# High Energy Physics (HEP) folks on Julia?

**URL:** <https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330>\
**Category:** Statistics\
**Tags:** question\
**Created:** [September 22, 2018, 7:26am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330 "2018-09-22T07:26:16Z")\
**Posts on this page:** 20\
**Page:** 2

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**Author:** ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)\
**Post date:** [June 23, 2019, 6:34am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/22 "2019-06-23T06:34:04Z")

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Hi I was the one who started this thread haha.

Right, my original problem is that at the moment `UpROOT.jl` doesn’t work reading a tree containing `TLorentzVector`:

```julia
julia> using UpROOT

julia> tfile = TFile(UpROOT.uproot.open("small.root"))
TDirectory(PyObject <ROOTDirectory b'./small.root' at 0x7f20ab9adba8>)

julia> ttree = tfile["tree"] # error

```

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**Author:** ![chakravala](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chakravala/32/6832_2.png) [@chakravala](https://discourse.julialang.org/u/chakravala)\
**Post date:** [June 23, 2019, 11:19am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/23 "2019-06-23T11:19:29Z")

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Very similar to LorentzVectors is my [Grassmann.jl](https://github.com/chakravala/Grassmann.jl) which can do not only Lorentz vectors, but work with any metric or signature with the full geometric algebra of differential forms (still a work in progress, getting ready to release the first draft of the paper to explain it). It also uses static arrays, although it falls back to `MultiVector` types in general, which are a quite large number type… I have plans for more sparse subtypes. Most interestingly, it supports the 5D conformal geometric algebra, which has the geometry of the full Minkowski plane in addition to 3D geometry.

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**Author:** ![JLT](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jlt/32/2777_2.png) [@JLT](https://discourse.julialang.org/u/JLT)\
**Post date:** [October 7, 2019, 9:25pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/24 "2019-10-07T21:25:28Z")

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@oschulz I have no idea how I missed your reply. Sorry for that!

Regarding `SpatialVector`, I initially wanted to implement it as a `StaticArray`, but I remember there were lots of bugs at the time, and I wanted it to behave as a scalar with regards to broadcasting. Additionally, the performance of `LorentzVector`/`SpatialVector` is (was?) in my experience much more deterministic than `StaticArrays` (I played a bit with Pauli/Dirac matrices a few months ago, implemented using `SMatrix`, and I hit some weird performance issues).

So, basically, I chose the simplest and most reliable solution for my needs at the time, but I might reevaluate it now that `StaticArray` is hopefully more stable. I would definitely like to have the free math and composability 🙂

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**Author:** ![JLT](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jlt/32/2777_2.png) [@JLT](https://discourse.julialang.org/u/JLT)\
**Post date:** [October 7, 2019, 9:36pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/25 "2019-10-07T21:36:28Z")

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Thanks, this looks quite interesting!

I actually had some plans to implement spinors / tensors at some point (whenever I need them for my research…). But it seems that our packages have a slightly different focus. Mine is very dumb (by design!) but fast and reliable. It’s a perfect fit for Monte-Carlo simulations, but it wouldn’t do much more than this. Yours seems much more powerful, but I would probably need to carefully read the references before being able to use it!

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**Author:** ![kevinczimmerman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kevinczimmerman/32/13040_2.png) [@kevinczimmerman](https://discourse.julialang.org/u/kevinczimmerman)\
**Post date:** [October 8, 2019, 2:41am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/26 "2019-10-08T02:41:35Z")

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I’m also in the medical imaging field and would love to contribute to a pure Julia Monte-Carlo particle simulator to replace Geant4. If someone gets it started, reach out and I’ll work on contributing.

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**Author:** ![oschulz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oschulz/32/2998_2.png) [@oschulz](https://discourse.julialang.org/u/oschulz)\
**Post date:** [October 8, 2019, 8:12am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/27 "2019-10-08T08:12:10Z")

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> pure Julia Monte-Carlo particle simulator to replace Geant4

That would be awesome to have, but it would be a massive undertaking to develop (and maintain) an MC package that can operate on par with Geant4.

