add is_lazy_conjugate

Author: MasonProtter

src/ArrayInterface.jl

@@ -841,6 +841,51 @@ end
     return setindex!(A, val; kwargs...)
 end
 
+
+"""
+    is_lazy_conjugate(::AbstractArray)  
+
+Determine if a given array will lazyily take complex conjugates, such as with `Adjoint`. This will work with
+nested wrappers, so long as there is no type in the chain of wrappers such that `parent_type(T) == T`
+
+Examples
+
+    julia> a = transpose([1 + im, 1-im]')
+    2×1 transpose(adjoint(::Vector{Complex{Int64}})) with eltype Complex{Int64}:
+     1 - 1im
+     1 + 1im
+
+    julia> ArrayInterface.is_lazy_conjugate(a)
+    true
+
+    julia> b = a'
+    1×2 adjoint(transpose(adjoint(::Vector{Complex{Int64}}))) with eltype Complex{Int64}:
+     1+1im  1-1im
+
+    julia> ArrayInterface.is_lazy_conjugate(b)
+    false
+
+"""
+is_lazy_conjugate(::T) where {T <: AbstractArray} = _is_lazy_conjugate(T, false)
+
+function _is_lazy_conjugate(::Type{T}, isconj) where {T <: AbstractArray}
+    Tp = parent_type(T)
+    if T !== Tp
+        _is_lazy_conjugate(Tp, isconj)
+    else
+        isconj
+    end
+end
+
+function _is_lazy_conjugate(::Type{T}, isconj) where {T <: Adjoint}
+    Tp = parent_type(T)
+    if T !== Tp
+        _is_lazy_conjugate(Tp, !isconj)
+    else
+        !isconj
+    end
+end
+
 include("ranges.jl")
 include("dimensions.jl")
 include("axes.jl")
@@ -849,6 +894,8 @@ include("indexing.jl")
 include("stridelayout.jl")
 include("broadcast.jl")
 
+
+
 function __init__()
 
     @require SuiteSparse = "4607b0f0-06f3-5cda-b6b1-a6196a1729e9" begin

test/runtests.jl

@@ -3,7 +3,8 @@ using Base: setindex
 using IfElse
 using ArrayInterface: StaticInt, True, False
 import ArrayInterface: has_sparsestruct, findstructralnz, fast_scalar_indexing, lu_instance,
-    device, contiguous_axis, contiguous_batch_size, stride_rank, dense_dims, static, NDIndex
+    device, contiguous_axis, contiguous_batch_size, stride_rank, dense_dims, static, NDIndex,
+    is_lazy_conjugate
 
 
 if VERSION ≥ v"1.6"
@@ -786,4 +787,19 @@ include("dimensions.jl")
     include("broadcast.jl")
 end
 
+using Test
+using ArrayInterface: is_lazy_conjugate
+
+@testset "lazy conj" begin
+    a = rand(ComplexF64, 2)
+    @test is_lazy_conjugate(a) == false
+    b = a'
+    @test is_lazy_conjugate(b) == true
+    c = transpose(b)
+    @test is_lazy_conjugate(c) == true
+    d = c'
+    @test is_lazy_conjugate(d) == false
+    e = permutedims(d)
+    @test is_lazy_conjugate(e) == false
+end