Delete special case for sum(f, ::Adjoint) (#618)

* fix 530

* bump version

Author: mcabbott

Project.toml

@@ -1,6 +1,6 @@
 name = "ChainRules"
 uuid = "082447d4-558c-5d27-93f4-14fc19e9eca2"
-version = "1.31.0"
+version = "1.32.0"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"

src/rulesets/Base/mapreduce.jl

@@ -51,26 +51,6 @@ end
 ##### `sum(f, x)`
 #####
 
-# Can't map over Adjoint/Transpose Vector
-function rrule(
-    config::RuleConfig{>:HasReverseMode},
-    ::typeof(sum),
-    f,
-    xs::Union{Adjoint{<:Number,<:AbstractVector},Transpose{<:Number,<:AbstractVector}};
-    kwargs...
-)
-    op = xs isa Adjoint ? adjoint : transpose
-    # since summing a vector we don't need to worry about dims which simplifies adjointing
-    vector = parent(xs)
-    y, vector_sum_pb = rrule(config, sum, f, vector; kwargs...)
-    function covector_sum_pb(ȳ)
-        s̄um, f̄, v̄ = vector_sum_pb(ȳ)
-        return s̄um, f̄, op(v̄)
-    end
-
-    return y, covector_sum_pb
-end
-
 function rrule(
     config::RuleConfig{>:HasReverseMode},
     ::typeof(sum),
@@ -96,7 +76,8 @@ function rrule(
     # see `f.(xs)` but we don't need the pullbacks. Not implemented at present.)
 
     # In the general case, we need to save all the pullbacks:
-    fx_and_pullbacks = map(xᵢ -> rrule_via_ad(config, f, xᵢ), xs)
+    # (Here `map` or `broadcast` would fail for adjoint vectors.)
+    fx_and_pullbacks = [rrule_via_ad(config, f, xᵢ) for xᵢ in xs]
     y = sum(first, fx_and_pullbacks; dims)
 
     function sum_pullback_f2(dy)

test/rulesets/Base/mapreduce.jl

@@ -95,6 +95,10 @@ const CFG = ChainRulesTestUtils.ADviaRuleConfig()
         test_rrule(sum, inv, x[1, :]')
         test_rrule(sum, inv, x[1:1, :]')
         test_rrule(sum, inv, transpose(view(x, 1, :)))
+        # Cases from https://github.com/JuliaDiff/ChainRules.jl/issues/530
+        test_rrule(sum, log, [1, 2, 3.0]'; fkwargs=(;dims=1))
+        test_rrule(sum, log, [1, 2, 3.0]'; fkwargs=(;dims=2))
+        test_rrule(sum, imag, [1+2im, 3+4.0im]')
 
         # Make sure we preserve type for StaticArrays
         _, pb = rrule(CFG, sum, abs, @SVector[1.0, -3.0])