Trouble with psyco

[Philip Smith]

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)

Phil
"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 
>> <http://www.rcblue.com/Python/spinForWeb.py>
>>
>> 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
>>
>> Thanks,
>
>  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 
> concerned.
>
>  Without psyco, "later" happens very frequently, almost constantly even, 
> and so Control-C generally has an instant effect.
>
>  Hope this helps,
>
>  Jp