Fix indexing in _mapreducedim for OffsetArrays

JuliaLang · Aug 16, 2024 · bf66e74 · bf66e74
1 parent 5230d27
commit bf66e74
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Showing 2 changed files with 11 additions and 2 deletions.
diff --git a/base/reducedim.jl b/base/reducedim.jl
@@ -258,8 +258,10 @@ function _mapreducedim!(f, op, R::AbstractArray, A::AbstractArrayOrBroadcasted)
         # use mapreduce_impl, which is probably better tuned to achieve higher performance
         nslices = div(length(A), lsiz)
         ibase = first(LinearIndices(A))-1
-        for i = 1:nslices
-            @inbounds R[i] = op(R[i], mapreduce_impl(f, op, A, ibase+1, ibase+lsiz))
+        for i = range(firstindex(R), length=nslices)
+            v = mapreduce_impl(f, op, A, ibase+1, ibase+lsiz)
+            r = op(@inbounds(R[i]), v)
+            @inbounds R[i] = r
             ibase += lsiz
         end
         return R

diff --git a/test/offsetarray.jl b/test/offsetarray.jl
@@ -907,3 +907,10 @@ end
     v = view([1,2,3,4], :)
     @test v[Base.IdentityUnitRange(2:3)] == OffsetArray(2:3, 2:3)
 end
+
+@testset "mapreduce with OffsetRanges" begin
+    r = 5:100
+    a = OffsetArray(r, 2)
+    b = sum(a, dims=1)
+    @test b[begin] == sum(r)
+end