Dear Mikael, dear Carl,
On May 20, 6:55 pm, Carl Witty <[EMAIL PROTECTED]> wrote:
> In this last case, presumably the C compiler has removed the loop
> altogether
... hence, a better example is the following:
def Pyloop(n):
x=0
for i in range(n):
x = x+i
return x
and the other functions accordingly.
But the timings are puzzling for me:
sage: timeit('x=Pyloop(10^6)')
5 loops, best of 3: 91.4 ms per loop
sage: timeit('x=FakeCyloop(10^6)')
5 loops, best of 3: 40.2 ms per loop
sage: timeit('x=Cyloop(10^6)')
5 loops, best of 3: 42.1 ms per loop
sage: timeit('x=FullCyloop(10^6)') # defining x as long
625 loops, best of 3: 1.38 ms per loop
So, although the loop isn't removed by the compiler, x being "long"
improves the time considerably.
Question: Why is FakeCyloop slightly *faster* than Cyloop (here we
have "cdef int i")? I thought that explicitly int-declaring the
running variable in a loop makes it faster?
Yours
Simon
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