Paul Rubin, 05.08.2012 03:38: > Steven D'Aprano writes: >> Runtime optimizations that target the common case, but fall back to >> unoptimized code in the rare cases that the optimization doesn't apply, >> offer the opportunity of big speedups for most code at the cost of >> trivial slowdowns when you do something unusual. > > The problem is you can't always tell if the unusual case is being > exercised without an expensive dynamic check, which in some cases must > be repeated in every iteration of a critical inner loop, even though it > turns out that the program never actually uses the unusual case.
Cython does a lot of optimistic optimisations. That's where a large part of that huge C file comes from that Cython generates from even simple Python code. For example, in CPython, C function calls are so ridiculously faster than Python function calls that it's worth some effort if it saves you from packing an argument tuple to call into a Python function. In fact, we've been thinking about ways to export C signatures from Python function objects, so that code implemented in C (or a C compatible language) can be called directly from other code implemented in C. That's very common in the CPython ecosystem. There are a lot of simple things that quickly add up into a much better performance on average. Stefan -- http://mail.python.org/mailman/listinfo/python-list
