Unfortunate. I've been following the work on it occasionally.

On one hand, it seemed like JIT work was really progressing in high gear until SC requested a new PEP. Also unfortunate, as it seemed like part of the hope for the JIT was that it'd counter the performance penalty from free threading.

On the other, it did feel (to me) like with all the fancy (and definitely cool) optimizations it got (automatic refcount operation removal, new type-based specializations, inplace math operations), the macrobenchmark benefits weren't _that_ exciting for a JIT. It definitely has potential for more, maybe with even fancier optimizations like unboxing ints, but the complexity just keeps going up.

> It said that the PEP was "overly optimistic" about user-visible differences with the JIT enabled.

The JIT is technically generated from the same source as the interpreter loop itself, so originally the differences were extremely unlikely, but I imagine the risk just kept going up as new JIT-only paths and optimizations were introduced.

And politically, I feel like SC’s reasoning was just “this side project has landed in main branch almost by accident and has been stewing without oversight ever since, with no stabilization in sight”; and the latest PEP was probably still too vague, with a lot of “here’s more things we can add to the stew” - so I can understand if SC wasn’t satisfied.

https://github.com/facebookincubator/cinderx might be a better approach.

It's unfortunate that a technically exciting new feature is being killed partly because of what is essentially bureaucracy (and the lack of the developer's personal bandwidth). On the other hand, it's pretty safe to say that the strict adherence to the PEP policy and all of the bureaucracy that comes with it is what makes Python a great language, for better or worse.

Not to say that the technical objections were without merit, they likely very much weren't, and the debugger and instrumentation support and maintenance work sounds fairly painful on its own.

What a shame. The alternative is CinderX? It's slower unless you stick to "Static Python" which is not most python code in the wild.

Assuming that the biggest bang-for-buck of JIT compilation is optimizing hot loops (which is also the biggest bang-for-buck of optimization in every other context as well), and assuming that, per the historical best practices, all hot loops in Python are already written in C (or Rust, these days), this outcome is somewhat what I would expect.

Gonna dump a technical hot take here.

Python is a mature production language with a lot of users. Even before it was huge - like 20 years ago when I was in college - getting a small backwards compatible API change into a python extension module (gnu readline in my case) required convincing GvR personally that the API change was necessary.

Every JIT attempt I've seen for python just tries to cut too deep in the first pass, and scope themselves too large.

I believe any successful attempt at optimizing python performance from JIT will FIRST start with a 100% semantically compatible hidden type model for optimizing object property access and method dispatch.

The single biggest performance delta in most dynamic language jits come from that, not from optimizing guards off of bytecode operations or from compiling to machine code. It's from converting hashtable lookups into constant-time guard + offset lookups.

The hidden type model is also a hard nut to crack. It needs to perserve dict semantics which have very dynamic behaviour via the various `__*__` methods, and handle exotics scope objects since scoped name lookups are the most common ones which have their own exotic behaviours (I remember python providing some ability for callee frames to inspect caller scopes in some limited ways).

> we don't feel we have the personal bandwidth to carry the current version forward

Are the JIT developers the same people who were working on Faster CPython at Microsoft? No surprise that they don't have the same amount of energy to dedicate to the JIT now that it's gone from a full-time job to a hobby project.

Sad to read this. I had hoped that with the advance of AI capabilities, features like this could be prototyped, tested, implemented and shipped even faster. And I was really looking forward to see performance gains for my favourite language.

Where do we go from here? Microsoft did not continue to finance the Faster CPython project and the current speed gains are good, but not what we hoped.

If you look at the reasons for this it seems like a good decision: https://discuss.python.org/t/pep-836-jit-go-brrr-the-path-to...

There are already many way of addressing Python performance (leaving aside whether Python is a good choice if performance matters) such as Cython, Numba, Pypy and C extensions.

Surprising, even though (IIRC) the performance of the JIT was always fairly underwhelming.

What about the other major change to Python's implementation: free threading? Has it lived up to expectations? I assume it's not also in doubt, despite Guido recently saying "Personally I wish we’d stuck with the GIL"? [0]

[0] https://discuss.python.org/t/pep-805-safe-parallel-python/10...

