julia

b8e714df - Less restrictive copyto! signature for triangular matrices (#54649)

Less restrictive copyto! signature for triangular matrices (#54649) On nightly, `copyto!(A::T, B::T) where {T<:UpperTriangular}` checks for the types to be identical. This is overly restrictive, as we only need to check that they are both `UpperTriangular`. This PR relaxes this, which provides a significant performance boost for mismatched types. ```julia julia> using LinearAlgebra julia> A = UpperTriangular(rand(200,200)); B = UpperTriangular(view(rand(200,200),:,:)); julia> @btime copyto!($A, $B); 44.878 μs (0 allocations: 0 bytes) # nightly v"1.12.0-DEV.641" 5.658 μs (0 allocations: 0 bytes) # this PR ``` This PR also changes the behavior when the source and the destination don't have the same size, in which case, `copyto!` should carry out a linear copy and not a Cartesian one, as per its docstring. The previous behavior may be obtained by calling ```julia copyto!(A, CartesianIndices(B), B, CartesianIndices(B)) ``` This change would mean that certain operations that used to work would error now, e.g.: ```julia julia> A = UpperTriangular(zeros(3,3)); B = UpperTriangular(rand(2,2)); julia> copyto!(A, B) ERROR: ArgumentError: cannot set index in the upper triangular part (3, 1) of an UpperTriangular matrix to a nonzero value (0.6898709830945821) ``` whereas this used to carry out a Cartesian copy previously. --------- Co-authored-by: Dilum Aluthge <dilum@aluthge.com>