JuliaDiff / JuliaDiff/ChainRules.jl

Chainrule for CUDA reduction

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good first issue missing rule
Dominant language
Julia
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Forks
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Description

Hi,

I'd like to suggest including a rule for GPU reductions.

using Zygote

function my_loss(v)
    # This works:
    # l = sum(v)
    # This does not work:
    l = reduce(+, v)
    return l
end

v = cu([1., 2.])
Zygote.gradient(my_loss, v)

See also: https://github.com/FluxML/Zygote.jl/issues/730#issuecomment-1221146525

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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 running the Julia reproduction in the issue with Zygote and the CUDA array, confirming that sum works while reduce(+, v) does not. Read the existing reduction rules in ChainRules.jl and compare their behavior with this case. Done means the supplied gradient call works for the GPU reduction and has coverage for the demonstrated example.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
machine-learning
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
32/100

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