>> While the intent is not to call for competing proposals, we believe that now is a good time to discuss and propose alternative proposals as well.
lol
>> For example, rather than proposing one single concrete JIT implementation, it may make more sense for the PEP to describe a JIT infrastructure that can support multiple implementation strategies.
poison-pill requirement
>> We are setting a window of six months for a PEP to be submitted and resolved. If no such PEP is accepted within that window, the JIT code must be removed from the main branch
Without a doubt, a great way to kill any project is to add unrelated and ambitious technical requirements to the project. This opens it up to an avalanche of discussion and feedback and almost certainly will kill it off
No, it’s a simple request to fully investigate the options before committing a massive piece of work to Python. We’ve seen bad implementations of things land before and now live forever. And frankly, if the team can’t pull together a strong maintenance plan, it can’t be allowed to remain in main.
> We’ve seen bad implementations of things land before and now live forever.
Er, doesn't that depend on how leaky the abstraction is? How often have you seen a JITted language be unable to swap in a new JITter due to some sort of unintended coupling?
JIT in CPython has nothing to do with PyPy or GraalPy: it's its own thing. If they can't get a PEP accepted within 6 months then it's best that the code isn't weighing on the main codebase until an approach can be agreed, at which point work integrating it into main can restart. It's not an all-or-nothing situation.
> For that reason, the Steering Council is formally requesting a Standards Track PEP be authored that the community can discuss and the Steering Council can formally accept (or reject), making the case for the JIT as a supported, non-experimental part of CPython: its guarantees, its maintenance commitments, and its impact on redistributors.
I didn't notice the current PEP was a provisional one. Hope the new one gets approved. The experimental JIT was reported to finally breaking even and surpassing the default interpreter just a couple of months ago[1].
>The experimental JIT was reported to finally breaking even and surpassing the default interpreter just a couple of months ago[1].
Thank You. As someone who don't follow python closely I thought their JIT would be similar to what Ruby has.
Not that Ruby YJIT or ZJIT is anywhere close to what JVM provides, but in this case it seems to be quite far ahead of Python.
Which is surprising given how many major companies are using Python. May be because those using Python are not using it as critical part of work unlike Shopify and Stripe which is their core language?
Python software is to a large extent either doing things in not-python (c, c++, rust, etc.) or doing things that are not cpu bound (io bound, async, etc.). If you're cpu bound then you can either take a 2x jit improvement or take a 10x non-python improvement. There's few companies of a scale where the non-hot path cost of 2x cpu is so massive as to be worth caring about.
The python overhead of launching big ML jobs is nontrivial, so I think speeding that up would be meaningful. (I mean the initial tracing and other setup, not things once the GPUs are actually doing the work).
Sure but best case 15% faster clearly isn't worth the complexity of a JIT. It really needs to be at least twice as fast. Pypy pretty much achieves that on average.
Right... but it's still only 15% faster than a simpler alternative. In a language that is 50x slower than the alternatives. Clearly not worth it.
Of course the counterargument is that they'll improve it and maybe in future it will be 100% faster... But that seems pretty dubious given the progress so far.
The post clearly says the intention is to get a formal spec for formal integration.
To leave their experimental phase they have to define some goals to meet and that requires making some architectural choices that still aren't decided.
I suspect the recent "we updated the GC without a PEP and it went live and caused massive issues and we need an emergency point release revert" pushed for a greater degree of process overall.
It's effectively a pause. In a project the size of CPython, and a subproject the complexity of a JIT, you can't continue work on a separate branch/repo without guaranteeing that there will be a massive amount of (both textual and semantic) merge conflicts down the road.
That works, until that inevitable one merge that's harder to fix and takes longer, which in my experience then tends to snowball until it's basically the very merge hell you were trying to avoid. Can't say I've ever had a great experience with long lived feature branches. I can't imagine what it would even look like trying to do this on such a massive project and such an overarching feature.
"Asked to pause development" isn't entirely accurate: they were asked to pause landing new features (as opposed to bug fixes) on the cPython main branch.
... and only until the whole thing can be fully formalized with an approved PEP. I'm no Python insider, but that doesn't sound horribly controversial to me.
And yet, I have a hunch it will piss off a lot of people nonetheless and lead to much outrage and wailing and gnashing of teeth. Hopefully it all works out in the long run.
What a shame it will receive a halt when they where starting to make progress I know that after submitting the pep it will go back to development. But t would have been better to just keep the development and the pep for an actual release or continue and if gets rejected ask them to stop
> What a shame it will receive a halt when they where starting to make progress I know that after submitting the pep it will go back to development.
To be fair, the apparent lack of progress of the JIT before was in part due to the same team improving the base interpreter by 40-50% between 3.10 and 3.14. The JIT implementation was pursuing a moving target. It was not some static milestone. Kudos for them.
That was kind of overdue. The project started five years ago while massively overpromising.
