On Mon, Aug 31, 2009 at 2:20 PM, Antoine Pitrou <solip...@pitrou.net> wrote:
> Gregory P. Smith <greg <at> krypto.org> writes:
> >
> > food for thought as noticed by a coworker who has been profiling some hot
> code
> to optimize a library...If a function does not have a return statement we
> return
> None. Ironically this makes the foo2 function below faster than the bar2
> function at least as measured using bytecode size
>
> I would be surprised if this "bytecode size" difference made a significant
> difference in runtimes, given that function call cost should dwarf the
> cumulated
> cost of POP_TOP and LOAD_CONST (two of the simplest opcodes you could
> find).
>
>
the attached sample code repeatably shows that it makes a difference though
its really not much of one (2-3%).
I was just wondering if a bytecode for a superinstruction of the common
sequence:
6 POP_TOP
7 LOAD_CONST 0 (None)
10 RETURN_VALUE
might be worth it.
#!/usr/bin/python2.4
import dis
import time
def returns_none(x):
x()
def returns_call(x):
return x()
def dummy():
pass
print 'returns_none:'
dis.dis(returns_none)
start, start_clock = time.time(), time.clock()
for _ in xrange(10000000):
returns_none(dummy)
stop, stop_clock = time.time(), time.clock()
print 'elapsed time', stop-start, stop_clock-start_clock
print 'returns_call:'
dis.dis(returns_call)
start, start_clock = time.time(), time.clock()
for _ in xrange(10000000):
returns_call(dummy)
stop, stop_clock = time.time(), time.clock()
print 'elapsed time', stop-start, stop_clock-start_clock
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