Support norm for Diagonal (#2860)

* Support norm for Diagonal

* Fix type sig

Author: kshyatt

lib/cublas/linalg.jl

@@ -121,6 +121,7 @@ function LinearAlgebra.norm(x::DenseCuArray{<:Union{Float16, ComplexF16, CublasF
         return invoke(norm, Tuple{AbstractGPUArray, Real}, x, p)
     end
 end
+LinearAlgebra.norm(x::Diagonal{T, <:StridedCuVector{T}}, p::Real=2) where {T<:Union{Float16, ComplexF16, CublasFloat}} = norm(x.diag, p)
 LinearAlgebra.norm2(x::DenseCuArray{<:Union{Float16, ComplexF16, CublasFloat}}) = nrm2(x)
 
 LinearAlgebra.BLAS.asum(x::StridedCuArray{<:CublasFloat}) = asum(length(x), x)

test/libraries/cublas/level1.jl

@@ -152,6 +152,14 @@ k = 13
             CUBLAS.nrm2(dx, result)
             @test norm(x) ≈ result[]
         end
+        @testset "norm of Diagonal" begin
+            x = rand(T, m)
+            dDx = Diagonal(CuArray(x))
+            Dx = Diagonal(x)
+            @test norm(dDx, 1) ≈ norm(Dx, 1)
+            @test norm(dDx, 2) ≈ norm(Dx, 2)
+            @test norm(dDx, Inf) ≈ norm(Dx, Inf)
+        end
     end # level 1 testset
     @testset for T in [Float16, ComplexF16]
         A = CuVector(rand(T, m)) # CUDA.rand doesn't work with 16 bit types yet