They should perhaps have kept it in a separate branch back then, but now is the next best time.
CPython's selling point was that it is simple, fast enough with C extensions and the code was accessible. Complicating the code base for occasional 50% speedups (and regressions ...) just isn't worth it. There are so many other languages that fill that need.
Now, I hope that the PEP does not overpromise again and is accepted because of Instagram pressure. Instagram can keep its own JIT fork or switch to PHP, Go or whatever.
This hasn't been true for a very long time. Python's major selling points these days are the accessibility of the language and the extensive ecosystem. A vanishingly small fraction of users ever look at the implementation internals. Telling people "if you don't like it, switch to a different language" is particularly unhelpful because rewrites are rather famously expensive. Making things more complicated for the few maintainers, so that they work better for the millions of users, is easily a worthwhile tradeoff.
Who is going to pay for maintaining the massively more complicated implementation though? Microsoft pulled their funding of the Python team, and even if they hadn't I think there's a danger in making Python so complicated that it can no longer be maintained without the backing of some giant corporation.
This isn't really a substantive comment, and to at least one extent it's trivially falsifiable (15 years is before Python 3 became usable, so that alone is a "serious" change in the language).
> pluggable GC and JIT would go along way
One of the points mentioned in the linked discussion is explicitly about ensuring that the JIT design enables multiple implementations.
It seems to have been serious enough; I don't think Python would have succeeded as a language if they hadn't done Python 3.
> Please with your substantive comment comment.
I think binning things as drama isn't substantive, particularly when noting about the linked conversation seems dramatic. I also think they're actually talking about the thing you want (pluggable JIT), so the objection seems incongruous.
> I don't think Python would have succeeded as a language if they hadn't done Python 3.
I assumed Python 2 was pretty much ubiquitous and that the world wasn't adopting Python 3 very quickly for a long time, but I do wonder if the applications I was working with a decade and a half ago (ArcGIS, Blender, Civ4, lots of Red Hat system tools, etc.) biased that viewpoint.
The short answer is that CPython didn't want to break compatibility with lots and lots and lots of Python modules implemented in C, so it was never viable to let PyPy seamlessly replace CPython.
I assume you might mean to ask "why wasn't PyPy adopted in some formal way into CPython" rather than a separate project, for which the answer is at least partially likely to be because it's a completely separate implementation.
People in this thread writing conspiracy theories over the biggest language in the world requiring a bit of bureaucracy lends some credence to the idea that programming is not real engineering.
Right? Every popular language has lots of real problems. Every language has made decisions that people don't like. Every language has varying degrees of imperfect governance. Weirdly enough, most languages even seem to grow at least a small community of dedicated conspiracy theorists. But for whatever reason, it's particularly hard to find level-headed discussions about Python, moreso than js or rust or C++. It's weird.
> While the intent is not to call for competing proposals, we believe that now is a good time to discuss and propose alternative proposals as well.
If I were a contributor I would read such language as saying "we have no respect for you or your intelligence, so we'll just straight up gaslight you and expect you to accept it."
The dictum can't be read literally - it has to be read like the manipulative, narcissist-speak that it is. And what it's telling you is - get out.
I agree.
And the next section is very clear that they want to kill the project.
> For example, rather than proposing one single concrete JIT implementation,
> it may make more sense for the PEP to describe a JIT infrastructure that
> can support multiple implementation strategies.
> Since many different and promising JIT tracing approaches continue to be proposed,
> we believe the infrastructure should make it easy to experiment with and evaluate
> those approaches within CPython rather than be highly coupled with a single strategy.
Allowing multiple strategies is far harder and as far as I know, JIT tracing is still unproven.
I'm a big fan of the pluggable jit strategy (I even gave a brief presentation about it at an earlier pycon). the idea is that you identify the seams in the interpreter where the jit interacts with the main interpreter loop, and then provide a clean mechanism for the built-in jit to be replaced by something else that works with the same api surface. it's a bit harder than letting the built-in jit be tightly coupled to and intertwined with the rest of the interpreter but certainly not far harder, and the work to get this sort of clean separation will help keep the jit maintainable even if there is never a second jit.
I suspect there were people who had alternative proposals which got implicitly blocked by this 5 year effort. Letting a subgroup run wild without proper process is not good for a project this large.
I mean it seems like they want to get a full spec of what JIT should look like in main? given the faff that hapened with the GC removal, I can sort see why they'd want to do this properly. Especially now that it seems like its practical.
It's because they say they don't want to call for competitors and then immediately do so in the second half of the same sentence. It probably wasn't written with bad intent, but you can see why people might find it a strange choice.
Losing development momentum for a beancounting reason like this one is a sure way to kill a project. It works every time. Once development is halted, it is very difficult to pick it back up.
Python isn't a side project to yolo on. Updating the GC without a PEP caused massive issues for actual people using Python. If you want to impact software used by millions of developers then you better be willing to handle a bit of process.
