# I need advices to solve Ax=b with Mmap

**URL:** <https://discourse.julialang.org/t/i-need-advices-to-solve-ax-b-with-mmap/28662>\
**Category:** New to Julia\
**Tags:** mmap\
**Created:** [September 11, 2019, 8:07pm UTC](https://discourse.julialang.org/t/i-need-advices-to-solve-ax-b-with-mmap/28662 "2019-09-11T20:07:07Z")\
**Posts on this page:** 1\
**Showing post:** 7

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**Author:** ![c42f](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/c42f/32/52842_2.png) [@c42f](https://discourse.julialang.org/u/c42f)\
**Post date:** [September 12, 2019, 12:25am UTC](https://discourse.julialang.org/t/i-need-advices-to-solve-ax-b-with-mmap/28662/7 "2019-09-12T00:25:41Z")

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I think you could probably do this with an in-place factorization, for example `F = lu!(A_HD)` with an `Mmap`’d array `A`. I’m not sure this is completely allocation-free but it’s a place to start looking.

See also

> [@Inverse with destination?](https://discourse.julialang.org/t/inverse-with-destination/2267):
>
> Dear all, I might be wrong, but in the plethora of BLAS and LAPACK functions, I was not able to find a function of the type inv(dest, X) where X is the matrix to invert and dest is the destination. Any suggestion?

By the way it’s unlikely to be helpful to mmap your vector `b_HD` because it’s so much smaller than the matrix.

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