FluxML/Zygote.jl

Use ChainRules types

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#603 opened on Apr 20, 2020

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 (5 comments) (5 reactions) (0 assignees)Julia (1,568 stars) (220 forks)batch import
ChainRuleshelp wantedup for grabs

Description

This issue is about swapping Zygote over to use ChainRule's types by default. When #366 is merged rules coming out of ChainRules will use its types like Composite and AbstractZero, but thing created via Source Code Transform (SCT) will still use NamedTuple and nothing.

This is fine as they are mutually compatible because accum falls back to + and ChainRules overloads +.

The use of Base types in Zygote tends to cause issues as its hard to add methods for NamedTuple and nothing, due to type piracy. Especially things like defining linear operations on them (e.g. overloading things from LinearAlgebra), as well as defining addition +. Particular discussion on Composite ans structured differential types is in #462

Related to: #454 #419 #329

Contributor guide

Tech stack
None
Domain
machine learning
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Julia programmingAutomatic differentiation conceptsZygote.jl internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the current usage of NamedTuple and nothing in Zygote's source code transform (SCT). Review ChainRules types Composite and AbstractZero as defined in ChainRules.jl. Examine the related issues #366, #462, #454, #419, #329 for context and prior discussion. Implement the swap ensuring backward compatibility via accum fallback.