Alan Gauld wrote:
"Stefan Behnel" <stefan...@behnel.de> 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()
This runs in less than half a second on my machine, including the
time to launch the CPython interpreter. I doubt that the JVM can even
start up in that time.
I'm astonished at these results. What kind of C are you using. Even in
assembler I'd expect the loop/sum to take at least 3s
on a quad core 3GHz box.
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)
The precalculation optimisations are taking place. If you pass it an
argument to use for the upper limit of the sequence the calculation time
shoots up.
--
Kind Regards,
Christian Witts
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