From https://discuss.python.org/t/pep-836-jit-go-brrr-the-path-to... :

> We want the PEP to be clear that it’s ultimately the JIT team’s responsibility to find solutions for these packages and tools, and how to deal with situations where a tool can’t be supported or made to work

Is it just me or is this absurdly impossible, to the point of willfully killing the project? Committing a team of brilliant compiler engineers to doing free consulting ad infinitum for every bit of tooling in the world, however hacked-together?

The alternative would be to have the bravery to say: this is the way forward to keep this language relevant into the future, and as a steering committee we collectively own that some tooling may be out of date. Instead, this is a signal that Python is going to rest on its laurels for a very long time.

A sad day for CPython but it doesn't have to be a sad day for Python. There is a fully maintained implementation of Python 3.13 that has an advanced JIT compiler. Once your Python warms up it can be 4x faster or higher (depending on what your program is doing). That implementation is called GraalPy and it builds on the JVM:

https://graalpy.org/

A bit like Chrome there's a fully open source version and a proprietary version with a few extra bells and whistles, but the latter is entirely free for both open and commercial usage (you can't redistribute it for a fee). So you may as well use it.

It has other interesting features

• Scalable pauseless GC

• Single binary distribution of Python programs (like Go)

• Fancy and optimized interop with other languages including Java, JavaScript, Kotlin, Ruby and any other Truffle language.

• Supports native extensions. Tested and works with common libs like SciPy, NumPy, PyTorch, Pandas etc: https://graalpy.org/python-developers/compatibility/

• They're working on a GIL-free mode

In recent weeks there has been a release of a new web framework for Python that only runs on GraalPy, called Pyronaut (https://pyronaut.io/). It takes advantage of JVM interop to expose the Micronaut framework, which is similar to Spring for those who know it. Thanks to the JIT and well optimized base libraries it runs extremely fast, being about 3x faster than FastAPI+Granian, or 7x faster than Flask+Gunicorn and having many more features.

https://www.youtube.com/watch?v=zo6L7bxn4OY

(that was presented at Devoxx but the Pyronaut devs will start touring Python specific conferences soon)

So although CPython may not have made it past the JIT milestone, that doesn't mean Python as a language or community has to fail it. It does require openness to alternative implementations, but historically Pythonistas have been fairly good about that (e.g. Pypy was embraced back when it was more active).

This stuff does require you to accept that it's made by Oracle, but as it's open source, that should be OK.

Disclosure: I sit next to some of the people who work on this stuff.

It seems like such a failing and waste of human life that we spend all this time waiting around for python when the JS engines are so cutting edge.

I hope it does not lead to performance issues later. Python is already famous for being slower than compiled languages.

What’s the latest on getting rid of the GIL? Did that work out?

It doesn’t matter. Just write it in Rust. AI will make Python less relevant in the future.

The Rust based Python3 port can keep it and it can still be far more secure than CPython. Not everything it's JIT'ted on RustPython, it's ondemand per function, you have to enable it explicitly.

Interesting, makes sense. JIT in CPython main is a big deal, glad they’re proceeding with caution. Overall looks like they added it as an experimental feature for two years, then decided to back it out. Perfectly reasonable outcome.

This is pretty bittersweet to see.

Python is my favorite language, but I'm honestly tired of having to rewrite performance bottlenecks in Cython or Rust all the time. When the Faster CPython project started with Microsoft's backing, I was really excited. Mark Shannon had that plan promising huge speedups across a few cycles, and while that clearly turned out to be much harder than anticipated, the team still kept pushing forward to deliver a real JIT.

Seeing all of that get bogged down in committee bureaucracy now is just frustrating.

I have a lot of respect for the core devs and I know maintaining CPython, and it is a time donation job. It isn't easy. But I feel that over-caution and red tape ends up discouraging serious contributions. They are setting an unreasonably high bar for something that would obviously help the entire ecosystem.

Just think about the sheer amount of electricity and compute power being wasted every single day running inefficient Python across millions of machines worldwide.

Python really deserves a proper JIT. I genuinely hope they reconsider this.

I just use Go and Rust for everything; most of my mobile apps are in Flutter. I don't see any point in using anything else.

for me it's over for python