Steven D'Aprano, 16.04.2010 12:00:
On Fri, 16 Apr 2010 06:29:40 pm Alan Gauld wrote:
"Stefan Behnel" wrote
import cython
@cython.locals(result=cython.longlong, i=cython.longlong)
def add():
result = 0
for i in xrange(1000000000):
result += i
return result
print add()
[...]
Or is cython doing the precalculation optimisations you mentioned?
And if so when does it do them? Because surely, at some stage, it
still has to crank the numbers?
(We can of course do some fancy math to speed this particular
sum up since the result for any power of ten has a common pattern,
but I wouldn't expect the compiler optimiser to be that clever)
No fancy maths needed, although I'd be amazed (in a good way) to learn
that compiler compiler optimizers recognised this case! Are optimizing
compilers really that clever these days?
If I was writing an optimising C compiler, I'd certainly put this in to
show off in common benchmarks. ;-)
Stefan
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