PyPy fireworks
==============

:Authors: Maciej Fijalkowski
:Location: Warsaw Univeristy
:Date: 1.XII.2006

.. raw:: html

   <script src="jssource.js" type="text/javascript"></script>
   <script src="MochiKit.js" type="text/javascript"></script>

What is PyPy?
=============

* An implementation of Python written in Python

* A very flexible compiler toolchain

* An open source project (MIT License)

* A STREP ("Specific Targeted REsearch Project"), partially funded by the EU

* A lot of fun!

Compiler toolchain:
===================

* eats RPython

* C considered harmful

* is kind-of-stable right now

Flow graphs & annotation:
=========================

* We create flow graph out of RPython code `flow`_::

   def g(x):
      return 1

   def f(x):
      return g(x) + 3

* We `annotate`_ variables encountered

* It must be "static-enough" to perform such operation

* We `RType`_ (creating low-level types)

* Source generation

.. _`flow`: javascript:flow()
.. _`annotate`: javascript:annotate()
.. _`RType`: javascript:rtype()

RPython:
========

* *is* Python (can be unittested in Python)

* Can perform full type inference (top to bottom)

* Is run over living python objects (full range of meta-programming)

* Is build "as we need it", so no real definition

Backends & more flow graphs:
============================

* LLtype-based: C, LLVM, 

* OOtype-based: CLI, JVM, JavaScript, (CL and Squeak in some state).

* All optimisations are done on flow graphs

* `example`_, and a `constant-folded one`_::

    def g():
       return 3
        
    def f():
       return g() + 1 * 2

* Wide range of possible things to do with it

.. _`example`: javascript:example()
.. _`constant-folded one`: javascript:const_fold()

JavaScript backend:
===================

* Co-funded by Google Summer of Code *and* Summer of PyPy.

* Mochikit: Makes JavaScript suck less...

JavaScript backend:
===================

* pypy.js: makes JavaScript suck less by not using it::

   def f(x):
      return dom.get_document().getElementById(x)

* Unittest in python run in browser::

   def test_f():
      assert isinstance(f("id"), dom.Element)

* Python semantics (not only syntax)::

   try:
       {'a':3}['b']
   except KeyError:
       # will arrive here

JavaScript example one (console):
=================================

.. raw:: html

   <a href="http://localhost:8001">Here</a>

JavaScript example two (Bub'n'Bros):
====================================

.. raw:: html

   <a href="http://localhost:8080">Here</a>

Transparent proxy:
==================

* Idea - proxied to app-level

* Possible usecase - shallow copy of remote objects::
  
    elem = get_remote("obj") # accessed as a name in globals
                             # remote type is faked here
    getattr(elem, '__str__')() # will access remote object *and* remote type
                               # afterwards
  
* Working simulation on top of greenlets::

    def f(x):
        return x
    
    get_remote(obj).method(f) # will work

Deterministic concurrency:
==========================

* So called "stackless" features

* Available primitives: coroutines, greenlets, tasklets::

   c = channel()

   def f():
      c.send(3)

   def g():
      return c.receive()

   tasklet(f)()
   assert g() == 3

* It provides way of copying stack to heap and backwards

Stackless goodies:
==================

* Very deep recursion

* No deadlock

* No race conditions (in a classic sense)

* Explicit scheduling

* Pickling coroutines

* Cloning coroutines

* All based on graph-transform

Composability:
==============

* So called 'cosets'

* Each 'part' has it's own "parent coroutine"

Things that I didn't talk about:
================================

* Offline partial evaluation

* Prolog interpreter written in RPython

* Security approaches

* Garbage collectors (Boehm, mark&sweep, refcounting)

* GIL

* pylib (support library for pypy)

Developement process:
=====================

* Test driven (few thousand tests)

* Distributed team

* Sprint driven (every 2 months)

Summer of PyPy:
===============

* Open for students

* Proposal based

* We can fund sprint-trip as well as staying costs

* Last call (last two EU-funded sprints)