From b0059267171ddbb250ecb8d5ff1d252d9386b74b Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Wed, 9 Feb 2022 17:13:03 +0800
Subject: [PATCH 1/2] Fix `stride(A, i)` for 0-dim inputs

---
 base/abstractarray.jl    |  2 +-
 base/reinterpretarray.jl |  2 ++
 test/abstractarray.jl    | 13 +++++++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index 5c4188b0f1471..524b4daa53fc7 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -546,7 +546,7 @@ julia> stride(A,3)
 function stride(A::AbstractArray, k::Integer)
     st = strides(A)
     k ≤ ndims(A) && return st[k]
-    return sum(st .* size(A))
+    return ndims(A) == 0 ? 1 : sum(st .* size(A))
 end
 
 @inline size_to_strides(s, d, sz...) = (s, size_to_strides(s * d, sz...)...)
diff --git a/base/reinterpretarray.jl b/base/reinterpretarray.jl
index 08638d26249a6..02707f4b02780 100644
--- a/base/reinterpretarray.jl
+++ b/base/reinterpretarray.jl
@@ -149,6 +149,8 @@ StridedMatrix{T} = StridedArray{T,2}
 StridedVecOrMat{T} = Union{StridedVector{T}, StridedMatrix{T}}
 
 strides(a::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}) = size_to_strides(1, size(a)...)
+stride(A::Union{DenseArray,StridedReshapedArray,StridedReinterpretArray}, k::Integer) =
+    k ≤ ndims(A) ? strides(A)[k] : length(A)
 
 function strides(a::ReshapedReinterpretArray)
     ap = parent(a)
diff --git a/test/abstractarray.jl b/test/abstractarray.jl
index a33cf53698d1c..300728a4b5f33 100644
--- a/test/abstractarray.jl
+++ b/test/abstractarray.jl
@@ -1580,6 +1580,19 @@ end
     end
 end
 
+@testset "stride for 0 dims array #44087" begin
+    struct Fill44087 <: AbstractArray{Int,0}
+        a::Int
+    end
+    # `stride` shouldn't work if `strides` is not defined.
+    @test_throws MethodError stride(Fill44087(1), 1)
+    # It is intentionally to only check the return type. (The value is somehow arbitrary)
+    @test stride(fill(1), 1) isa Int
+    @test stride(reinterpret(Float64, fill(Int64(1))), 1) isa Int
+    @test stride(reinterpret(reshape, Float64, fill(Int64(1))), 1) isa Int
+    @test stride(Base.ReshapedArray(fill(1), (), ()), 1) isa Int
+end
+
 @testset "to_indices inference (issue #42001 #44059)" begin
     @test (@inferred to_indices([], ntuple(Returns(CartesianIndex(1)), 32))) == ntuple(Returns(1), 32)
     @test (@inferred to_indices([], ntuple(Returns(CartesianIndices(1:1)), 32))) == ntuple(Returns(Base.OneTo(1)), 32)

From eb6b43ab36659abc88945ec465c9814f7c56181c Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Sat, 12 Feb 2022 01:39:55 +0800
Subject: [PATCH 2/2] Replace `sum( .* )` with for loop.

---
 base/abstractarray.jl | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/base/abstractarray.jl b/base/abstractarray.jl
index 524b4daa53fc7..e42b5d8c204f7 100644
--- a/base/abstractarray.jl
+++ b/base/abstractarray.jl
@@ -546,7 +546,13 @@ julia> stride(A,3)
 function stride(A::AbstractArray, k::Integer)
     st = strides(A)
     k ≤ ndims(A) && return st[k]
-    return ndims(A) == 0 ? 1 : sum(st .* size(A))
+    ndims(A) == 0 && return 1
+    sz = size(A)
+    s = st[1] * sz[1]
+    for i in 2:ndims(A)
+        s += st[i] * sz[i]
+    end
+    return s
 end
 
 @inline size_to_strides(s, d, sz...) = (s, size_to_strides(s * d, sz...)...)