Merge pull request #16 from SciML/ap/similar

feat: implement `similar`

Author: ChrisRackauckas

Project.toml

@@ -1,7 +1,7 @@
 name = "FastAlmostBandedMatrices"
 uuid = "9d29842c-ecb8-4973-b1e9-a27b1157504e"
 authors = ["Avik Pal"]
-version = "0.1.3"
+version = "0.1.4"
 
 [deps]
 ArrayInterface = "4fba245c-0d91-5ea0-9b3e-6abc04ee57a9"

src/FastAlmostBandedMatrices.jl

@@ -126,6 +126,14 @@ end
 @inline Base.eltype(::AlmostBandedMatrix{T}) where {T} = T
 @inline Base.IndexStyle(::Type{<:AlmostBandedMatrix}) = IndexCartesian()
 
+# If dims is provided we will construct a Matrix but other invokations should return a
+# AlmostBandedMatrix
+function Base.similar(A::AlmostBandedMatrix, ::Type{T}) where {T}
+    bands = similar(A.bands, T)
+    fill = similar(A.fill, T)
+    return AlmostBandedMatrix{T}(bands, fill)
+end
+
 @inline function colsupport(::AbstractAlmostBandedLayout, A, j)
     l, u = almostbandwidths(A)
     if j ≤ l + u

test/runtests.jl

@@ -17,6 +17,19 @@ using SafeTestsets, Test
         @test almostbandedrank(A) == 2
     end
 
+    @safetestset "similar" begin
+        using FastAlmostBandedMatrices
+
+        A = AlmostBandedMatrix(brand(Float64, 10, 10, 2, 1), rand(Float64, 2, 10))
+
+        @test similar(A) isa AlmostBandedMatrix
+        @test similar(A, Float32) isa AlmostBandedMatrix{Float32}
+
+        fallback = similar(A, Float32, 10, 10)
+        @test fallback isa Matrix{Float32}
+        @test size(fallback) == size(A)
+    end
+
     @safetestset "Copy" begin
         using FastAlmostBandedMatrices