uproot5 VS PackageCompiler.jl

> I wasn't proposing ROOT to be reimplemented in JS. That was what the GP attributed to me.

Sorry for assuming that. I really felt the pain of thinking of possibility of combining two things I hate so much together (JS+ROOT)

> "Laypeople" may also think that code is optimized to the last cycle in something like HEP simulations. It's made fast enough and the optimization is nowhere near the level of e.g. graphics heavy games.

I understand that in other areas there might be more sophisticated optimizations, but does not change things much inside HEP field community. And it is not optimized only for simulations but for other things too. It is not one problem optimization.

> Real-time usage like high frequency large data collection will probably never happen on the "single language". But I'd guess ROOT is not used at that level either? Also at least last time I checked, ROOT is moving to Python (probably not for the hottest loops of the simulation though).

I did not mean to indicate that ROOT is being used to handle the online processing (In HEP terms). It is usually handled via optimized C++ compiled code. My idea is that you will probably never use JS or any interpreted language (or anything other than C++ to be pessimistic) for that. ROOT at the end of the day is much closer to C++ than anything else. So learning curve wouldn't be that much if you come with some C++ knowledge initially.

> Also at least last time I checked, ROOT is moving to Python (probably not for the hottest loops of the simulation though).

I think you mean PyROOT [1]? This is the official python ROOT interface It provides a set of Python bindings to the ROOT C++ libraries, allowing Python scripts to interact directly with ROOT classes and methods as if they were native Python. But that does not represent and re-writing. It makes things easier for end users who are doing analysis though, while be efficient in terms of performance, especially for operations that are heavily optimized in ROOT.

There is also uproot [2] which is a purely Python-based reader and writer of ROOT files. It is not a part of the official ROOT project and does not depend on the ROOT libraries. Instead, uproot re-implements the I/O functionalities of ROOT in Python. However, it does not provide an interface to the full range of ROOT functionalities. It is particularly useful for integrating ROOT data into a Python-based data analysis pipeline, where libraries like NumPy, SciPy, Matplotlib, and Pandas ..etc are used.

> Off-topic: C++ interpretation like done in ROOT seems like a really bad idea.)

I will agree with you. But to be fair the purpose of ROOT is interactive data analysis but over the decades a lot of things gets added, and many experiments had their own soft forks and things started to get very messy quickly. So that there is no much inertia to fix problems and introduce improvements.

[1] https://root.cern/manual/python/

[2] https://github.com/scikit-hep/uproot5

Besides PyROOT, you can also use uproot to read ROOT files, if you want to avoid the ROOT-dependency. The current version (uproot4) does not yet support writing ROOT files, but the previous/deprecated version (uproot3) does. (Please note: uproot is not maintained by the ROOT project team).

Yes, julia can be called from other languages rather easily, Julia functions can be exposed and called with a C-like ABI [1], and then there's also various packages for languages like Python [2] or R [3] to call Julia code.

With PackageCompiler.jl [4] you can even make AOT compiled standalone binaries, though these are rather large. They've shrunk a fair amount in recent releases, but they're still a lot of low hanging fruit to make the compiled binaries smaller, and some manual work you can do like removing LLVM and filtering stdlibs when they're not needed.

Work is also happening on a more stable / mature system that acts like StaticCompiler.jl [5] except provided by the base language and people who are more experienced in the compiler (i.e. not a janky prototype)

[1] https://docs.julialang.org/en/v1/manual/embedding/

[2] https://pypi.org/project/juliacall/

[3] https://www.rdocumentation.org/packages/JuliaCall/

[4] https://github.com/JuliaLang/PackageCompiler.jl

[5] https://github.com/tshort/StaticCompiler.jl

One of Julia's Achilles heels is standalone, ahead-of-time compilation. Technically this is already possible [1], [2], but there are quite a few limitations when doing this (e.g. "Hello world" is 150 MB [7]) and it's not an easy or natural process.

The immature AoT capabilities are a huge pain to deal with when writing large code packages or even when trying to make command line applications. Things have to be recompiled each time the Julia runtime is shut down. The current strategy in the community to get around this seems to be "keep the REPL alive as long as possible" [3][4][5][6], but this isn't a viable option for all use cases.

Until Julia has better AoT compilation support, it's going to be very difficult to develop large scale programs with it. Version 1.9 has better support for caching compiled code, but I really wish there were better options for AoT compiling small, static, standalone executables and libraries.

[1]: https://julialang.github.io/PackageCompiler.jl/dev/

Doesn’t work on Windows, but https://github.com/JuliaLang/PackageCompiler.jl does.

Also, you can precompile a whole package and just ship the binary. We do this all of the time.

https://github.com/JuliaLang/PackageCompiler.jl

And getting things precompiled: https://sciml.ai/news/2022/09/21/compile_time/

You can have a look at PackageCompiler.jl

I think by PackageManager here you mean package compiler, and yes these improvements do not need a 2.0. v1.8 included a few things to in the near future allow for building binaries without big dependencies like LLVM, and finishing this work is indeed slated for the v1.x releases. Saying "we are not doing a 2.0" is precisely saying that this is more important than things which change the user-facing language semantics.

And TTFP does need to be addressed. It's a current shortcoming of the compiler that native and LLVM code is not cached during the precompilation stages. If such code is able to precompile into binaries, then startup time would be dramatically decreased because then a lot of package code would no longer have to JIT compile. Tim Holy and Valentin Churavy gave a nice talk at JuliaCon 2022 about the current progress of making this work: https://www.youtube.com/watch?v=GnsONc9DYg0 .

This is all tied up with startup time and are all in some sense the same issue. Currently, the only way to get LLVM code cached, and thus startup time essentially eliminated, is to build it into what's called the "system image". That system image is the binary that package compiler builds (https://github.com/JuliaLang/PackageCompiler.jl). Julia then ships with a default system image that includes the standard library in order to remove the major chunk of code that "most" libraries share, which is why all of Julia Base works without JIT lag. However, that means everyone wants to have their thing, be it sparse matrices to statistics, in the standard library so that it gets the JIT-lag free build by default. This means the system image is huge, which is why PackageCompiler, which is simply a system for building binaries by appending package code to the system image, builds big binaries. What needs to happen is for packages to be able to precompile in a way that then caches LLVM and native code. Then there's no major compile time advantage to being in the system image, which will allow things to be pulled out of the system image to have a leaner Julia Base build without major drawbacks, which would then help make the system compile. That will then make it so that an LLVM and BLAS build does not have to be in every binary (which is what takes up most of the space and RAM), which would then allow Julia to much more comfortably move beyond the niche of scientific computing.

You're probably dancing around the edges of what [PackageCompiler.jl](https://github.com/JuliaLang/PackageCompiler.jl) is capable of targeting. There are a few new capabilities coming online, namely [separating codegen from runtime](https://github.com/JuliaLang/julia/pull/41936) and [compiling small static binaries](https://github.com/tshort/StaticCompiler.jl), but you're likely to hit some snags on the bleeding edge.