为什么 julia 需要很长时间才能导入包?

问题描述

我非常关心性能.因此，我将其创建为关于第一次调用或导入包时的延迟的问题.这可能是一个愚蠢的问题.

I am quite concern about performance. So, I am creating this as a question regarding the latency while calling or importing a package at first time. It might be a silly question.

当我第一次为 ex 添加包时，Plots 会消耗一些时间来构建包.再次，当我第一次在我的笔记本上导入包时，也花了一些时间(约 1 分钟)说 Precompiling message导入包后，当我点击 plot() 这也会消耗一些时间(30s - 60s)并最终返回一个绘图.

When the first time I add package for ex, Plots, it consumes some amount of time to build the package. Again when i import the package first time ever on my notebook that also took some time (~1 min) says Precompiling message After importing the package, when I hit plot() this also consumes some time (30s - 60s) and finally returns a plot.

一旦我使用了绘图功能，下次使用时不会花费太多时间来产生结果.

Once I used plot function, whenever I use next time it's not taking much time to produce result.

每当我重新启动笔记本时都会发生这种延迟.

This latency happens whenever I restart a notebook.

我猜它是在执行之前编译函数.因为与 python 不同，julia 不是脚本语言.所以，它应该经过编译.但是，为什么每次重启笔记本都会出现延迟?

I guess it's compiling functions before execution. Because unlike python, julia is not a scripting language. So, it supposed to undergo compilation. But, Why the latency occurs every time when I restart notebook?

无论如何我可以抑制这种延迟吗?无论如何，我可以一次预编译所有内容，以便下次在病房中我看不到任何延迟，而不必担心笔记本或 Julia 终端中的内核重启.为什么会发生延迟?完全是因为编译时间还是取决于我的机器?

Is there anyway I can suppress this latency? Is there anyway I can precompile everything once so that next time on wards I don't see any latency without worrying about kernal restart in notebook or in Julia Terminal. Why does the latency happen? Is it fully because of compilation time or it depends on my machine?

推荐答案

你可以做两件事来减少延迟:

You can do two things to reduce the latency:

1. 使用 Julia 1.5.0(截至今天的测试版)——它动态地允许对包使用不同的优化级别，Plots.jl 正在利用它来减少首次绘图的时间超过一半.这确实是一个唾手可得的成果 - 更新 Julia.以下是我笔记本电脑上的测量结果:

1. Use Julia 1.5.0 (beta as of today) - it dynamically allows to use different optimization levels for packages and Plots.jl is making use of that reducing the time-to-first-plot by more than half. This is indeed a low hanging fruit - update the Julia. Here are the measurements on my laptop:

julia> @time using Plots
 16.816181 seconds (14.46 M allocations: 854.353 MiB, 2.31% gc time)

julia> @time Plots.plot(sin.(1:0.25:7))
  4.292128 seconds (4.70 M allocations: 243.866 MiB, 2.01% gc time)
  # this waits another 7s before the plot actually appears on screen

那些时间不是很好，但可以接受.

Those times are not excellent but acceptable.

1. 将 Plots 构建到您的系统映像中(有关详细信息，请参阅 https://julialang.github.io/PackageCompiler.jl/dev/examples/plots/)

1. Build Plots into your system image (for details see https://julialang.github.io/PackageCompiler.jl/dev/examples/plots/)

using PackageCompiler
create_sysimage(:Plots, sysimage_path="sys_plots.so", precompile_execution_file="precompile_plots.jl")

这将您的首次绘图时间缩短到半秒以下.还有一个缺点是 Julia 解释器 (REPL) 需要 400 毫秒以上的时间才能启动，并且您需要使用标志 --sysimage sys_plots.so (或 --sysimage sys_plots.dll 在 Windows 上)在启动 Julia 时.预编译包有时也会带来其他警告(例如，每次更新包都需要重新编译等).