JuliaDiff / JuliaDiff/ReverseDiff.jl

Perturbation Confusion (Nested Differentiation Bug)

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bug priority
Dominant language
Julia
Stars
393
Forks
60
Avg merge
18h 24m
Merged PRs (30d)
8

Description

I already mention this in ReverseDiff's documentation, but I'm opening this issue to increase visibility and track progress.

ReverseDiff has the same perturbation confusion issue as ForwardDiff. My plan to solve this in ReverseDiff is the same as my plan to solve this in ForwardDiff; the tag will be added to the TrackedArray/TrackedReal types (and possibly the tape types, I'm not sure yet).

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 with the existing ReverseDiff documentation and the linked ForwardDiff issue and plan. Determine how perturbation tags should be represented on TrackedArray and TrackedReal, and whether tape types are also involved. Done means nested differentiation no longer has perturbation confusion and the documented behavior is updated.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
backend
Issue type
Bug
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
20/100

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