Add extrema support (#392)

On 1.8 `Base.extrema` is `mapreduce` based.

Author: N5N3

src/host/mapreduce.jl

@@ -22,6 +22,9 @@ neutral_element(::typeof(Base.:(*)), T) = one(T)
 neutral_element(::typeof(Base.mul_prod), T) = one(T)
 neutral_element(::typeof(Base.min), T) = typemax(T)
 neutral_element(::typeof(Base.max), T) = typemin(T)
+if VERSION >= v"1.8.0-DEV.1465"
+    neutral_element(::typeof(Base._extrema_rf), ::Type{<:NTuple{2,T}}) where {T} = typemax(T), typemin(T)
+end
 
 # resolve ambiguities
 Base.mapreduce(f, op, A::AnyGPUArray, As::AbstractArrayOrBroadcasted...;

test/testsuite.jl

@@ -17,6 +17,20 @@ using Adapt
 struct ArrayAdaptor{AT} end
 Adapt.adapt_storage(::ArrayAdaptor{AT}, xs::AbstractArray) where {AT} = AT(xs)
 
+test_result(a::Number, b::Number) = a ≈ b
+function test_result(a::AbstractArray{T}, b::AbstractArray{T}) where {T<:Number}
+    collect(a) ≈ collect(b)
+end
+function test_result(a::AbstractArray{T}, b::AbstractArray{T}) where {T<:NTuple{N,<:Number} where {N}}
+    ET = eltype(T)
+    reinterpret(ET, collect(a)) ≈ reinterpret(ET, collect(b))
+end
+function test_result(as::NTuple{N,Any}, bs::NTuple{N,Any}) where {N}
+    all(zip(as, bs)) do (a, b)
+        test_result(a, b)
+    end
+end
+
 function compare(f, AT::Type{<:AbstractGPUArray}, xs...; kwargs...)
     # copy on the CPU, adapt on the GPU, but keep Ref's
     cpu_in = map(x -> isa(x, Base.RefValue) ? x[] : deepcopy(x), xs)
@@ -25,13 +39,7 @@ function compare(f, AT::Type{<:AbstractGPUArray}, xs...; kwargs...)
     cpu_out = f(cpu_in...; kwargs...)
     gpu_out = f(gpu_in...; kwargs...)
 
-    if cpu_out isa Tuple && gpu_out isa Tuple
-        all(zip(cpu_out,gpu_out)) do (cpu, gpu)
-            collect(cpu) ≈ collect(gpu)
-        end
-    else
-        collect(cpu_out) ≈ collect(gpu_out)
-    end
+    test_result(cpu_out, gpu_out)
 end
 
 function compare(f, AT::Type{<:Array}, xs...; kwargs...)

test/testsuite/reductions.jl

@@ -77,7 +77,7 @@ end
     end
 end
 
-@testsuite "reductions/minimum maximum" (AT, eltypes)->begin
+@testsuite "reductions/minimum maximum extrema" (AT, eltypes)->begin
     @testset "$ET" for ET in eltypes
         range = ET <: Real ? (ET(1):ET(10)) : ET
         for (sz,dims) in [(10,)=>[1], (10,10)=>[1,2], (10,10,10)=>[1,2,3], (10,10,10)=>[],
@@ -90,6 +90,11 @@ end
                 @test compare(A->maximum(A), AT, rand(range, sz))
                 @test compare(A->maximum(x->x*x, A), AT, rand(range, sz))
                 @test compare(A->maximum(A; dims=dims), AT, rand(range, sz))
+                if VERSION >= v"1.8.0-DEV.1465"
+                    @test compare(A->extrema(A), AT, rand(range, sz))
+                    @test compare(A->extrema(x->x*x, A), AT, rand(range, sz))
+                    @test compare(A->extrema(A; dims=dims), AT, rand(range, sz))
+                end
             end
         end
 
@@ -98,6 +103,9 @@ end
             if !(ET <: Complex)
                 @test compare((A,R)->minimum!(R, A), AT, rand(range, sz), fill(typemax(ET), red))
                 @test compare((A,R)->maximum!(R, A), AT, rand(range, sz), fill(typemin(ET), red))
+                if VERSION >= v"1.8.0-DEV.1465"
+                    @test compare((A,R)->extrema!(R, A), AT, rand(range, sz), fill((typemax(ET),typemin(ET)), red))
+                end
             end
         end
     end