Merge pull request #293 from JuliaArrays/safeivdep

add safeivdep

Author: ChrisRackauckas

lib/ArrayInterfaceCore/Project.toml

@@ -1,6 +1,6 @@
 name = "ArrayInterfaceCore"
 uuid = "30b0a656-2188-435a-8636-2ec0e6a096e2"
-version = "0.1.7"
+version = "0.1.8"
 
 [deps]
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

lib/ArrayInterfaceCore/src/ArrayInterfaceCore.jl

@@ -539,4 +539,30 @@ ndims_index(@nospecialize T::Type{<:Base.LogicalIndex}) = ndims(fieldtype(T, :ma
 ndims_index(T::DataType) = 1
 ndims_index(@nospecialize(i)) = ndims_index(typeof(i))
 
+"""
+    instances_do_not_alias(::Type{T}) -> Bool
+
+Is it safe to `ivdep` arrays containing elements of type `T`?
+That is, would it be safe to write to an array full of `T` in parallel?
+This is not true for `mutable struct`s in general, where editing one index
+could edit other indices.
+That is, it is not safe when different instances may alias the same memory.
+"""
+instances_do_not_alias(::Type{T}) where {T} = Base.isbitstype(T)
+
+"""
+    indices_do_not_alias(::Type{T<:AbstractArray}) -> Bool
+
+Is it safe to `ivdep` arrays of type `T`?
+That is, would it be safe to write to an array of type `T` in parallel?
+Examples where this is not true are `BitArray`s or `view(rand(6), [1,2,3,1,2,3])`.
+That is, it is not safe whenever different indices may alias the same memory.
+"""
+indices_do_not_alias(::Type) = false
+indices_do_not_alias(::Type{A}) where {T, A<:Base.StridedArray{T}} = instances_do_not_alias(T)
+indices_do_not_alias(::Type{Adjoint{T,A}}) where {T, A <: AbstractArray{T}} = indices_do_not_alias(A)
+indices_do_not_alias(::Type{Transpose{T,A}}) where {T, A <: AbstractArray{T}} = indices_do_not_alias(A)
+indices_do_not_alias(::Type{<:SubArray{<:Any,<:Any,A,I}}) where {
+  A,I<:Tuple{Vararg{Union{Base.RangeIndex, Base.ReshapedUnitRange, Base.AbstractCartesianIndex}}}} = indices_do_not_alias(A)
+
 end # module

lib/ArrayInterfaceCore/test/runtests.jl

@@ -268,3 +268,18 @@ end
     @test @inferred(ArrayInterfaceCore.ndims_index(1)) == 1
 end
 
+@testset "indices_do_not_alias" begin
+  @test ArrayInterfaceCore.instances_do_not_alias(Float64)
+  @test !ArrayInterfaceCore.instances_do_not_alias(Matrix{Float64})
+  @test ArrayInterfaceCore.indices_do_not_alias(Matrix{Float64})
+  @test !ArrayInterfaceCore.indices_do_not_alias(BitMatrix)
+  @test !ArrayInterfaceCore.indices_do_not_alias(Matrix{Matrix{Float64}})
+  @test ArrayInterfaceCore.indices_do_not_alias(Adjoint{Float64,Matrix{Float64}})
+  @test ArrayInterfaceCore.indices_do_not_alias(Transpose{Float64,Matrix{Float64}})
+  @test ArrayInterfaceCore.indices_do_not_alias(typeof(view(rand(4,4)', 2:3, 1:2)))
+  @test !ArrayInterfaceCore.indices_do_not_alias(typeof(view(rand(7),ones(Int,7))))
+  @test !ArrayInterfaceCore.indices_do_not_alias(Adjoint{Matrix{Float64},Matrix{Matrix{Float64}}})
+  @test !ArrayInterfaceCore.indices_do_not_alias(Transpose{Matrix{Float64},Matrix{Matrix{Float64}}})
+  @test !ArrayInterfaceCore.indices_do_not_alias(typeof(view(fill(rand(4,4),4,4)', 2:3, 1:2)))
+end
+