# Where is sparse ldlt?

**URL:** <https://discourse.julialang.org/t/where-is-sparse-ldlt/78929>\
**Category:** General Usage\
**Created:** [April 3, 2022, 3:30am UTC](https://discourse.julialang.org/t/where-is-sparse-ldlt/78929 "2022-04-03T03:30:22Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![PetrKryslUCSD](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/petrkryslucsd/32/215825_2.png) [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Post date:** [April 3, 2022, 3:30am UTC](https://discourse.julialang.org/t/where-is-sparse-ldlt/78929/1 "2022-04-03T03:30:22Z")

</div>

The manual says it is in “CHOLMOD library from SuiteSparse” (  
[Linear Algebra · The Julia Language](https://docs.julialang.org/en/v1/stdlib/LinearAlgebra/#LinearAlgebra.ldlt)).  
I cannot find it there:

```julia
julia> SuiteSparse.CHOLMOD.                                                                                                                      
@cholmod_param _copy! factor_to_sparse! print_factor                                      
BUILD_VERSION _extract_args factorize! print_sparse                                      
CHOLMODException _sort_buffers! factorize_p! read_sparse                                       
CHOLMOD_MIN_VERSION _trim_nz_builder! free! scale!                                            
COMMONS aat getLd! sdmult!                                           
Dense allocate_dense get_perm showfactor                                        
Factor allocate_sparse horzcat solve                                             
FactorComponent analyze include sort!                                             
ITypes analyze_p isvalid sparse_to_dense                                   
IndexTypes change_factor! ityp speye                                             
RealHermSymComplexHermF64SSL change_stype! lowrank_reorder spsolve                                           
Sparse check_dense lowrankdowndate ssmult                                            
SparseVecOrMat check_factor lowrankdowndate! symbolic                                          
StridedVecOrMatInclAdjAndTrans check_sparse lowrankupdate symmetry                                          
SuiteSparseStruct dense_to_sparse lowrankupdate! transpose_                                        
VRealTypes dtyp lowrankupdowndate! vertcat                                           
VTypes error_handler norm_dense xtyp                                              
__SPARSE_STYPE_OFFSET eval norm_sparse zeros                                             
__init__ eye ones                                                                              
julia> SuiteSparse.CHOLMOD.

```

The manual also says that it is wrapped in " `Base.SparseArrays.CHOLMOD`". These are the symbols

```julia
julia> SparseArrays.                                                                                                                             
@unarymap_nz2z_z2z _checkargs_sourcecompatworkcolptr_permute! fkeep!                                                    
@unarymap_z2nz _checkargs_sourcecompatworkmat_permute! ftranspose                                                
AbstractSparseArray _checkbuffers ftranspose!                                               
AbstractSparseMatrix _computecolptrs_halfperm! getcolptr                                                 
AbstractSparseMatrixCSC _computecolptrs_permute! getindex_I_sorted                                         
AbstractSparseVector _dense2indval! getindex_I_sorted_bsearch_A                               
AbstractTriangularSparse _dense2sparsevec getindex_I_sorted_bsearch_I                               
AdjOrTransDenseMatrix _densifyfirstnztoend! getindex_I_sorted_linear                                  
AdjOrTransSparseVectorUnion _densifystarttolastnz! getindex_cols                                             
BiTriSym _distributevals_halfperm! getindex_general                                          
DenseInputVecOrMat _fillnonzero! getindex_traverse_col                                     
DenseInputVector _findr getnzval                                                  
DenseMatrixUnion _findz getrowval                                                 
HigherOrderFns _goodbuffers halfperm!                                                 
LowerTriangularPlain _indices ilog2                                                     
LowerTriangularSparse _insert! include                                                   
LowerTriangularWrapped _isgreater_fm indtype                                                   
SparseColumnView _isless_fm is_hermsym                                                
SparseMatrixCSC _ispermutationvalid_permute! issparse                                                  
SparseMatrixCSCSymmHerm _ldiv! iswrsparse                                                
SparseMatrixCSCUnion _lmul! nnz                                                       
SparseMatrixCSCView _logical_index nnz1                                                      
SparseOrTri _mapreducecols! nonzeroinds                                               
SparseTriangular _mapreducerows! nonzeros                                                  
SparseVector _mapreducezeros nzrange                                                   
SparseVectorUnion _maximum nzrangelo                                                 
SparseVectorView _minimum nzrangeup                                                 
TriangularSparse _mul! nzvalview                                                 
UnitDiagonalTriangular _nnz opnormestinv                                              
UpperTriangularPlain _nzvals permute                                                   
UpperTriangularSparse _setindex_scalar! permute_rows!                                             
UpperTriangularWrapped _show_with_braille_patterns possible_adjoint                                          
WrapperMatrixTypes _sparse_copyto! prefer_sort                                               
_Annotated_DenseArrays _sparse_findnextnz prep_sparsevec_copy_dest!                                 
_Annotated_SparseConcatArrays _sparse_findprevnz rangesearch                                               
_Annotated_Typed_DenseArrays _sparse_gen rowvals                                                   
_At_or_Ac_mul_B _sparsem sparse                                                    
_At_or_Ac_mul_B! _sparsesimilar sparse!                                                   
_DenseConcatGroup _sparsevector! sparse_check                                              
_Hermitian_DenseArrays _sparsewrap sparse_check_Ti                                           
_Hermitian_SparseConcatArrays _spdiagm sparse_check_length                                       
_SparseArrays _spdot sparse_compute_reshaped_colptr_and_rowval!                
_SparseConcatArrays _spgetindex sparse_diff1                                              
_SparseConcatGroup _spsetnz_setindex! sparse_diff2                                              
_SpecialArrays _spsetz_setindex! sparse_sortedlinearindices!                               
_StridedOrTriangularMatrix _sum sparsevec                                                 
_Symmetric_DenseArrays _swap! spcolmul!                                                 
_Symmetric_SparseConcatArrays _to_same_csc spdiagm                                                   
_Triangular_DenseArrays blockdiag spdiagm_internal                                          
_Triangular_SparseConcatArrays brailleBlocks spmatmul                                                  
_TypedDenseConcatGroup copyinds! spmatmul1                                                 
_absspvec_hcat densemv spmatmulv                                                 
_absspvec_vcat depth sprand                                                    
_bcast_binary_map dimlub sprandn                                                   
_binarymap dropstored! spzeros                                                   
_binarymap_mode_0! droptol! stuffcol!                                                 
_binarymap_mode_1! dropzeros subvector_shifter!                                        
_binarymap_mode_2! dropzeros! truebools                                                 
_blockdiag estimate_mulsize unchecked_aliasing_permute!                               
_checkargs_permutationsvalid_permute! eval unchecked_noalias_permute!                                
_checkargs_sourcecompatdest_permute! expandptr unwrap                                                    
_checkargs_sourcecompatperms_permute! findnz widelength                                                
julia> SparseArrays.

