Sorry to repost, but does anyone have an idea about what I could do to track down the source of the slowdown? Should I run with some trace to try to compare how different parts behave? How could I do that? Thanks, Laurent. Hi and first of all, thanks for that great project. Now to my "problem". I'm doing some puzzle-solving, constraint processing with Python and on my particular program, PyPy 1.8 showed a 50% increase in running time over PyPy 1.7. I'm not doing anything fancy (no numpy, itertools, etc.). The program is here: https://github.com/slowfrog/hexiom To reproduce: - fetch hexiom2.py and level36.txt from github - run 'pypy hexiom2.py -sfirst level36.txt' On my machine (Windows 7) the timings are the following: Python 2.6.5/Windows 32 3m35s Python 2.7.1 (930f0bc4125a, Nov 27 2011, 11:58:57) [PyPy 1.7.0 with MSC v.1500 32 bit] 31s Python 2.7.2 (0e28b379d8b3, Feb 09 2012, 18:31:47) [PyPy 1.8.0 with MSC v.1500 32 bit] 48s I'm using the default options. Do you have any idea what could be causing that? Thanks, Laurent.