PyPy - what is it? 
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* a Python Interpreter
* a VM Generator

Python Interpreter
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* single source "specification" in RPython 
* PyPy compiles it to native C, .NET, JVM

RPython: static subset of Python 
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* static subset of Python 
* we do whole-program type-inference

Interpreters written in RPython
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* directly testable on top of CPython 

* GC, threading, **JIT-Compiler** added automatically! 

Garbage Collection framework
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* write GC in RPython
* test in simulation (with pdb!) 
* weave into translation of *any* interpreter

stackless / threading 
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* stackless transform for rpython programs (*any* interpreter)
* infinite recursion, greenlets, co-routines in Python! 

JIT-Compiler Generator 
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* written in RPython
* test in simulation (with pdb!) 
* weave into translation of *any* interpreter

JIT-generator for Python 
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* removes object boxing, frame objects penalties
* but can present them if needed!
* current speedup: 20 times for simple examples 

Any Interpreter or VM? 
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.. image:: mario.png
   :scale: 100
   :align: center

Strong points 
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* large automated test suite, good debugging tools 
* Generating *efficient* Interpreters 
* works for Python, a relatively complex language

Challenges 
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* improve the JIT generator until it can generate a
  good JIT-Compiler for Python! 

* release and distribute Python Interpreter 

* get some more funding