From 5a0fa7e308a5a8c9ccf1390eb8c0c9095c32cf0f Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Mon, 10 Jan 2022 17:39:33 +0800
Subject: [PATCH 1/2] Make `has_fast_linear_indexing` based on `IndexStyle` and
 `ndims`

---
 base/reducedim.jl | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/base/reducedim.jl b/base/reducedim.jl
index 1d74fb0d498a5..4ab786804ff4c 100644
--- a/base/reducedim.jl
+++ b/base/reducedim.jl
@@ -196,11 +196,8 @@ end
 
 ## generic (map)reduction
 
-has_fast_linear_indexing(a::AbstractArrayOrBroadcasted) = false
-has_fast_linear_indexing(a::Array) = true
-has_fast_linear_indexing(::Union{Number,Ref,AbstractChar}) = true  # 0d objects, for Broadcasted
-has_fast_linear_indexing(bc::Broadcast.Broadcasted) =
-    all(has_fast_linear_indexing, bc.args)
+has_fast_linear_indexing(a::AbstractArrayOrBroadcasted) = IndexStyle(a) === IndexLinear()
+has_fast_linear_indexing(a::AbstractVector) = true
 
 function check_reducedims(R, A)
     # Check whether R has compatible dimensions w.r.t. A for reduction

From a23a31855f9d61fed59d4578489ea256f3944278 Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Mon, 10 Jan 2022 17:46:33 +0800
Subject: [PATCH 2/2] add test

---
 test/broadcast.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/broadcast.jl b/test/broadcast.jl
index e4309bf81419f..b2232258744ac 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -979,6 +979,10 @@ end
     @test sum(bc, dims=1, init=0) == [5]
     bc = Broadcast.instantiate(Broadcast.broadcasted(*, ['a','b'], 'c'))
     @test prod(bc, dims=1, init="") == ["acbc"]
+
+    a = rand(-10:10,32,4); b = rand(-10:10,32,4)
+    bc = Broadcast.instantiate(Broadcast.broadcasted(+,a,b))
+    @test sum(bc; dims = 1, init = 0.0) == sum(collect(bc); dims = 1, init = 0.0)
 end
 
 # treat Pair as scalar: