I wanted to see how much faster reduce was than using a for loop for simple numerical operations. Here's what I found (using the standard timeit library):
In [54]: print(setup)
from operator import add, iadd
r = range(100)
In [55]: print(stmt1)
c = 0
for i in r:
c+=i
In [56]: timeit(stmt1, setup)
Out[56]: 8.948904991149902
In [58]: print(stmt3)
reduce(add, r)
In [59]: timeit(stmt3, setup)
Out[59]: 13.316915035247803
Looking a little more:
In [68]: timeit("1+2", setup)
Out[68]: 0.04145693778991699
In [69]: timeit("add(1,2)", setup)
Out[69]: 0.22807812690734863
What's going on here? Obviously, reduce does loop faster than for, but the function call seems to dominate. Shouldn't the reduce version run almost entirely in C? Using iadd(c,i) in the for loop version makes it run in ~24 seconds. Why would using operator.add be so much slower than +? I was under the impression + and operator.add run the same C code (I checked to make sure operator.add wasn't just calling + in python or anything).
BTW, just using sum runs in ~2.3 seconds.
In [70]: print(sys.version)
2.7.1 (r271:86882M, Nov 30 2010, 09:39:13)
[GCC 4.0.1 (Apple Inc. build 5494)]
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