# Another post on package compilation time

**URL:** <https://discourse.julialang.org/t/another-post-on-package-compilation-time/42015>\
**Category:** Performance\
**Tags:** compilation, package-compiler\
**Created:** [June 25, 2020, 12:15am UTC](https://discourse.julialang.org/t/another-post-on-package-compilation-time/42015 "2020-06-25T00:15:06Z")\
**Posts on this page:** 1\
**Showing post:** 15

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**Author:** ![s-broda](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/s-broda/32/3946_2.png) [@s-broda](https://discourse.julialang.org/u/s-broda)\
**Post date:** [June 29, 2020, 2:27pm UTC](https://discourse.julialang.org/t/another-post-on-package-compilation-time/42015/15 "2020-06-29T14:27:40Z")

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@Tamas_Papp Turns out this is not all that costly at runtime. I think I’ve found a good compromise: when doing model selection (and only then), I now estimate each model as a subset-GARCH model nested within a larger model determined by a `maxlags` parameter. This effectively “lowers” the type parameters into the value domain temporarily.

Taking a `GARCH(1, 1)` nested in a `TGARCH{5, 5, 5}` as an example, this increases the runtime from around 3 milliseconds to 12 milliseconds on a dataset with ~2k observations. It does, however, avoid the ~500 milliseconds of compilation time, so this is a good tradeoff when estimating many different models, as occurs in model selection. In a fresh session, we now have

```julia
julia> @time selectmodel(TGARCH, BG96; minlags=0, maxlags=3);
  9.977057 seconds (35.13 M allocations: 1.707 GiB, 22.18% gc time)

julia> @time selectmodel(TGARCH, BG96; minlags=0, maxlags=3);
  0.110632 seconds (876.17 k allocations: 108.719 MiB)

```

compared to

```julia
julia> @time selectmodel(TGARCH, BG96; minlags=0, maxlags=3);
 91.165097 seconds (394.59 M allocations: 17.032 GiB, 4.62% gc time)

julia> @time selectmodel(TGARCH, BG96; minlags=0, maxlags=3);
  0.062485 seconds (866.18 k allocations: 82.316 MiB)

```

before. For estimation that does not happen in a model selection context, I still specialize on the type, because one might want to do this thousands of times (e.g., when backtesting or fitting a large-dimensional DCC model that uses univariate models in the marginals), so it makes sense to squeeze out every bit of performance then.

@Albert_Zevelev Thanks a lot for making me re-evaluate this. This really improves the user experience quite substantially. If you want to give it a spin, it’s part of version 1.2.0 which will be available as soon as [https://github.com/JuliaRegistries/General/pull/17176](https://github.com/JuliaRegistries/General/pull/17176) gets merged.

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