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Implement vector indexing for SDiagonal with statically sized indices #926

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Implement vector indexing for SDiagonal with statically sized indices #926

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6f5c862
axes(::SDiagonal) is statically sized
jishnub Jun 16, 2021
9dd183d
invoke instead of duplicating getindex
jishnub Jun 27, 2022
095186a
check for axes inference
jishnub Jun 28, 2022
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6 changes: 6 additions & 0 deletions src/SDiagonal.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,10 @@ SDiagonal(a::StaticMatrix{N,N,T}) where {N,T} = Diagonal(diag(a))
size(::Type{<:SDiagonal{N}}) where {N} = (N,N)
size(::Type{<:SDiagonal{N}}, d::Int) where {N} = d > 2 ? 1 : N

Base.axes(D::SDiagonal, d) = d <= 2 ? axes(D)[d] : SOneTo(1)

Base.reshape(a::SDiagonal, s::Tuple{SOneTo,Vararg{SOneTo}}) = reshape(a, homogenize_shape(s))
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This is the same as the generic fallback:

StaticArrays.jl/src/abstractarray.jl

Line 190 in 29a76ec

@inline reshape(a::AbstractArray, s::Tuple{SOneTo,Vararg{SOneTo}}) = reshape(a, homogenize_shape(s))
.
Do we really need this method?

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Other than this small point, the PR looks nice 👍 .


# define specific methods to avoid allocating mutable arrays
\(D::SDiagonal, b::AbstractVector) = D.diag .\ b
\(D::SDiagonal, b::StaticVector) = D.diag .\ b # catch ambiguity
Expand Down Expand Up @@ -56,3 +60,5 @@ function inv(D::SDiagonal)
check_singular(D)
SDiagonal(inv.(D.diag))
end

Base.copy(D::SDiagonal) = Diagonal(copy(diag(D)))
18 changes: 18 additions & 0 deletions src/indexing.jl
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Expand Up @@ -377,3 +377,21 @@ Base.unsafe_view(A::AbstractArray, i1::StaticIndexing, indices::StaticIndexing..
# the tuple indices has to have at least one element to prevent infinite
# recursion when viewing a zero-dimensional array (see issue #705)
Base.SubArray(A::AbstractArray, indices::Tuple{StaticIndexing, Vararg{StaticIndexing}}) = Base.SubArray(A, map(unwrap, indices))

###########################################################
# SDiagonal
###########################################################

# SDiagonal uses Cartesian indexing, and the canonical indexing methods shadow getindex for Diagonal
# these are needed for ambiguity resolution
@inline function getindex(D::SDiagonal, i::Int, j::Int)
invoke(getindex, Tuple{Diagonal, Int, Int}, D, i, j)
end
@inline function getindex(D::SDiagonal, i::Int...)
invoke(getindex, Tuple{Diagonal, Vararg{Int}}, D, i...)
end
# Ensure that vector indexing with static types lead to SArrays
@propagate_inbounds function getindex(a::SDiagonal, inds::Union{Int, StaticArray{<:Tuple, Int}, SOneTo, Colon}...)
ar = reshape(a, Val(length(inds)))
_getindex(ar, index_sizes(Size(ar), inds...), inds)
end
11 changes: 11 additions & 0 deletions test/SDiagonal.jl
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Expand Up @@ -70,6 +70,15 @@ using StaticArrays, Test, LinearAlgebra

@test length(m) === 4*4

m2 = SMatrix{4,4}(m)
@test (@inferred axes(m)) === axes(m2)
@test axes(m, 1) === axes(m2, 1)
@test axes(m, 3) == SOneTo(1)

@test m[:, 1] === SVector{4}(m[1,1], 0, 0, 0)
@test m[:, :] === m2
@test m[2, 2, 1] === m[2, 2]

@test_throws Exception m[1] = 1

b = @SVector [2,-1,2,1]
Expand Down Expand Up @@ -114,5 +123,7 @@ using StaticArrays, Test, LinearAlgebra

@test m + zero(m) == m
@test m + zero(typeof(m)) == m

@test copy(m) === m
end
end