What may be more feasible, short term, is a Julia wrapper for Geant4. I played with that a bit in the past, via Cxx.jl (prototype: [https://github.com/JuliaHEP/Geant4.jl/tree/dev](https://github.com/JuliaHEP/Geant4.jl/tree/dev)). It kinda worked, except for the Geant4 GUI, do some weird dynamic library loading problems.

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**Author:** ![chakravala](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chakravala/32/6832_2.png) [@chakravala](https://discourse.julialang.org/u/chakravala)\
**Post date:** [October 8, 2019, 10:30am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/28 "2019-10-08T10:30:58Z")

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> [@JLT](#):
>
> Yours seems much more powerful, but I would probably need to carefully read the references before being able to use it!

It’s not well documented yet, and some of it is completely new math that hasn’t been used before, especially the way differential operator are incorporated is a new concept. You’ll have to be bold and ask me questions if you want to learn it, or wait until I create some better documentation. We have a dedicated discussion forum also at [bivector.net](http://bivector.net)

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**Author:** ![jstrube](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jstrube/32/525_2.png) [@jstrube](https://discourse.julialang.org/u/jstrube)\
**Post date:** [October 11, 2019, 2:39pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/29 "2019-10-11T14:39:41Z")

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Oh, cool, I had started to think about doing something like that, but I haven’t gotten past [https://github.com/jstrube/Geant4Builder](https://github.com/jstrube/Geant4Builder)

Not sure if that’s useful for you, but if so, I’d be happy to move it over to JuliaHEP.

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**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [October 11, 2019, 3:12pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/30 "2019-10-11T15:12:03Z")

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Builders should rather go to [https://github.com/JuliaPackaging/Yggdrasil/](https://github.com/JuliaPackaging/Yggdrasil/). Libexpat has been already built there, so it can be used as a dependency. You can open a pull request with your current builder and it’ll be taken care of

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**Author:** ![jstrube](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jstrube/32/525_2.png) [@jstrube](https://discourse.julialang.org/u/jstrube)\
**Post date:** [October 11, 2019, 4:32pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/31 "2019-10-11T16:32:42Z")

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Fair point.  
If I recall correctly, I tried using that libexpat, actually, but it wasn’t working. Maybe that problem is resolved now. Will try again, but not for a couple days.

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**Author:** ![jstrube](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jstrube/32/525_2.png) [@jstrube](https://discourse.julialang.org/u/jstrube)\
**Post date:** [October 12, 2019, 1:19am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/32 "2019-10-12T01:19:47Z")

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Started the pull request here:  
[https://github.com/JuliaPackaging/Yggdrasil/pull/134](https://github.com/JuliaPackaging/Yggdrasil/pull/134)

Also have one for LCIO (the file format used in linear collider studies):  
[https://github.com/JuliaPackaging/Yggdrasil/pull/133](https://github.com/JuliaPackaging/Yggdrasil/pull/133)

Unfortunately, Geant4 builds time out on travis…

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<div class="post-metadata">

**Author:** ![oschulz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oschulz/32/2998_2.png) [@oschulz](https://discourse.julialang.org/u/oschulz)\
**Post date:** [October 14, 2019, 9:22am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/33 "2019-10-14T09:22:46Z")

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I’ll be really nice to have Geant4 available in a pre-built fashion!

@jstrube, have you forseen a way for users to declare that they want to use a local version of Geant4, though? That would be vitally important - often, there are collaboration standards on which Geant4 version has to be used. And quite frequently, Geant4 has to be build with different options for different applications. Or there’s already a cluster-wide installation, and one doesn’t want the huge G4 data files in every user’s home … etc.

It would be great to have an environment variable like “PYTHON” and “JUPYTER” to point to an existing installation.

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**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [October 14, 2019, 9:42am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/34 "2019-10-14T09:42:46Z")

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If you need to use a different library you can always override the default one.

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<div class="post-metadata">

**Author:** ![jstrube](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jstrube/32/525_2.png) [@jstrube](https://discourse.julialang.org/u/jstrube)\
**Post date:** [October 14, 2019, 2:15pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/35 "2019-10-14T14:15:47Z")

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Interesting point. I hadn’t thought of that. I was first trying to see if I can use this from cxx at all, but I haven’t even gotten that far.

