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Pyjion – A Python JIT Compiler

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Re: Pyjion – A Python JIT Compiler

#71

Post by rowanG077 »

samth wrote: post #63
rowanG077 wrote: post #53

Earlier quoted context omitted.

I see. This doesn't look like a Futaruma Projection to me. What PyPy does is run a python program under their own RPython based interpreter. Then it uses a tracing JIT to JIT the RPython based interpreter. There is no PE going on. No residual specialized program is created. The first Futaruma Projection would be if PyPy would specialize the interpreter based on the python program yielding an executable.

That's exactly what PyPy does do. You get a specialized version of the interpreter which is specialized to the particular program.

No you don't get that. A tracing JIT is not capable of producing an executable like that under normal circumstances. If a certain path is not taken during execution it might not be compiled at all. The point of the first futurama projection is that you get a fully runnable executable that is semantically equivalent to running the original program in the interpreter. A JIT only produces what it sees during execution. I guess it might be possible if you carefully run your program with inputs that exhaust every possible path.

Re: Pyjion – A Python JIT Compiler

#72

Post by haberman »

Python is in a situation where it is enormously popular, due to a winning aesthetic in syntax/ergonomics that appeals to both newbies and experienced programmers. And due to this success, there is a lot of demand and interest in speeding the language up and getting rid of the GIL.

But paradoxically, this veneer of simplicity hides an incredible amount of complexity. You have to read hundreds of lines of CPython to understand the full semantics of a statement like "a + b". The semantics are complicated/compromised by many optimizations and implementation details of CPython. This is a fantastic talk that goes into these details: https://youtu.be/qCGofLIzX6g

It is not good for anybody that the semantics are this quirky. But it's especially not good for people trying to optimize the language, who basically have to implement quirk-for-quirk identical semantics to what CPython has ended up with after 30 years of evolution and optimization.

I wish Python 3.0 had included a more formalized and cleaned up set of semantics. These things can't be simplified without a breaking change to the language (even if only a small number of programs truly depend on these quirks). I would say Python should fix this in 4.0, but the 2->3 transition was so painful and long that I'm not sure the ecosystem can take it.

Re: Pyjion – A Python JIT Compiler

#73

Post by jhgb »

rowanG077 wrote: post #71
samth wrote: post #63

Earlier quoted context omitted.

That's exactly what PyPy does do. You get a specialized version of the interpreter which is specialized to the particular program.

No you don't get that. A tracing JIT is not capable of producing an executable like that under normal circumstances. If a certain path is not taken during execution it might not be compiled at all. The point of the first futurama projection is that you get a fully runnable executable that is semantically equivalent to running the original program in the interpreter. A JIT only produces what it sees during execution.…

Clearly PyPy has to produce executable code if it wants to jump into it. The CPU wouldn't understand if it were asked to jump into something that isn't executable code.

> The point of the first futurama projection

...was to delight viewers with what would turn out to be a wonderful pilot episode?

Re: Pyjion – A Python JIT Compiler

#74

Post by chrisseaton »

haberman wrote: post #72

Python is in a situation where it is enormously popular, due to a winning aesthetic in syntax/ergonomics that appeals to both newbies and experienced programmers. And due to this success, there is a lot of demand and interest in speeding the language up and getting rid of the GIL. But paradoxically, this veneer of simplicity hides an incredible amount of complexity. You have to read hundreds of lines of CPython to un…

It wouldn't be too bad if it was complicated, but explicitly documented and tested.

For example people joke about JavaScript comparison semantics posting things like this https://i.stack.imgur.com/35MpY.png and laughing about it. But I wish Ruby and Python were this explicit and easy to understand!

Re: Pyjion – A Python JIT Compiler

#75

Post by mywittyname »

tgb wrote: post #57
shepardrtc wrote: post #29

Earlier quoted context omitted.

Cython is much easier to implement than people realize. A few import statements and a few types, and then you're good to go. I urge people to give it a try. The speedups can be dramatic.

It certainly is good, but I've never found a great dev setup. It seems like you have to force a full recompile of all cython in the project any time you make a change. At least that was the stated process for the statsmodels library. And it was always a little unclear whether I was running the latest code or hadn't yet actually compiled it.

I've never used cython before. Is it 1-to-1 with standard Python? If so, can you do development using the regular Python binary, and leave the compilation step as a pre-commit operation?

