# Where does Julia (ecosystem) provide the greatest speedup, and where does it lag the most behind (compared to e.g. Python)?

**URL:** https://discourse.julialang.org/t/where-does-julia-ecosystem-provide-the-greatest-speedup-and-where-does-it-lag-the-most-behind-compared-to-e-g-python/56565
**Category:** Community
**Created:** [March 5, 2021, 3:22pm UTC](https://discourse.julialang.org/t/where-does-julia-ecosystem-provide-the-greatest-speedup-and-where-does-it-lag-the-most-behind-compared-to-e-g-python/56565 "2021-03-05T15:22:57Z")
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### Author: ![tkf](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tkf/32/17635_2.png) [@tkf](https://discourse.julialang.org/u/tkf)
#### Post date: [March 8, 2021, 5:56pm UTC](https://discourse.julialang.org/t/where-does-julia-ecosystem-provide-the-greatest-speedup-and-where-does-it-lag-the-most-behind-compared-to-e-g-python/56565/38 "2021-03-08T17:56:58Z")

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> [@ChrisRackauckas](#):
>
> If you do need a lower spawn cost, then you can essentially disable the scheduler using tools like:

Since one of the themes in this thread has been the composability of parallel Julia programs, I cannot help but comment that there is a concern in the composability of ThreadingUtilities.jl (and so CheapThreads.jl that depends on it). There is a discussion in: [Overhead of `Threads.@threads` - #16 by tkf](https://discourse.julialang.org/t/overhead-of-threads-threads/53964/16). @Elrod said he had some ideas of fixing it so it may be fixed or mitigated at some point, though.

I think composability for parallel Julia programs will be a community effort. For example, APIs with data races (e.g., a function that mutates global states without holding a lock) cannot be composed with parallel functions. A more subtle example is that, if a package manipulates the scheduling aspect of the task too eagerly, it may not work well in the context of a large application. The basis of composability is the centralized management of computation resources (= CPU + cache). Of course, I think any “hacks” will be justified if it helps you in the end. It is your software, after all. However, I cannot imagine a scenario that the Julia ecosystem evolves into a composable parallel platform without trusting the core parallel task runtime.

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