improve conversion to sparse arrays (#289)

* sparse conversion

* map sparse over components

* move tests up

* Move to package extension and extend issparse

* formatting

* use createinstance

---------

Co-authored-by: Jishnu Bhattacharya <jishnub.github@gmail.com>

Project.toml

@@ -7,17 +7,20 @@ Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
 ConstructionBase = "187b0558-2788-49d3-abe0-74a17ed4e7c9"
 DataAPI = "9a962f9c-6df0-11e9-0e5d-c546b8b5ee8a"
 GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 
 [weakdeps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
 GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 
 [extensions]
 StructArraysAdaptExt = "Adapt"
 StructArraysGPUArraysCoreExt = "GPUArraysCore"
+StructArraysSparseArraysExt = "SparseArrays"
 StructArraysStaticArraysExt = "StaticArrays"
 
 [compat]
@@ -34,6 +37,7 @@ Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
 GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
+LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 OffsetArrays = "6fe1bfb0-de20-5000-8ca7-80f57d26f881"
 PooledArrays = "2dfb63ee-cc39-5dd5-95bd-886bf059d720"
 SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
@@ -43,4 +47,4 @@ TypedTables = "9d95f2ec-7b3d-5a63-8d20-e2491e220bb9"
 WeakRefStrings = "ea10d353-3f73-51f8-a26c-33c1cb351aa5"
 
 [targets]
-test = ["Test", "JLArrays", "StaticArrays", "OffsetArrays", "PooledArrays", "TypedTables", "WeakRefStrings", "Documenter", "SparseArrays", "GPUArraysCore", "Adapt"]
+test = ["Adapt", "Documenter", "GPUArraysCore", "JLArrays", "LinearAlgebra", "OffsetArrays", "PooledArrays", "SparseArrays", "StaticArrays", "Test", "TypedTables", "WeakRefStrings"]

ext/StructArraysSparseArraysExt.jl

@@ -0,0 +1,13 @@
+module StructArraysSparseArraysExt
+
+using StructArrays: StructArray, components, createinstance
+import SparseArrays: sparse, issparse
+
+function sparse(S::StructArray{T}) where {T}
+    sparse_components = map(sparse, components(S))
+    return createinstance.(T, sparse_components...)
+end
+
+issparse(S::StructArray) = all(issparse, components(S))
+
+end

src/StructArrays.jl

@@ -28,6 +28,7 @@ end
 @static if !isdefined(Base, :get_extension)
     include("../ext/StructArraysAdaptExt.jl")
     include("../ext/StructArraysGPUArraysCoreExt.jl")
+    include("../ext/StructArraysSparseArraysExt.jl")
     include("../ext/StructArraysStaticArraysExt.jl")
 end
 

test/runtests.jl

@@ -8,6 +8,7 @@ using DataAPI: refarray, refvalue
 using Adapt: adapt, Adapt
 using JLArrays
 using GPUArraysCore: backend
+using LinearAlgebra
 using Test
 using SparseArrays
 
@@ -613,9 +614,10 @@ end
         A = spzeros(3)
         B = spzeros(3)
         S = StructArray{Complex{eltype(A)}}((A,B))
-        fill!(S, 0)
-        @test all(iszero, A)
-        @test all(iszero, B)
+        fill!(S, 2+3im)
+        @test all(==(2), A)
+        @test all(==(3), B)
+        @test issparse(S)
     end
 end
 
@@ -1144,6 +1146,23 @@ end
     end
 end
 
+@testset "sparse" begin
+    @testset "Vector" begin
+        v = [1,0,2]
+        sv = StructArray{Complex{Int}}((v, v))
+        spv = @inferred sparse(sv)
+        @test spv isa SparseVector{eltype(sv)}
+        @test spv == sv
+    end
+    @testset "Matrix" begin
+        d = Diagonal(Float64[1:4;])
+        sa = StructArray{ComplexF64}((d, d))
+        sp = @inferred sparse(sa)
+        @test sp isa SparseMatrixCSC{eltype(sa)}
+        @test sp == sa
+    end
+end
+
 struct ArrayConverter end
 
 Adapt.adapt_storage(::ArrayConverter, xs::AbstractArray) = convert(Array, xs)