Cython taking more time than regular Python

[Christian Gollwitzer]

Am 20.09.16 um 09:44 schrieb Peter Otten:
> Stefan Behnel wrote:
>
>> Peter Otten schrieb am 19.09.2016 um 14:55:
>>> In [7]: %%cython
>>> def omega(int n):
>>>     cdef long i
>>>     cdef long result = 0
>>>     for i in range(n): result += i
>>>     return result
>>>    ...:
>>>
>>> In [8]: %timeit omega(100000)
>>> 10000 loops, best of 3: 91.6 µs per loop
>>
>> Note that this is the worst benchmark ever. Any non-dump C compiler will
>> happily apply Young Gauß and calculate the result in constant time.
>
> Is that optimization useful in an actual program or just a way to cheat in
> benchmarks?

Good question, but I think this falls under "strength reduction" which 
is a useful optimization of tight loops in C.

However, I'm not convinced it did succeed here. An evaluation of the 
Gauß formula would run in a few *nanoseconds* on any moddern machine. It 
may take a microsecond to call a functino from Python. a hundred 
microseconds means that the loop does run.

	Christian