Martin v. Löwis wrote: > Felipe Almeida Lessa wrote: > > I love benchmarks, so as I was testing the options, I saw something very > > strange: > > > > $ python2.4 -mtimeit 'x = range(100000); ' > > 100 loops, best of 3: 6.7 msec per loop > > $ python2.4 -mtimeit 'x = range(100000); del x[:]' > > 100 loops, best of 3: 6.35 msec per loop > > $ python2.4 -mtimeit 'x = range(100000); x[:] = []' > > 100 loops, best of 3: 6.36 msec per loop > > $ python2.4 -mtimeit 'x = range(100000); del x' > > 100 loops, best of 3: 6.46 msec per loop > > > > Why the first benchmark is the slowest? I don't get it... could someone > > test this, too? > > In the first benchmark, you need space for two lists: the old one and > the new one; the other benchmarks you need only a single block of > memory (*). Concluding from here gets difficult - you would have to study > the malloc implementation to find out whether it works better in one > case over the other. Could also be an issue of processor cache: one > may fit into the cache, but the other may not.
Addition to the previous message. Now I follow you :) There are indeed two arrays and cache seems to be the second reason for slowdown, but iterating backwards is also contributing to slowdown. -- http://mail.python.org/mailman/listinfo/python-list