Re: Pyjion – A Python JIT Compiler

#76

Post by marmaduke »

chrisseaton wrote: post #74
haberman wrote: post #72

Python is in a situation where it is enormously popular, due to a winning aesthetic in syntax/ergonomics that appeals to both newbies and experienced programmers. And due to this success, there is a lot of demand and interest in speeding the language up and getting rid of the GIL. But paradoxically, this veneer of simplicity hides an incredible amount of complexity. You have to read hundreds of lines of CPython to un…

It wouldn't be too bad if it was complicated, but explicitly documented and tested. For example people joke about JavaScript comparison semantics posting things like this https://i.stack.imgur.com/35MpY.png and laughing about it. But I wish Ruby and Python were this explicit and easy to understand!

Python docs have pages on the execution model and data model, with notes in implementation details. What more do you want?

https://docs.python.org/3/reference/executionmodel.html

https://docs.python.org/3/reference/datamodel.html

Reading these documents is not hard, and it’s been an enormous help over the years for writing effective efficient Python.

Re: Pyjion – A Python JIT Compiler

#77

Post by marmaduke »

haberman wrote: post #72

Python is in a situation where it is enormously popular, due to a winning aesthetic in syntax/ergonomics that appeals to both newbies and experienced programmers. And due to this success, there is a lot of demand and interest in speeding the language up and getting rid of the GIL. But paradoxically, this veneer of simplicity hides an incredible amount of complexity. You have to read hundreds of lines of CPython to un…

Have you seen the Python docs which have pages on the execution model and data model, with notes in implementation details?

https://docs.python.org/3/reference/executionmodel.html

https://docs.python.org/3/reference/datamodel.html

Re: Pyjion – A Python JIT Compiler

#78

Post by chrisseaton »

marmaduke wrote: post #76
chrisseaton wrote: post #74

Earlier quoted context omitted.

It wouldn't be too bad if it was complicated, but explicitly documented and tested. For example people joke about JavaScript comparison semantics posting things like this https://i.stack.imgur.com/35MpY.png and laughing about it. But I wish Ruby and Python were this explicit and easy to understand!

Python docs have pages on the execution model and data model, with notes in implementation details. What more do you want? https://docs.python.org/3/reference/executionmodel.html https://docs.python.org/3/reference/datamodel.html Reading these documents is not hard, and it’s been an enormous help over the years for writing effective efficient Python.

> What more do you want?

Something formal, so I can actually reason about it and test it.

These documents are just informal prose. Are they sound? I don't know. Do you? Does anyone? Does my implementation match what they say? Who knows. Does CPython even match it? Does anyone know?

Re: Pyjion – A Python JIT Compiler

#79

Post by haberman »

marmaduke wrote: post #77
haberman wrote: post #72

Python is in a situation where it is enormously popular, due to a winning aesthetic in syntax/ergonomics that appeals to both newbies and experienced programmers. And due to this success, there is a lot of demand and interest in speeding the language up and getting rid of the GIL. But paradoxically, this veneer of simplicity hides an incredible amount of complexity. You have to read hundreds of lines of CPython to un…

Have you seen the Python docs which have pages on the execution model and data model, with notes in implementation details? https://docs.python.org/3/reference/executionmodel.html https://docs.python.org/3/reference/datamodel.html

In your second link it says:

> For instance, to evaluate the expression x + y, where x is an instance of a class that has an __add__() method, x.__add__(y) is called.

The talk I linked to (https://youtu.be/qCGofLIzX6g) is a deep dive on how there is much more to the story than the simplified statement above.

What I wish for is not better docs, but rather simpler language in which the statement above would actually be an accurate specification of the behavior implemented by the interpreter.

Re: Pyjion – A Python JIT Compiler

#80

Post by dec0dedab0de »

haberman wrote: post #72

Python is in a situation where it is enormously popular, due to a winning aesthetic in syntax/ergonomics that appeals to both newbies and experienced programmers. And due to this success, there is a lot of demand and interest in speeding the language up and getting rid of the GIL. But paradoxically, this veneer of simplicity hides an incredible amount of complexity. You have to read hundreds of lines of CPython to un…

My gut instinct is that many of Python's quirks are the reason for it's popularity. Though I might not be understanding your suggestion. Could you give a specific example of something you would clean up if you were able to? I have the video in a tab but won't be able to watch until later.
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