From 2b24bd7a8d4b8e3a7aea5119c8fbab0298695cb8 Mon Sep 17 00:00:00 2001
From: Milan Bouchet-Valat <nalimilan@club.fr>
Date: Fri, 22 May 2020 14:45:44 +0200
Subject: [PATCH 1/2] Fix minimum and maximum in the presence of missing values

---
 base/reduce.jl |  9 +++++----
 test/reduce.jl | 12 ++++++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/base/reduce.jl b/base/reduce.jl
index 414bac5099f78..20cee1148b27d 100644
--- a/base/reduce.jl
+++ b/base/reduce.jl
@@ -573,10 +573,11 @@ function mapreduce_impl(f, op::Union{typeof(max), typeof(min)},
     simdstop  = start + chunk_len - 4
     while simdstop <= last - 3
         # short circuit in case of NaN
-        v1 == v1 || return v1
-        v2 == v2 || return v2
-        v3 == v3 || return v3
-        v4 == v4 || return v4
+        # === true is there to ignore missing
+        (v1 == v1) === true || return v1
+        (v2 == v2) === true || return v2
+        (v3 == v3) === true || return v3
+        (v4 == v4) === true || return v4
         @inbounds for i in start:4:simdstop
             v1 = _fast(op, v1, f(A[i+0]))
             v2 = _fast(op, v2, f(A[i+1]))
diff --git a/test/reduce.jl b/test/reduce.jl
index 69b8b1911e7ea..ee0566b1e4c7c 100644
--- a/test/reduce.jl
+++ b/test/reduce.jl
@@ -338,6 +338,18 @@ 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)
 
+@testset "maximum/minimum/extrema with missing values" begin
+    for x in (Vector{Union{Int,Missing}}(missing, 10),
+              Vector{Union{Int,Missing}}(missing, 257))
+        @test maximum(x) === minimum(x) === missing
+        @test extrema(x) === (missing, missing)
+        fill!(x, 1)
+        x[1] = missing
+        @test maximum(x) === minimum(x) === missing
+        @test extrema(x) === (missing, missing)
+    end
+end
+
 # any & all
 
 @test @inferred any([]) == false

From 37251935a5542d1df0398cc8547088f4bb2b2fba Mon Sep 17 00:00:00 2001
From: Milan Bouchet-Valat <nalimilan@club.fr>
Date: Sat, 30 May 2020 12:27:09 +0200
Subject: [PATCH 2/2] Fix comment

---
 base/reduce.jl | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/base/reduce.jl b/base/reduce.jl
index 20cee1148b27d..1f67989f5c871 100644
--- a/base/reduce.jl
+++ b/base/reduce.jl
@@ -572,8 +572,7 @@ function mapreduce_impl(f, op::Union{typeof(max), typeof(min)},
     start = first + 1
     simdstop  = start + chunk_len - 4
     while simdstop <= last - 3
-        # short circuit in case of NaN
-        # === true is there to ignore missing
+        # short circuit in case of NaN or missing
         (v1 == v1) === true || return v1
         (v2 == v2) === true || return v2
         (v3 == v3) === true || return v3