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Remove zeroing in similar for Hermitian #1455

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Sep 19, 2025
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Remove zeroing in similar for Hermitian #1455

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10 changes: 2 additions & 8 deletions src/symmetric.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -330,14 +330,8 @@ isdiag(A::HermOrSym) = applytri(isdiag, A)

# For A<:Union{Symmetric,Hermitian}, similar(A[, neweltype]) should yield a matrix with the same
# symmetry type, uplo flag, and underlying storage type as A. The following methods cover these cases.
similar(A::Symmetric, ::Type{T}) where {T} = Symmetric(similar(parent(A), T), ifelse(A.uplo == 'U', :U, :L))
# If the Hermitian constructor's check ascertaining that the wrapped matrix's
# diagonal is strictly real is removed, the following method can be simplified.
function similar(A::Hermitian, ::Type{T}) where T
B = similar(parent(A), T)
for i in 1:size(B, 1) B[i, i] = 0 end
return Hermitian(B, ifelse(A.uplo == 'U', :U, :L))
end
similar(A::Symmetric, ::Type{T}) where {T} = Symmetric(similar(parent(A), T), sym_uplo(A.uplo))
similar(A::Hermitian, ::Type{T}) where {T} = Hermitian(similar(parent(A), T), sym_uplo(A.uplo))
# On the other hand, similar(A, [neweltype,] shape...) should yield a matrix of the underlying
# storage type of A (not wrapped in a symmetry type). The following method covers these cases.
similar(A::Union{Symmetric,Hermitian}, ::Type{T}, dims::Dims{N}) where {T,N} = similar(parent(A), T, dims)
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