Writing your own BEAM

https://martin.janiczek.cz/2025/11/09/writing-your-own-beam.html

by cbzbc • 9 months ago

268 34 9 months ago

martin.janiczek.cz

macintux• 8 months ago

Now I'm curious whether Joe Armstrong's original Prolog implementation of the VM is available anywhere, but I doubt it.

rramadass2• 8 months ago

The next best thing : Implementing a Functional Language for Highly Parallel Real Time Applications by J.L.Armstrong et al. (pdf) - https://www.cs.tufts.edu/~nr/cs257/archive/joe-armstrong/erl... Seems like this is the design behind the original JAM VM. The "References" section cites more early work.

See also The Erlang BEAM Virtual Machine Specification by the OG Bogumil Hausman himself ! Note: This document describes BEAM as it was in 1997. BEAM has grown and changed significantly between then and the time this note was added (2012). This information is mainly for historical interest. - https://www.cs-lab.org/historical_beam_instruction_set.html

Together, they should provide a lot of insights into ERTS/BEAM.

lukego• 8 months ago

Joe used to have all that code in his world-readable NFS-mounted home directory. He would just create a new directory for every idea or project. Take it with him from one computer to the next.

I hope that's preserved and one day published as e.g. the old MIT AI lab file system snapshots were.

(Robert Virding or Bjärne Däcker might well have a copy of the Prolog code to share if asked nicely.)

FredPret• 8 months ago

I have learnt to love and embrace the BEAM.

Wikipedia says "Originally BEAM was short for Bogdan's Erlang Abstract Machine, named after Bogumil "Bogdan" Hausman, who wrote the original version, but the name may also be referred to as Björn's Erlang Abstract Machine, after Björn Gustavsson, who wrote and maintains the current version."

Whether the B is for Bogdan or Bjorn, there's something really fun and Space Quest-y about it.

DrewADesign4• 8 months ago

I like to think the B stands for BEAM.

yas_hmaheshwari• 8 months ago

Same here! I also don't want "the facts to come in the way of a good story", and want to believe B is BEAM.

IshKebab4• 8 months ago

Very cliché.

Y_Y• 8 months ago

It obviously stands for "Benoit B Mandelbrot"

Alupis3• 8 months ago

The BEAM is fascinating for many reasons, including being register-based.

I really just wish the BEAM was portable in the way the JVM is. The BEAM hooks into so many system libraries, you must compile it on every flavor of linux instead of just unpacking a tarball.

This means you either must use your distro package manager's version, or compile from scratch. If you want to control the exact version that's being used across your team (via `asdf` or similar), this practically means you'll end up compiling the BEAM over and over...

hamandcheese4• 8 months ago

Perhaps you should give Nix a try :)

Alupis3• 8 months ago

Correct me if I'm wrong, but you'd still have to compile it from source on nix, no?

On my relatively powerful workstation, Erlang/BEAM takes about 7 minutes to compile.

We're working around this currently by having a fat devcontainer image, pre-built with Erlang inside (from source) by our CI. It chews through CI minutes unavoidably due to how docker layer caching works.

It would be awesome to just download and unpack a tarball, regardless of which distro you're using.

IshKebab4• 8 months ago

Nix is enormously complicated, kind of unstable and not well documented.

I get that if you've gone through the pain of learning it you get a system with some very nice properties. But casually suggesting "maybe try nix" is a bit like telling someone who wants to listen to Mozart "maybe try playing a piano".

valorzard• 8 months ago

You want https://github.com/burrito-elixir/burrito

harrisi• 8 months ago

Burrito works very well in my experience. I've used it for distributing an implementation of breakout in Elixir with OpenGL and Metal rendering backends as a binary. Pretty neat!

Alupis3• 8 months ago

This is very neat, thanks for the link!

Digging into it, you can get "universal" BEAM tarballs from here[1]. It links against muslibc and appears to bring it's own openssl. Very cool.

[1] https://beammachine.cloud/

lpil• 8 months ago

The BEAM hooks into so many system libraries, you must compile it on every flavor of linux instead of just unpacking a tarball.

This isn't true, one can statically compile the BEAM for Linux exactly the same as the JVM. Here's an example: https://github.com/yoshi-monster/static_erlang/

MisterTea2• 8 months ago

The BEAM is fascinating for many reasons, including being register-based. I really just wish the BEAM was portable in the way the JVM is.

Inferno is both register based and highly portable using the same tool chain as Plan 9 which runs seamlessly across multiple architectures. This eventually evolved into the Go tooling as Rob Pike came up with the Plan 9 design and worked on it with Ken Thompson. https://seh.dev/go-legacy/

Unfortunately Inferno was never fully completed and bit-rotted a bit but it still builds on systems with 32 bit support. There are various forks and even an attempted 64 bit version. To me its a great design as it not only runs on bare metal but also has a hosted option so it runs under Plan 9, Windows, MacOS/Unix/BSD/Linux. Talk about a portable OS...

ux266478• 8 months ago

To be clear, Inferno is the operating system. The virtual machine is Dis. There exist a few examples[1] of 64-bit Dis, but usually the problem people run into is making the Limbo[2] compiler spit out 64-bit code.

It's rather unfortunate, Inferno is a really nice system with a lot of interesting reference stuff implemented like a typed shell[3]. It's also Plan 9 in a box with all the accoutrements, and knowers will have jumped out of their seat at the implication. I can't understate how cool the Inferno system is.

[1] https://github.com/Plan9-Archive/9ferno

[2] https://en.wikipedia.org/wiki/Limbo_(programming_language)

[3] https://inferno-os.org/inferno/man/2/alphabet-intro.html

rramadass2• 8 months ago

Nice. Have to spend some time reading it but i really like the minimalistic and clean design of your site content. No unnecessary colors/asides/verbiage/etc. nonsense but THE content and only the content presented directly.

A suggestion: Please add a "Overview" section in the beginning to provide the big-picture architecture since without that it would be hard to understand your code.

PS: In case you didn't see it, my comment here mentions some documents that you might find useful for your implementation - https://news.ycombinator.com/item?id=45883694

sublimefire• 8 months ago

Did not know about it much before but apparently was doing something similar (in spirit) when experimenting with simple task execution queues in go. This is quite interesting and given that hot code reloading is a thing in beam it might be something to explore further.

malkosta• 8 months ago

Beautiful! :clap:

shreddit• 8 months ago

Clicked on the link because I don’t know what a “BEAM” is, was not disappointed

Writing your own BEAM

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