Merge d9461cd into f63f385

JuliaDiff · Oct 15, 2020 · 3f50382 · 3f50382
2 parents f63f385 + d9461cd
commit 3f50382
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diff --git a/src/rulesets/Base/arraymath.jl b/src/rulesets/Base/arraymath.jl
@@ -104,3 +104,14 @@ function rrule(::typeof(\), b::Real, A::AbstractArray{<:Real})
     end
     return Y, backslash_pullback
 end
+
+#####
+##### Negation (Unary -)
+#####
+
+function rrule(::typeof(-), x::AbstractArray)
+    function negation_pullback(ȳ)
+        return NO_FIELDS, InplaceableThunk(@thunk(-ȳ), ā -> ā .-= ȳ)
+    end
+    return -x, negation_pullback
+end
diff --git a/test/rulesets/Base/arraymath.jl b/test/rulesets/Base/arraymath.jl
@@ -63,4 +63,13 @@
         rrule_test(/, Ȳ, (A, Ā), (7.2, 2.3))
         rrule_test(\, Ȳ, (7.2, 2.3), (A, Ā))
     end
+
+
+    @testset "negation" begin
+        A = randn(4, 4)
+        Ā = randn(4, 4)
+        Ȳ = randn(4, 4)
+        rrule_test(-, Ȳ, (A, Ā))
+        rrule_test(-, Diagonal(Ȳ), (Diagonal(A), Diagonal(Ā)))
+    end
 end