On 20/09/2016 06:27, 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.

Which 'non-dump' C compiler will actually do such an optimisation? (Just so I can steer clear of it; I don't want a compiler wasting /my/ time doing pointless analysis.)

This actually quite a good micro-benchmark precisely because that would be an unusual optimisation.

(With benchmarking you usually want to know how long it takes a program to perform a task, not how long it takes to *not* do it!)


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