Trouble with psyco
as006d4848 at blueyonder.co.uk
Mon Nov 22 22:53:03 CET 2004
I too am a psyco convert but have found it handles Longs very well.
Interestingly, using a crude factoring algorithm, I tested essentially the
same code in C and Python/Psycho - what took 8 seconds in C (factoring a 30
digit integer) took something like .02 seconds in Python/Psyco. Doesn't
make sense but I shan't complain. The problem I have with psycho is that it
crashes ActivePython - anyone know why? (version 2.3)
"Jp Calderone" <exarkun at divmod.com> wrote in message
news:mailman.6696.1101134159.5135.python-list at python.org...
> On Mon, 22 Nov 2004 02:07:46 -0800, Dick Moores <rdm at rcblue.com> wrote:
>>psyco is acting a bit psycho for me.
>> Please see my spinForWeb.py at
>> When psyco is in use, entering an integer somewhere between 2000 and 2500
>> causes my computer to freeze. Not really freeze but the program doesn't
>> finish, and I have to quit with a ^Q.
>> psyco is really impressive, but I'm disappointed that I can't demonstrate
>> (to friends) counting with it to numbers above 2 billion.
>> If I remark out the "psyco.bind(spin)" line, there's no problem no matter
>> what integer I enter. Can someone explain what the problem with psyco is?
>> Windows XP, Python 2.3.4
> I added a print to your inner loop:
> while k < max:
> k += 1
> if not (k % 1000000L):
> print 'at', k
> Progress is regularly reported, but it is quite, quite slow. So the
> problem is not that psyco is breaking your program. Neither is it
> speeding anything up though, and in fact seems to be slowing it down over
> some sets of data.
> When you cross sys.maxint (a bit above 2 billion, usually), internally
> Python stops storing integers as platform-native data types and switches
> to a data type which can grow almost without bound. Since this new data
> type isn't native to your architecture, every operation on it is vastly
> slower, but Python must switch because the platform-native data type
> cannot take on the values you are asking.
> Python works very hard to make each loop around its evaluator. You're
> asking it to get around quite a few times, doing very little _actual_ work
> each time. This is one of the worst cases for performance in Python.
> With the psyco version, the call to spin() is effectively made into a
> single operation, as far as the interpreter loop is concerned. That's
> part of why it's so much faster - instead of one loop around the
> interpreter per "k += 1", it's just one loop around the interpreter. Big
> difference. But you've discovered one of the costs associated with this -
> Control-C generally sends SIGINT to the process: Python notices this and
> sets a flag which will _later_ cause KeyboardInterrupt to be raised. In
> this case, with psyco enabled, "later" happens when spin() returns,
> because calling spin() was just one operation, as far as Python is
> Without psyco, "later" happens very frequently, almost constantly even,
> and so Control-C generally has an instant effect.
> Hope this helps,
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