John Fouhy wrote: > On 15/05/06, Kent Johnson <[EMAIL PROTECTED]> wrote: >> You can come pretty close with generators, though it hurts to think >> about what is actually going on behind the scenes here: >> >> In [1]: import itertools >> >> In [2]: def fibs(): >> ...: yield 0 >> ...: yield 1 >> ...: fib1 = fibs() >> ...: fib2 = fibs() >> ...: fib2.next() >> ...: for a, b in itertools.izip(fib1, fib2): >> ...: yield a+b > > Yikes! > > f = fibs() > for i in range(100): > start = time.clock() > x = f.next() > dur = time.clock() - start > print i, x, dur > if dur > 10: > break > > 0 0 2.03936533833e-005 > 1 1 5.5873022968e-006 > 2 1 1.59238115459e-005 > 3 2 1.25714301678e-005 > 4 3 1.95555580388e-005 > 5 5 2.15111138427e-005 > 6 8 2.93333370582e-005 > 7 13 6.06222299203e-005 > 8 21 7.87809623849e-005 > 9 34 0.000119568269152 > 10 55 0.000383568302675 > 11 89 0.000409269893241 > 12 144 0.000650082622233 > 13 233 0.000979454092629 > 14 377 0.00172200656787 > 15 610 0.00713330884232 > 16 987 0.00450979104886 > 17 1597 0.0128720270314 > 18 2584 0.0150373860365 > 19 4181 0.0283779083654 > 20 6765 0.0490199173359 > 21 10946 0.135228918759 > 22 17711 0.240615497221 > 23 28657 0.365666586116 > 24 46368 0.827867508301 > 25 75025 2.14721368219 > 26 121393 4.08266218193 > 27 196418 20.1769099145 > > Hmm, do you know an easy way to check how much memory python is using? > My HDD was swapping like crazy by the end of that..
Does the Haskell version do any better? ISTM this formulation is fundamentally inefficient; calculating fib(n) is going to create something like fib(n-1) fib objects. In the Python case each fib is a generator which I imagine means it has some kind of stack frame associated with it. Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
