff to be passed, but it should not be used for ps_tail_length computation. r_eff can still be useful for MCSE elsewhere

Contributor guide

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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 locating the ps_tail_length entry point and trace how r_eff is used in its computation. Confirm that r_eff remains accepted and available for MCSE-related work, while ps_tail_length no longer depends on it; existing tests, if present, should cover both behaviors.

Written by the indexing model from the issue text.

Assessment

Tech stack
r
Domain
data
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
50/100

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