From 0c1b1727c66c1bc6d55f1ad011f4fc7dea80d87b Mon Sep 17 00:00:00 2001
From: Michael Abbott <32575566+mcabbott@users.noreply.github.com>
Date: Fri, 6 Jan 2023 00:52:31 -0500
Subject: [PATCH 1/4] extra reducedim_init methods

---
 base/reducedim.jl | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/base/reducedim.jl b/base/reducedim.jl
index dc34b4feb1f6a..d4beccc5f9daf 100644
--- a/base/reducedim.jl
+++ b/base/reducedim.jl
@@ -124,7 +124,9 @@ 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))
+for (f1, f2, initval, typeextreme) in ((:min, :max, :Inf, :typemax), (:max, :min, :(-Inf), :typemin),
+                                       (:(FastMath.min_fast), :(FastMath.max_fast), :Inf, :typemax),
+                                       (:(FastMath.max_fast), :(FastMath.min_fast), :(-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

From cd56650b5f1f0557c0446c99be79f7d9e84b3446 Mon Sep 17 00:00:00 2001
From: Michael Abbott <32575566+mcabbott@users.noreply.github.com>
Date: Fri, 6 Jan 2023 00:53:05 -0500
Subject: [PATCH 2/4] FastMath.maximum_fast + tests

---
 base/fastmath.jl | 12 +++++++++++-
 test/fastmath.jl | 15 +++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/base/fastmath.jl b/base/fastmath.jl
index 5f905b86554f4..0cf22457c158a 100644
--- a/base/fastmath.jl
+++ b/base/fastmath.jl
@@ -84,7 +84,10 @@ const fast_op =
          :sinh => :sinh_fast,
          :sqrt => :sqrt_fast,
          :tan => :tan_fast,
-         :tanh => :tanh_fast)
+         :tanh => :tanh_fast,
+         # reductions
+         :maximum => :maximum_fast,
+         :minimum => :minimum_fast)
 
 const rewrite_op =
     Dict(:+= => :+,
@@ -366,4 +369,11 @@ for f in (:^, :atan, :hypot, :log)
     end
 end
 
+# Reductions
+maximum_fast(a; kw...) = Base.reduce(max_fast, a; kw...)
+minimum_fast(a; kw...) = Base.reduce(min_fast, a; kw...)
+
+maximum_fast(f, a; kw...) = Base.mapreduce(f, max_fast, a; kw...)
+minimum_fast(f, a; kw...) = Base.mapreduce(f, min_fast, a; kw...)
+
 end
diff --git a/test/fastmath.jl b/test/fastmath.jl
index e93fb93330b4f..14b70ecdd40c0 100644
--- a/test/fastmath.jl
+++ b/test/fastmath.jl
@@ -207,6 +207,21 @@ end
         @test @fastmath(cis(third)) ≈ cis(third)
     end
 end
+
+@testset "reductions" begin
+    @test @fastmath(maximum([1,2,3])) == 3
+    @test @fastmath(minimum([1,2,3])) == 1
+    @test @fastmath(maximum(abs2, [1,2,3+0im])) == 9
+    @test @fastmath(minimum(sqrt, [1,2,3])) == 1
+    @test @fastmath(maximum(Float32[4 5 6; 7 8 9])) == 9.0f0
+    @test @fastmath(minimum(Float32[4 5 6; 7 8 9])) == 4.0f0
+
+    @test @fastmath(maximum(Float32[4 5 6; 7 8 9]; dims=1)) == Float32[7.0 8.0 9.0]
+    @test @fastmath(minimum(Float32[4 5 6; 7 8 9]; dims=2)) == Float32[4.0; 7.0;;]
+    @test @fastmath(maximum(abs, [4+im -5 6-im; -7 8 -9]; dims=1)) == [7.0 8.0 9.0]
+    @test @fastmath(minimum(cbrt, [4 -5 6; -7 8 -9]; dims=2)) == cbrt.([-5; -9;;])
+end
+
 @testset "issue #10544" begin
     a = fill(1.,2,2)
     b = fill(1.,2,2)

From 162bb6ca42d845c0f165607433628a38cc3483d3 Mon Sep 17 00:00:00 2001
From: Michael Abbott <32575566+mcabbott@users.noreply.github.com>
Date: Fri, 6 Jan 2023 06:57:52 -0500
Subject: [PATCH 3/4] simpler reducedim_init overload

---
 base/fastmath.jl  | 5 +++++
 base/reducedim.jl | 4 +---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/base/fastmath.jl b/base/fastmath.jl
index 0cf22457c158a..fdcea21c35396 100644
--- a/base/fastmath.jl
+++ b/base/fastmath.jl
@@ -370,10 +370,15 @@ for f in (:^, :atan, :hypot, :log)
 end
 
 # Reductions
+
 maximum_fast(a; kw...) = Base.reduce(max_fast, a; kw...)
 minimum_fast(a; kw...) = Base.reduce(min_fast, a; kw...)
 
 maximum_fast(f, a; kw...) = Base.mapreduce(f, max_fast, a; kw...)
 minimum_fast(f, a; kw...) = Base.mapreduce(f, min_fast, a; kw...)
 
