Issue 313 (#475)

* WIP

* add chainrules frule, rrule

* correct merge

Author: jverzani

Project.toml

@@ -5,16 +5,19 @@ author = "JuliaMath"
 version = "3.2.5"
 
 [deps]
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 MakieCore = "20f20a25-4f0e-4fdf-b5d1-57303727442b"
 RecipesBase = "3cdcf5f2-1ef4-517c-9805-6587b60abb01"
 
 [compat]
-RecipesBase = "0.7, 0.8, 1"
+ChainRulesCore = "1"
 MakieCore = "0.6"
+RecipesBase = "0.7, 0.8, 1"
 julia = "1.6"
 
 [extras]
+ChainRulesTestUtils = "cdddcdb0-9152-4a09-a978-84456f9df70a"
 DualNumbers = "fa6b7ba4-c1ee-5f82-b5fc-ecf0adba8f74"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"

src/Polynomials.jl

@@ -35,7 +35,7 @@ include("rational-functions/plot-recipes.jl")
 
 # compat; opt-in with `using Polynomials.PolyCompat`
 include("polynomials/Poly.jl")
-
+include("chain_rules.jl")
 include("precompiles.jl")
 
 end # module

src/chain_rules.jl

@@ -0,0 +1,16 @@
+import ChainRulesCore
+
+function ChainRulesCore.frule(
+    config::ChainRulesCore.RuleConfig{>:ChainRulesCore.HasForwardsMode},
+    (_, Δx),
+    p::AbstractPolynomial,
+    x
+)
+    p(x), derivative(p)(x)*Δx
+end
+
+
+function ChainRulesCore.rrule(p::AbstractPolynomial, x)
+    _pullback(ΔΩ) = (ChainRulesCore.NoTangent(), derivative(p)(x))
+    return (p(x), _pullback)
+end

test/Project.toml

@@ -1,4 +1,5 @@
 [deps]
+ChainRulesTestUtils = "cdddcdb0-9152-4a09-a978-84456f9df70a"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 MutableArithmetics = "d8a4904e-b15c-11e9-3269-09a3773c0cb0"
 OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"

test/StandardBasis.jl

@@ -1603,3 +1603,14 @@ end
     @test Polynomials.minimumexponent(LaurentPolynomial{Float64}) == typemin(Int)
     @test Polynomials.minimumexponent(LaurentPolynomial{Float64, :y}) == typemin(Int)
 end
+
+
+# Chain rules
+using ChainRulesTestUtils
+
+@testset "Test frule and rrule" begin
+    p = Polynomial([1,2,3,4])
+    dp = derivative(p)
+
+    test_scalar(p, 1.0; check_inferred=true)
+end