Friday, March 23, 2012

PyCon: Let's Talk About ????

David Beazley gave the keynote on the second day of PyCon. He decided to talk about PyPy.

PyPy made his code run 34x faster, without changing anything.

In theory, it's easier to add new features to Python using PyPy than cPython.

He's been tinkering with PyPy lately.

IPython Notebook is cool.

Is PyPy's implementation only for evil geniuses?

PyPy scares him because there is a lot of advanced computer science inside.

He doesn't know if you can mess around with PyPy.

It takes a few hours to build PyPy.

It needs more than 4G of RAM.

PyPy translates RPython to C. It generates 10.4 million lines of C code!

PyPy is implemented in RPython, which is a restricted subset of Python.

"RPython is [defined to be] everything that our translation toolchain can accept."

The PyPy docs are hard to read.

4513 .py files, 1.25 million non-blank lines of Python.

translate.py convers RPython code to C.

The PyPy version is faster than the C version of Fibonacci! Although, if you turn on C optimizations, they're similar.

RPython is a restricted subset of Python that they used to implement the Python interpreter.

RPython can talk to C code. It's similar to ctypes.

RPython has static typing via type inference.

RPython has to think of the whole program and do type inferencing.

The implementation will blow your mind. It has "snakes and the souls of Ph.D students on the inside."

PyPy doesn't parse your Python. It uses Python code objects.

PyPy has a Python bytecode interpreter.

PyPy translates itself to C using its own bytecode interpreter.

They have regular Python and RPython in the same modules. They have the same syntax, but different semantics. Sometimes, they add docstrings with "NOT_RPYTHON" in them to keep track of which is which.

Stuff that happens at import time is normal Python. Code reached by the entry function is RPython.

They have a foreign function interface and something that's like autoconf.

They use decorators a lot.

"I still don't know how PyPy works."

"I don't even know how CPython works."

He does know how to use the things that make CPython work (ANSI C, Makefiles, etc.).

PyPy has a different set of tools: RPython, translate.py, metaprogramming, FFI.

Ruby is 3600x slower than Python on message-passing with a CPU-bound thread. They had a more extreme case of the same problem Python 3.3 had.

Ruby has a GIL.

He felt completely beat up and out of his league looking at the PyPy source. (I feel better now.)

Can you tinker with PyPy? He still doesn't know. He recommends that you do it anyway.

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