# Performance of map!()

**URL:** <https://discourse.julialang.org/t/performance-of-map/22821>\
**Category:** Performance\
**Created:** [April 5, 2019, 10:07pm UTC](https://discourse.julialang.org/t/performance-of-map/22821 "2019-04-05T22:07:00Z")\
**Posts on this page:** 1\
**Showing post:** 13

<div class="post-metadata">

**Author:** ![tkoolen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tkoolen/32/1603_2.png) [@tkoolen](https://discourse.julialang.org/u/tkoolen)\
**Post date:** [August 23, 2019, 4:03am UTC](https://discourse.julialang.org/t/performance-of-map/22821/13 "2019-08-23T04:03:04Z")

</div>

```julia
julia> @btime $y .= $y.^2
  6.818 ns (0 allocations: 0 bytes)

```

See e.g. [Function calls in global scope, benchmarking, etc - #2 by mbauman](https://discourse.julialang.org/t/function-calls-in-global-scope-benchmarking-etc/27513/2).

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