# Built-in vs. user-defined functions

**URL:** <https://discourse.julialang.org/t/built-in-vs-user-defined-functions/43213>\
**Category:** Performance\
**Tags:** question\
**Created:** [July 17, 2020, 6:36am UTC](https://discourse.julialang.org/t/built-in-vs-user-defined-functions/43213 "2020-07-17T06:36:33Z")\
**Posts on this page:** 1\
**Showing post:** 14

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**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [July 18, 2020, 2:07pm UTC](https://discourse.julialang.org/t/built-in-vs-user-defined-functions/43213/14 "2020-07-18T14:07:50Z")

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> [@Tamas\_Papp](#):
>
> while all the machinery that Base & the standard libraries use to speed things up is available to the user, in a lot of cases it would just complicate the picture in a pedagogical context, especially in an intro course.

(In the case of `sum`, [all you need is `@simd`](https://discourse.julialang.org/t/reduce-vs-foldl-performance-and-precision/43231/7) to match the `Base.sum` performance. But even the `@simd` decoration is a needless complication in an introductory course.)

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