[ViralBShah]

cholesky and ldlt of a sparse matrix whose index type does not promote with Int to one CHOLMOD takes, such as UInt64, throw a bare TypeError from inside the CHOLMOD.Sparse conversion, where lu names the matrix type. cholesky! and ldlt! reject index types like Int16 that cholesky and ldlt accept.

Before

julia> A = sparse([4.0 1 0; 1 4 1; 0 1 4]);

julia> cholesky(SparseMatrixCSC{Float64,UInt64}(A))
ERROR: TypeError: in Sparse, in Ti, expected Ti<:Union{Int32, Int64}, got Type{UInt64}

julia> cholesky(SparseMatrixCSC{Float64,Int16}(A));   # works

julia> cholesky!(cholesky(A), SparseMatrixCSC{Float64,Int16}(A))
ERROR: TypeError: in Sparse, in Ti, expected Ti<:Union{Int32, Int64}, got Type{Int16}

After

julia> cholesky(SparseMatrixCSC{Float64,UInt64}(A))
ERROR: ArgumentError: matrix type SparseMatrixCSC{Float64, UInt64} not supported: CHOLMOD needs an index type of Int32 or Int64. Try converting its index type to Int first.

julia> cholesky!(cholesky(A), SparseMatrixCSC{Float64,Int16}(A))
SparseArrays.CHOLMOD.Factor{Float64, Int64}
...

The six CHOLMOD.Sparse conversions from a SparseMatrixCSC or a Symmetric/Hermitian view of one computed Ti <: ITypes ? Ti : promote_type(Ti, Int) and passed the result to Sparse{Tv, Ti} unchecked. They now call a helper, cholmod_itype, that does the same promotion and throws the ArgumentError when the result is not in ITypes; the message lists ITypes, which is Int32 alone on a 32-bit build. cholesky!(F, A) and ldlt!(F, A) used to convert A to Sparse{eltype(F), Ti} with A's own index type, which factorize_p! then converted again to the factor's. They now convert straight to the factor's index type, so they accept any integer index type, UInt64 included, as long as the indices fit. This touches dispatch: those two methods now take the index type from F rather than from A.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 94.73%. Comparing base (a5211ce) to head (3ad68c7).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/solvers/cholmod.jl	93.33%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1117   +/-   ##
=======================================
  Coverage   94.72%   94.73%           
=======================================
  Files          16       16           
  Lines       10319    10327    +8     
=======================================
+ Hits         9775     9783    +8     
  Misses        544      544           

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