# "sparse inverse" from sparse Cholesky

**URL:** <https://discourse.julialang.org/t/sparse-inverse-from-sparse-cholesky/63080>\
**Category:** Numerics\
**Tags:** question, linearalgebra, sparse\
**Created:** [June 17, 2021, 12:07pm UTC](https://discourse.julialang.org/t/sparse-inverse-from-sparse-cholesky/63080 "2021-06-17T12:07:10Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Andres\_Legarra](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/andres_legarra/32/8786_2.png) [@Andres\_Legarra](https://discourse.julialang.org/u/Andres_Legarra)\
**Post date:** [June 17, 2021, 12:07pm UTC](https://discourse.julialang.org/t/sparse-inverse-from-sparse-cholesky/63080/1 "2021-06-17T12:07:10Z")

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I am looking for a manner to obtain, from the sparse Cholesky decomposition of sparse A, the “sparse inverse”, i.e. obtaining _only_ the elements in A^{-1} that correspond to the non-null elements in A. This is sometimes known as the Takahashi inverse, and there is an efficient algorithm, see [Functions — cholmod-extra 0.1 documentation](https://cholmod-extra.readthedocs.io/en/latest/functions.html#sparse-inverse) . Any pointer? Thanks.