list.clear() missing?!?

["Martin v. Löwis"]

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.

Regards,
Martin

(*) plus, you also need the integer objects twice.