From e015b3e66def8f0d4e0cb3b116572cad2d5d46a0 Mon Sep 17 00:00:00 2001
From: N5N3 <2642243996@qq.com>
Date: Mon, 3 Jan 2022 11:52:07 +0800
Subject: [PATCH] simplify min/max init

---
 base/reducedim.jl | 47 +++++++++++------------------------------------
 test/reduce.jl    | 20 +++++++-------------
 2 files changed, 18 insertions(+), 49 deletions(-)

diff --git a/base/reducedim.jl b/base/reducedim.jl
index fcf93ed027394c..d9571a575969b0 100644
--- a/base/reducedim.jl
+++ b/base/reducedim.jl
@@ -91,7 +91,6 @@ end
 # reducedim_initarray is called by
 reducedim_initarray(A::AbstractArrayOrBroadcasted, region, init, ::Type{R}) where {R} = fill!(similar(A,R,reduced_indices(A,region)), init)
 reducedim_initarray(A::AbstractArrayOrBroadcasted, region, init::T) where {T} = reducedim_initarray(A, region, init, T)
-# TODO: extend this to minimum and maximum
 reducedim_initarray(A::AbstractArrayOrBroadcasted, region, ::UndefInitializer, ::Type{R}) where {R} = similar(A,R,reduced_indices(A,region))
 # TODO: better way to handle reducedim initialization
 #
@@ -126,45 +125,21 @@ function _reducedim_init(f, op, fv, fop, A, region)
 end
 
 # initialization when computing minima and maxima requires a little care
-for (f1, f2, initval, typeextreme) in ((:min, :max, :Inf, :typemax), (:max, :min, :(-Inf), :typemin))
-    @eval function reducedim_init(f, op::typeof($f1), A::AbstractArray, region)
-        # First compute the reduce indices. This will throw an ArgumentError
-        # if any region is invalid
-        ri = reduced_indices(A, region)
+function reducedim_init(f::F, ::Union{typeof(min),typeof(max)}, A::AbstractArray, region) where {F}
+    # First compute the reduce indices. This will throw an ArgumentError
+    # if any region is invalid
+    ri = reduced_indices(A, region)
 
-        # Next, throw if reduction is over a region with length zero
-        any(i -> isempty(axes(A, i)), region) && _empty_reduce_error()
+    # Next, throw if reduction is over a region with length zero
+    any(i -> isempty(axes(A, i)), region) && _empty_reduce_error()
 
-        # Make a view of the first slice of the region
-        A1 = view(A, ri...)
+    # Make a view of the first slice of the region
+    A1 = view(A, ri...)
 
-        if isempty(A1)
-            # If the slice is empty just return non-view version as the initial array
-            return copy(A1)
-        else
-            # otherwise use the min/max of the first slice as initial value
-            v0 = mapreduce(f, $f2, A1)
-
-            T = _realtype(f, promote_union(eltype(A)))
-            Tr = v0 isa T ? T : typeof(v0)
-
-            # but NaNs and missing need to be avoided as initial values
-            if (v0 == v0) === false
-                # v0 is NaN
-                v0 = $initval
-            elseif isunordered(v0)
-                # v0 is missing or a third-party unordered value
-                Tnm = nonmissingtype(Tr)
-                # TODO: Some types, like BigInt, don't support typemin/typemax.
-                # So a Matrix{Union{BigInt, Missing}} can still error here.
-                v0 = $typeextreme(Tnm)
-            end
-            # v0 may have changed type.
-            Tr = v0 isa T ? T : typeof(v0)
+    # calculate the output type
+    T = promote_typejoin_union(_return_type(f, Tuple{eltype(A)}))
 
-            return reducedim_initarray(A, region, v0, Tr)
-        end
-    end
+    map!(f, reducedim_initarray(A,region,undef,T), A1)
 end
 reducedim_init(f::Union{typeof(abs),typeof(abs2)}, op::typeof(max), A::AbstractArray{T}, region) where {T} =
     reducedim_initarray(A, region, zero(f(zero(T))), _realtype(f, T))
diff --git a/test/reduce.jl b/test/reduce.jl
index 86f12fec745cbc..c1506670d37504 100644
--- a/test/reduce.jl
+++ b/test/reduce.jl
@@ -378,16 +378,13 @@ A = circshift(reshape(1:24,2,3,4), (0,1,1))
 @test size(extrema(A,dims=(1,2,3))) == size(maximum(A,dims=(1,2,3)))
 @test extrema(x->div(x, 2), A, dims=(2,3)) == reshape([(0,11),(1,12)],2,1,1)
 
-# TODO: drop `a′` once `minimum` and `maximum` is fixed
-# (the following test_broken pass)
-function test_extrema(a, a′ = a; dims_test = ((), 1, 2, (1,2), 3))
+function test_extrema(a; dims_test = ((), 1, 2, (1,2), 3))
     for dims in dims_test
         vext = extrema(a; dims)
-        vmin, vmax = minimum(a′; dims), maximum(a′; dims)
-        @test all(x -> isequal(x[1], x[2:3]), zip(vext,vmin,vmax)) || foreach(i -> display(i),(eltype(a), vext,vmin,vmax))
+        vmin, vmax = minimum(a; dims), maximum(a; dims)
+        @test all(x -> isequal(x[1], x[2:3]), zip(vext,vmin,vmax))
     end
 end
-@test_broken minimum([missing BigInt(1)], dims = 2)[1] === missing
 @testset "0.0,-0.0 test for extrema with dims" begin
     @test extrema([-0.0;0.0], dims = 1)[1] === (-0.0,0.0)
     @test tuple(extrema([-0.0;0.0], dims = 2)...) === ((-0.0, -0.0), (0.0, 0.0))
@@ -395,18 +392,15 @@ end
 @testset "NaN/missing test for extrema with dims #43599" begin
     for sz = (3, 10, 100)
         for T in (Int, BigInt, Float64, BigFloat)
-            Aₘ = Matrix{Union{Float64, Missing}}(rand(-sz:sz, sz, sz))
+            Aₘ = Matrix{Union{T, Missing}}(rand(-sz:sz, sz, sz))
             Aₘ[rand(1:sz*sz, sz)] .= missing
-            ATₘ = Matrix{Union{T, Missing}}(Aₘ)
-            test_extrema(ATₘ, Aₘ)
+            test_extrema(Aₘ)
             if T <: AbstractFloat
                 Aₙ = map(i -> ismissing(i) ? T(NaN) : i, Aₘ)
-                ATₙ = map(i -> ismissing(i) ? T(NaN) : i, ATₘ)
-                test_extrema(ATₙ, Aₙ)
+                test_extrema(Aₙ)
                 p = rand(1:sz*sz, sz)
                 Aₘ[p] .= NaN
-                ATₘ[p] .= NaN
-                test_extrema(ATₘ, Aₘ)
+                test_extrema(Aₘ)
             end
         end
     end