> There are a number of small built-in functions, such as any, all, and enumerate, that are implemented in C. These functions are an obstacle to optimization as execution flows from Python to C and then back to Python. By rewriting these functions in Python, the optimizer can see across the function call boundary, so they can be better optimized.

Does this mean the experimental JIT could work better with code that uses map/reduce instead of the built-ins any/all? Or does the performance of map and reduce as currently implemented also suffer from this roundtrip between Python and C?