# Inlining behavior: constant prop. fails, I need help in understanding "why"

**URL:** <https://discourse.julialang.org/t/inlining-behavior-constant-prop-fails-i-need-help-in-understanding-why/17134>\
**Category:** Performance\
**Created:** [November 4, 2018, 9:07am UTC](https://discourse.julialang.org/t/inlining-behavior-constant-prop-fails-i-need-help-in-understanding-why/17134 "2018-11-04T09:07:48Z")\
**Posts on this page:** 1\
**Showing post:** 4

<div class="post-metadata">

**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [November 4, 2018, 3:21pm UTC](https://discourse.julialang.org/t/inlining-behavior-constant-prop-fails-i-need-help-in-understanding-why/17134/4 "2018-11-04T15:21:27Z")

</div>

This is how I usually benchmark constant propagation:

```julia
julia> function f(x)
           D = 1
           reconstruct(x, D)
       end
f (generic function with 1 method)

julia> @btime f($x)
  871.847 ns (2 allocations: 112 bytes)
50.48725909006644

```

---

_[View the full topic](https://discourse.julialang.org/t/inlining-behavior-constant-prop-fails-i-need-help-in-understanding-why/17134)._