domain promotion for cached operator (#186)

Author: jishnub

src/Caching/matrix.jl

@@ -1,5 +1,5 @@
 CachedOperator(::Type{Matrix},op::Operator;padding::Bool=false) =
-    CachedOperator(op,Array{eltype(op)}(0,0),padding)
+    CachedOperator(op,Array{eltype(op)}(undef,0,0),padding)
 
 
 # Grow cached operator

src/LinearAlgebra/helper.jl

@@ -200,7 +200,7 @@ function unsafe_resize!(W::AbstractMatrix,n::Integer,::Colon)
         W[1:n,:]
     else
         m=size(W,2)
-        ret=Matrix{eltype(W)}(n,m)
+        ret=Matrix{eltype(W)}(undef, n,m)
         ret[1:N,:] = W
         ret
     end

src/Operators/general/CachedOperator.jl

@@ -1,11 +1,5 @@
-
-
 export cache
 
-
-
-
-
 ## CachedOperator
 
 mutable struct CachedOperator{T<:Number,DM<:AbstractMatrix,M<:Operator,DS,RS,BI} <: Operator{T}
@@ -85,7 +79,7 @@ function Base.getindex(B::CachedOperator,k::AbstractRange,j::AbstractRange)
         resizedata!(B,maximum(k),maximum(j))
         B.data[k,j]
     else
-        Matrix{eltype(B)}(length(k),length(j))
+        Matrix{eltype(B)}(undef, length(k),length(j))
     end
 end
 
@@ -114,17 +108,21 @@ end
     end
  end
 
-
-
-
-
-
 resizedata!(B::CachedOperator,::Colon,m::Integer) = resizedata!(B,size(B,1),m)
 resizedata!(B::CachedOperator,n::Integer,::Colon) = resizedata!(B,n,size(B,2))
 
-
 function mul_coefficients(B::CachedOperator,v::AbstractVector{T}) where T<:Number
     resizedata!(B,:,length(v))
 
     B.data*pad(v,size(B.data,2))
 end
+
+function promotedomainspace(C::CachedOperator,sp::Space)
+    C2 = promotedomainspace(C.op, sp)
+    cache(C2)
+end
+
+function promoterangespace(C::CachedOperator,sp::Space)
+    C2 = promoterangespace(C.op, sp)
+    cache(C2)
+end

test/SpacesTest.jl

@@ -3,6 +3,7 @@ import ApproxFunBase: PointSpace, HeavisideSpace, PiecewiseSegment, dimension, V
 using ApproxFunOrthogonalPolynomials
 using StaticArrays
 using BandedMatrices: rowrange, colrange, BandedMatrix
+using LinearAlgebra
 
 @testset "Spaces" begin
     @testset "PointSpace" begin
@@ -125,6 +126,16 @@ using BandedMatrices: rowrange, colrange, BandedMatrix
             @test f(1) == 1
             @test f(4) == 0
         end
+
+        @testset "CachedOperator" begin
+            s = PointSpace(1:3)
+            Mop = Multiplication(Fun(s, 1:3))
+            C = cache(Mop) : s → s
+            @test C isa ApproxFunBase.CachedOperator
+            CM = AbstractMatrix(C[:, :])
+            @test CM == Diagonal(1:3)
+            @test size(C[1:0, 1:0]) == (0, 0)
+        end
     end
 
     @testset "DiracSpace" begin
@@ -387,6 +398,16 @@ using BandedMatrices: rowrange, colrange, BandedMatrix
             @test (@inferred BandedMatrix(S)) == (@inferred Matrix(S))
         end
 
+        @testset "CachedOperator" begin
+            C = cache(Derivative())
+            C = C : Chebyshev() → Ultraspherical(2)
+            D = Derivative() : Chebyshev() → Ultraspherical(2)
+            @test C[1:2, 1:0] == D[1:2, 1:0]
+            @test C[1:10, 1:10] == D[1:10, 1:10]
+            for col in 1:5, row in 1:5
+                @test C[row, col] == D[row, col]
+            end
+        end
 
         @testset "istriu/istril" begin
             for D in Any[Derivative(Chebyshev()),