# How to check if LU factorization failed?

**URL:** <https://discourse.julialang.org/t/how-to-check-if-lu-factorization-failed/5553>\
**Category:** Numerics\
**Tags:** question, linearalgebra\
**Created:** [August 25, 2017, 3:50am UTC](https://discourse.julialang.org/t/how-to-check-if-lu-factorization-failed/5553 "2017-08-25T03:50:26Z")\
**Posts on this page:** 1\
**Showing post:** 14

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**Author:** ![juliohm](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/juliohm/32/215266_2.png) [@juliohm](https://discourse.julialang.org/u/juliohm)\
**Post date:** [August 25, 2017, 3:48pm UTC](https://discourse.julialang.org/t/how-to-check-if-lu-factorization-failed/5553/14 "2017-08-25T15:48:10Z")

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Thank you @fredrikekre, very helpful information again. From what I understood, if I stick with the idea of replacing my `pairwise` implementation above to return a `Symmetric(D)`, I will get into trouble in Julia v0.6.

I won’t change it for now, but it would be great to have these fixed and announced somewhere (perhaps here).

Regarding memory savings, I remember posting a question some time ago about the fact that Symmetric is using the full array instead of just half, @Ralph_Smith did mention that there is support in LAPACK, but no one has had the time to implement it yet:

> [@Symmetric matrices](https://discourse.julialang.org/t/symmetric-matrices/4086/9):
>
> For some operations (esp. Cholesky and triangular solves) LAPACK has routines for rectangular full packed format (newer than the format @nalimilan and @stevengj address above), which enables the use of half the full storage while maintaining efficiency by using Level 3 BLAS/LAPACK kernels. (detaiils [here](http://www.netlib.org/lapack/lapack-3.2.html), about haflway down the page). If these capabilities fit the bill, the price to be paid is in developer time.

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