[ViralBShah]

A Diagonal argument of a sparse broadcast loses the sign of a -0.0 on its diagonal, so the result differs from the dense one.

Before

julia> sparse(ones(2, 2)) ./ Diagonal([-0.0, 1.0])
2×2 Matrix{Float64}:
 Inf  Inf
 Inf   1.0

julia> ones(2, 2) ./ Diagonal([-0.0, 1.0])
2×2 Matrix{Float64}:
 -Inf  Inf
  Inf   1.0

After

julia> sparse(ones(2, 2)) ./ Diagonal([-0.0, 1.0])
2×2 Matrix{Float64}:
 -Inf  Inf
  Inf   1.0

Broadcast and map convert a structured argument with _sparsifystructured. For a Diagonal that went through SparseMatrixCSC(D), which drops the zeros of the diagonal, and the kernel then read the dropped -0.0 as a structural +0.0. Bidiagonal, Tridiagonal and SymTridiagonal arguments already convert with their whole band stored, zeros included, so they were not affected. _sparsifystructured(::Diagonal) now stores the whole diagonal as well. SparseMatrixCSC(D) and sparse(D) are unchanged.

The stored pattern of a zero-preserving result does not change: the kernels store only the nonzero values they compute, so S .* D, S .+ D, S .- D, map(+, S, D) and broadcast!(*, Z, S, D) with zeros (of either sign) on the diagonal have the same nnz and pattern as on main.

Touches dispatch: adds the internal method _sparsifystructured(::Diagonal).

Split from #1022. A bug fix with no change of result type, so a backport candidate.

Written by Claude Code.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.79%. Comparing base (c0f75f0) to head (6129598).
⚠️ Report is 27 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1085      +/-   ##
==========================================
+ Coverage   94.75%   94.79%   +0.03%     
==========================================
  Files          16       16              
  Lines        9885     9886       +1     
==========================================
+ Hits         9367     9371       +4     
+ Misses        518      515       -3     

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[ViralBShah]

Reviewed by Codex at 6129598.

No actionable findings. Materializing the complete diagonal preserves stored signed zeros for the broadcast kernel while leaving implicit off-diagonal zeros implicit.