# Is \` SuiteSparse.CHOLMOD.ldlt\` working correctly?

**URL:** <https://discourse.julialang.org/t/is-suitesparse-cholmod-ldlt-working-correctly/78951>\
**Category:** General Usage\
**Created:** [April 3, 2022, 3:43pm UTC](https://discourse.julialang.org/t/is-suitesparse-cholmod-ldlt-working-correctly/78951 "2022-04-03T15:43:57Z")\
**Posts on this page:** 2\
**Page:** 1

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**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, 3:43pm UTC](https://discourse.julialang.org/t/is-suitesparse-cholmod-ldlt-working-correctly/78951/1 "2022-04-03T15:43:57Z")

</div>

I have a sparse matrix, symmetric, real. Dimension 101680 , number of non zeros ~6M.  
Calling `cholesky` takes around 11 seconds.

```julia
@time K = SuiteSparse.CHOLMOD.cholesky(K)

```

Calling `ldlt` results in several minutes of “nothing happening”, by the end of which there is still no result.

```julia
@time K = SuiteSparse.CHOLMOD.ldlt(K)

```

I wonder if anyone has been successful using this solver?

Edit: ldlt took almost half an hour.

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<div class="post-metadata">

**Author:** ![lucasbanting](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/lucasbanting/32/30936_2.png) [@lucasbanting](https://discourse.julialang.org/u/lucasbanting)\
**Post date:** [May 14, 2023, 2:17pm UTC](https://discourse.julialang.org/t/is-suitesparse-cholmod-ldlt-working-correctly/78951/2 "2023-05-14T14:17:48Z")

</div>

I have had success with ldlt, but if your matrix is SPD you should use cholesky. I’m not 100% sure if this is still the case, but I believe suitepsarse cholesky has a supernodal implementation, while ldlt does not.