https://github.com/tkf/chaincutters.jl

https://github.com/tkf/chaincutters.jl

Last synced: 11 months ago
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• Host: GitHub
• URL: https://github.com/tkf/chaincutters.jl
• Owner: tkf
• License: mit
• Created: 2019-09-18T06:42:55.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2020-02-08T14:43:49.000Z (almost 6 years ago)
• Last Synced: 2024-12-31T09:25:02.879Z (about 1 year ago)
• Language: Julia
• Size: 41 KB
• Stars: 2
• Watchers: 3
• Forks: 1
• Open Issues: 2
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
# ChainCutters

[![Build Status](https://travis-ci.com/tkf/ChainCutters.jl.svg?branch=master)](https://travis-ci.com/tkf/ChainCutters.jl)

[![Codecov](https://codecov.io/gh/tkf/ChainCutters.jl/branch/master/graph/badge.svg)](https://codecov.io/gh/tkf/ChainCutters.jl)

[![Coveralls](https://coveralls.io/repos/github/tkf/ChainCutters.jl/badge.svg?branch=master)](https://coveralls.io/github/tkf/ChainCutters.jl?branch=master)

## Treating arguments as constants

Use `ChainCutters.cut(x)` to treat `x` as a constant.  Only `*`, `+`

and `-` are supported.

```julia

julia> using ChainCutters: cut

julia> using LinearAlgebra, Zygote

julia> A = [

           1  9  1

           9  1  2

           5  3  5

       ];

julia> B = [

           7  9  1

           9  1  6

           5  3  5

       ];

julia> C, back = Zygote.pullback(A, B) do A, B

           cut(A) * B

       end;

julia> C == A * B

true

julia> ∂A, ∂B = back(I(3));

julia> ∂A === nothing  # `A` is treated as a constant

true

julia> ∂B

3×3 Array{Int64,2}:

 1  9  5

 9  1  3

 1  2  5

```

## Treating specific fields of constant object as variables

Fields inside objects marked as constant by `cut` can be marked as a

variable using `uncut`.

```julia

julia> using ChainCutters: uncut

julia> using Setfield

julia> C, back = Zygote.pullback((A = A, B = B, alpha = 2)) do p

           q = cut(@set p.B = uncut(p.B))  # only treat `B` as varying

           q.A * q.B * q.alpha

       end;

julia> C == A * B * 2

true

julia> ∂p, = back(I(3));

julia> ∂p

(A = nothing, B = [2 18 10; 18 2 6; 2 4 10], alpha = nothing)

```