What does "beancounting" mean here? I don't see anything about money or budgets in the announcement. Are you referring to their concerns about the maintainability and complexity of the codebase?
It would make sense if there was any activity on that older post. A 12 hour old post with no comments is dead, linking to it is a waste of time, especially for those who click on it to find 0 comments.
I did click on your link, it was a waste of time and that wasn't very nice.
lol
>> For example, rather than proposing one single concrete JIT implementation, it may make more sense for the PEP to describe a JIT infrastructure that can support multiple implementation strategies.
poison-pill requirement
>> We are setting a window of six months for a PEP to be submitted and resolved. If no such PEP is accepted within that window, the JIT code must be removed from the main branch
so it's going to be removed from the main branch
Er, doesn't that depend on how leaky the abstraction is? How often have you seen a JITted language be unable to swap in a new JITter due to some sort of unintended coupling?
Python JIT history is full of drama, and no, Smalltalk, Common Lisp, Interlisp-D, SELF are just as dynamic if not more.
I haven't said otherwise.
What forever are you talking about? Python removes stuff every single release.
I didn't notice the current PEP was a provisional one. Hope the new one gets approved. The experimental JIT was reported to finally breaking even and surpassing the default interpreter just a couple of months ago[1].
[1] https://fidget-spinner.github.io/posts/jit-on-track.html
Thank You. As someone who don't follow python closely I thought their JIT would be similar to what Ruby has.
Not that Ruby YJIT or ZJIT is anywhere close to what JVM provides, but in this case it seems to be quite far ahead of Python.
Which is surprising given how many major companies are using Python. May be because those using Python are not using it as critical part of work unlike Shopify and Stripe which is their core language?
Of course the counterargument is that they'll improve it and maybe in future it will be 100% faster... But that seems pretty dubious given the progress so far.
To leave their experimental phase they have to define some goals to meet and that requires making some architectural choices that still aren't decided.
Development hasn't been paused (with negative implications).
It's now considered significant enough that they've requested feature freeze in CPython main until governance/process questions are settled.
And yet, I have a hunch it will piss off a lot of people nonetheless and lead to much outrage and wailing and gnashing of teeth. Hopefully it all works out in the long run.
To be fair, the apparent lack of progress of the JIT before was in part due to the same team improving the base interpreter by 40-50% between 3.10 and 3.14. The JIT implementation was pursuing a moving target. It was not some static milestone. Kudos for them.
They should perhaps have kept it in a separate branch back then, but now is the next best time.
CPython's selling point was that it is simple, fast enough with C extensions and the code was accessible. Complicating the code base for occasional 50% speedups (and regressions ...) just isn't worth it. There are so many other languages that fill that need.
Now, I hope that the PEP does not overpromise again and is accepted because of Instagram pressure. Instagram can keep its own JIT fork or switch to PHP, Go or whatever.
It would be nice if cpython opened up a bit, pluggable GC and JIT would go along way towards reducing this manufactured drama.
It wasn't cool to see PyPy or Stackless getting sidelined.
> pluggable GC and JIT would go along way
One of the points mentioned in the linked discussion is explicitly about ensuring that the JIT design enables multiple implementations.
The flippant attitude of cpythons wrt the standard library is also unfortunate.
Please with your substantive comment comment.
> Please with your substantive comment comment.
I think binning things as drama isn't substantive, particularly when noting about the linked conversation seems dramatic. I also think they're actually talking about the thing you want (pluggable JIT), so the objection seems incongruous.
I assumed Python 2 was pretty much ubiquitous and that the world wasn't adopting Python 3 very quickly for a long time, but I do wonder if the applications I was working with a decade and a half ago (ArcGIS, Blender, Civ4, lots of Red Hat system tools, etc.) biased that viewpoint.
I assume you might mean to ask "why wasn't PyPy adopted in some formal way into CPython" rather than a separate project, for which the answer is at least partially likely to be because it's a completely separate implementation.
By now it should be clear to anybody working on Python JIT that the probability of failure is 90%.
The future is probably rewriting performance critical Python code in Rust instead of trying to fix Python.
Or maybe a future LLM could add a JIT to Python in an effort-run.
If I were a contributor I would read such language as saying "we have no respect for you or your intelligence, so we'll just straight up gaslight you and expect you to accept it."
The dictum can't be read literally - it has to be read like the manipulative, narcissist-speak that it is. And what it's telling you is - get out.
out of curiosity, why not?
I mean it seems like they want to get a full spec of what JIT should look like in main? given the faff that hapened with the GC removal, I can sort see why they'd want to do this properly. Especially now that it seems like its practical.
That's a very strong claim. I'm not seeing that at all. What causes you to interpret it that way?
https://news.ycombinator.com/item?id=48421400
At the time I posted it, both were pretty lacking in attention, so it made sense to direct to the earlier of the two.
I did click on your link, it was a waste of time and that wasn't very nice.