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**Author:** ![tamasgal](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamasgal/32/27946_2.png) [@tamasgal](https://discourse.julialang.org/u/tamasgal)\
**Post date:** [November 12, 2019, 10:50am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/36 "2019-11-12T10:50:32Z")

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Btw. I’d like to draw you attention to an issue which I opened today in the uproot project. I am planning to start a native Julia project to read ROOT files.

[https://github.com/scikit-hep/uproot/issues/401](https://github.com/scikit-hep/uproot/issues/401)

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<div class="post-metadata">

**Author:** ![oschulz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oschulz/32/2998_2.png) [@oschulz](https://discourse.julialang.org/u/oschulz)\
**Post date:** [November 12, 2019, 12:59pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/37 "2019-11-12T12:59:09Z")

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> I am planning to start a native Julia project to read ROOT files.

That would be awesome! I do plan to maintain and improve [UpROOT.jl](https://github.com/JuliaHEP/UpROOT.jl), but it’s performance is ultimately limited (via uproot) by Python. Depending on the ROOT file (buffer sizes, data types), performance can be excellent or poor, compared to native ROOT. A pure-Julia implementation should be able to consistently outperform native ROOT. 😉 I hope you’re aware that this would be a massive undertaking though, with a moral obligation to support future changes in the way ROOT handles data. 😉

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**Author:** ![tamasgal](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamasgal/32/27946_2.png) [@tamasgal](https://discourse.julialang.org/u/tamasgal)\
**Post date:** [November 12, 2019, 1:20pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/38 "2019-11-12T13:20:40Z")

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Yes I am totally aware of that it’s a massive undertaking. I also hope that I’ll find enough time to keep up…  
I’d rather invest in a native library than wrapping uproot, to be honest. 🙈 Don’t get me wrong, UpROOT.jl is nice to have, but these kind of wrappings of other high level languages is something I naturally do not like in the Julia ecosystem.

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**Author:** ![oschulz](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oschulz/32/2998_2.png) [@oschulz](https://discourse.julialang.org/u/oschulz)\
**Post date:** [November 12, 2019, 2:21pm UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/39 "2019-11-12T14:21:01Z")

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> Don’t get me wrong, UpROOT.jl is nice to have, but these kind of wrappings of other high level languages is something I naturally do not like in the Julia ecosystem.

I wouldn’t go so far as saying that I don’t like wrappers in the ecosystem, but I fully agree with you that native is very much preferable.

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**Author:** ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)\
**Post date:** [November 13, 2019, 8:21am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/40 "2019-11-13T08:21:36Z")

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actually, since it’s such a huge undertake, it is more practical to first implement a subset of the ROOT utility. Since:

1. We will use Julia mostly for analysis (I don’t believe CERN will use Julia to make nanoAOD from miniAOD for exmaple)
2. most of the files will be n-tuples (since you will make some selection and skimming for your lab)
3. We won’t write to ROOT file that often, and we can afford not to be able to process weird streamers class

This is still a lot, considering there’s different decompression algorithms libs to use and we want to implement some smart cache and deal with jagged arrays. But at least this will enable people to start _using_ julia, and feedbacks should keep us going.

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**Author:** ![tamasgal](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tamasgal/32/27946_2.png) [@tamasgal](https://discourse.julialang.org/u/tamasgal)\
**Post date:** [November 13, 2019, 9:26am UTC](https://discourse.julialang.org/t/high-energy-physics-hep-folks-on-julia/15330/41 "2019-11-13T09:26:31Z")

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Yes exactly. I am planning to cover only the I/O part and focus on what we (KM3NeT) need since my time is also quite limited, but I need this desperately.

Currently we have a Python framework ([km3py / km3pipe · GitLab](https://git.km3net.de/km3py/km3pipe)) which can convert our ROOT structures to HDF5, but it depends on a huge C++/ROOT based framework and of course ROOT itself. It’s also not as fast as it could be…  
For a big part of the collaboration (which works Python/Julia/nonROOTstuff), this means that every now and then huge amounts of MC productions needs to be converted to HDF5 on clusters and of course also the raw data which we take with the detector, using this chain of libraries. I (and all of us I guess) would like to simply access the information in these ROOT files directly.

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