+Base.reducedim_init(f, ::typeof(max_fast), A::AbstractArray, region) =
+    Base.reducedim_init(f, max, A::AbstractArray, region)
+Base.reducedim_init(f, ::typeof(min_fast), A::AbstractArray, region) =
+    Base.reducedim_init(f, min, A::AbstractArray, region)
 end
diff --git a/base/reducedim.jl b/base/reducedim.jl
index d4beccc5f9daf..dc34b4feb1f6a 100644
--- a/base/reducedim.jl
+++ b/base/reducedim.jl
@@ -124,9 +124,7 @@ 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),
-                                       (:(FastMath.min_fast), :(FastMath.max_fast), :Inf, :typemax),
-                                       (:(FastMath.max_fast), :(FastMath.min_fast), :(-Inf), :typemin))
+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

From def00d02cdadb1f02c985ecf52dcf94da3588943 Mon Sep 17 00:00:00 2001
From: Michael Abbott <32575566+mcabbott@users.noreply.github.com>
Date: Fri, 6 Jan 2023 06:58:17 -0500
Subject: [PATCH 4/4] in-place versions

---
 base/fastmath.jl | 15 ++++++++++++++-
 test/fastmath.jl | 10 ++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/base/fastmath.jl b/base/fastmath.jl
index fdcea21c35396..a969bcaaa6ae0 100644
--- a/base/fastmath.jl
+++ b/base/fastmath.jl
@@ -87,7 +87,9 @@ const fast_op =
          :tanh => :tanh_fast,
          # reductions
          :maximum => :maximum_fast,
-         :minimum => :minimum_fast)
+         :minimum => :minimum_fast,
+         :maximum! => :maximum!_fast,
+         :minimum! => :minimum!_fast)
 
 const rewrite_op =
     Dict(:+= => :+,
@@ -381,4 +383,15 @@ Base.reducedim_init(f, ::typeof(max_fast), A::AbstractArray, region) =
     Base.reducedim_init(f, max, A::AbstractArray, region)
 Base.reducedim_init(f, ::typeof(min_fast), A::AbstractArray, region) =
     Base.reducedim_init(f, min, A::AbstractArray, region)
+
+maximum!_fast(r::AbstractArray, A::AbstractArray; kw...) =
+    maximum!_fast(identity, r, A; kw...)
+minimum!_fast(r::AbstractArray, A::AbstractArray; kw...) =
+    minimum!_fast(identity, r, A; kw...)
+
+maximum!_fast(f::Function, r::AbstractArray, A::AbstractArray; init::Bool=true) =
+    Base.mapreducedim!(f, max_fast, Base.initarray!(r, f, max, init, A), A)
+minimum!_fast(f::Function, r::AbstractArray, A::AbstractArray; init::Bool=true) =
+    Base.mapreducedim!(f, min_fast, Base.initarray!(r, f, min, init, A), A)
+
 end
diff --git a/test/fastmath.jl b/test/fastmath.jl
index 14b70ecdd40c0..8755e727db092 100644
--- a/test/fastmath.jl
+++ b/test/fastmath.jl
@@ -220,6 +220,16 @@ end
     @test @fastmath(minimum(Float32[4 5 6; 7 8 9]; dims=2)) == Float32[4.0; 7.0;;]
     @test @fastmath(maximum(abs, [4+im -5 6-im; -7 8 -9]; dims=1)) == [7.0 8.0 9.0]
     @test @fastmath(minimum(cbrt, [4 -5 6; -7 8 -9]; dims=2)) == cbrt.([-5; -9;;])
+
+    x = randn(3,4,5)
+    x1 = sum(x; dims=1)
+    x23 = sum(x; dims=(2,3))
+    @test @fastmath(maximum!(x1, x)) ≈ maximum(x; dims=1)
+    @test x1 ≈ maximum(x; dims=1)
+    @test @fastmath(minimum!(x23, x)) ≈ minimum(x; dims=(2,3))
+    @test x23 ≈ minimum(x; dims=(2,3))
+    @test @fastmath(maximum!(abs, x23, x .+ im)) ≈ maximum(abs, x .+ im; dims=(2,3))
+    @test @fastmath(minimum!(abs2, x1, x .+ im)) ≈ minimum(abs2, x .+ im; dims=1)
 end
 
 @testset "issue #10544" begin