Armin Rigo, 08.07.2011 11:18:
Before attacking the problem with the JIT, we should understand better
why PyPy is 4-8 times slower than CPython. Normally you'd expect the
factor to be at most 2. I suppose the answer is that our
itertools.repeat() is bad for some reason.
You shouldn't forget that itertools contains extremely well optimised C
code. I recently tried to (algorithmically) optimise the pure Python
implementations from the CPython docs for Cython, and ended up with timings
between 10% faster and 50% slower. It's actually hard to reach up to the
raw power of hand tuned C code here.
http://blog.behnel.de/index.php?p=163
http://blog.behnel.de/index.php?p=185
Given that some of the functions don't execute anything more than a couple
of assembly instructions per cycle, you'll have to send a really well tuned
high level implementation into the race to even come close. I would expect
that PyPy's implementation simply wasn't written for that.
That being said, it would be nice to have an itertools micro benchmark for
the common Python test suite.
Stefan
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