Update reducedim.jl

Author: N5N3

base/reducedim.jl

@@ -269,11 +269,11 @@ function _mapreducedim!(f, op, R::AbstractArray, A::AbstractArrayOrBroadcasted)
         i1 = first(axes1(R))
         @inbounds for IA in CartesianIndices(indsAt)
             IR = Broadcast.newindex(IA, keep, Idefault)
-            r = R[i1,IR]
-            @simd for i in axes(A, 1)
-                r = op(r, f(A[i, IA]))
-            end
-            R[i1,IR] = r
+            @inline elf(i) = @inbounds f(A[i, IA])
+            ax1 = axes(A, 1)
+            # use mapreduce_impl for performance
+            r = mapreduce_impl(elf, op, ax1, firstindex(ax1), lastindex(ax1))
+            R[i1,IR] = op(R[i1,IR], r)
         end
     else
         @inbounds for IA in CartesianIndices(indsAt)