julia

d749f0eb - Fix zero elements for block-matrix kron involving Diagonal (#55941)

Fix zero elements for block-matrix kron involving Diagonal (#55941) Currently, it's assumed that the zero element is identical for the matrix, but this is not necessary if the elements are matrices themselves and have different sizes. This PR ensures that `kron` for a `Diagonal` has the correct zero elements. Current: ```julia julia> D = Diagonal(1:2) 2×2 Diagonal{Int64, UnitRange{Int64}}: 1 ⋅ ⋅ 2 julia> B = reshape([ones(2,2), ones(3,2), ones(2,3), ones(3,3)], 2, 2); julia> size.(kron(D, B)) 4×4 Matrix{Tuple{Int64, Int64}}: (2, 2) (2, 3) (2, 2) (2, 2) (3, 2) (3, 3) (2, 2) (2, 2) (2, 2) (2, 2) (2, 2) (2, 3) (2, 2) (2, 2) (3, 2) (3, 3) ``` This PR ```julia julia> size.(kron(D, B)) 4×4 Matrix{Tuple{Int64, Int64}}: (2, 2) (2, 3) (2, 2) (2, 3) (3, 2) (3, 3) (3, 2) (3, 3) (2, 2) (2, 3) (2, 2) (2, 3) (3, 2) (3, 3) (3, 2) (3, 3) ``` Note the differences e.g. in the `CartesianIndex(4,1)`, `CartesianIndex(3,2)` and `CartesianIndex(3,3)` elements.