```

and CHOLMOD is not there.

I think the code changed, while the documentation lags behind. Does anyone know how to locate that solver?

---

<div class="post-metadata">

**Author:** ![skleinbo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/skleinbo/32/36080_2.png) [@skleinbo](https://discourse.julialang.org/u/skleinbo)\
**Post date:** [April 3, 2022, 9:27am UTC](https://discourse.julialang.org/t/where-is-sparse-ldlt/78929/2 "2022-04-03T09:27:46Z")

</div>

It’s still there (`1.7.2`)

```julia
julia> import SparseArrays

julia> SparseArrays.ldlt
ldlt (generic function with 3 methods)

julia> methods(SparseArrays.ldlt)
# 3 methods for generic function "ldlt":
[1] ldlt(M::SymTridiagonal{T, V} where V<:AbstractVector{T}; shift) where T in LinearAlgebra at C:\Users\stephan\AppData\Local\Programs\Julia-1.7.2\share\julia\stdlib\v1.7\LinearAlgebra\src\ldlt.jl:161
[2] ldlt(A::SuiteSparse.CHOLMOD.Sparse; shift, check, perm) in SuiteSparse.CHOLMOD at C:\Users\stephan\AppData\Local\Programs\Julia-1.7.2\share\julia\stdlib\v1.7\SuiteSparse\src\cholmod.jl:1336
[3] ldlt(A::Union{Hermitian{Complex{T}, SparseMatrixCSC{Complex{T}, Int64}}, Hermitian{T, SparseMatrixCSC{T, Int64}}, Symmetric{T, SparseMatrixCSC{T, Int64}}, SparseMatrixCSC{Complex{T}}, SparseMatrixCSC{T}}; kws...) where T<:Real in SuiteSparse.CHOLMOD at C:\Users\stephan\AppData\Local\Programs\Julia-1.7.2\share\julia\stdlib\v1.7\SuiteSparse\src\cholmod.jl:1396

```

but strangely doesn’t appear in the tab-completion. I’ve had that happening recently with another package, which tripped me up too.

This happens apparently because `SparseArrays` extends `ldlt` from `LinearAlgebra`. Why it works this way or doesn’t, I cannot say.

```julia
julia> module ModA
       export f
       f(x::Float64) = x
       end
Main.ModA

julia> module ModB
       import ..ModA: f
       f(x::Int) = x^2
       end
Main.ModB

julia> ModA.

eval f include
julia> ModB.

eval include

julia> ModB.f
f (generic function with 2 methods)

```

---

<div class="post-metadata">

**Author:** ![PetrKryslUCSD](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/petrkryslucsd/32/215825_2.png) [@PetrKryslUCSD](https://discourse.julialang.org/u/PetrKryslUCSD)\
**Post date:** [April 3, 2022, 1:18pm UTC](https://discourse.julialang.org/t/where-is-sparse-ldlt/78929/3 "2022-04-03T13:18:55Z")

</div>

Posted in [https://github.com/JuliaLang/julia/issues/40356](https://github.com/JuliaLang/julia/issues/40356)