Apparent magic number problem

Sat Mar 9 10:16:38 EST 2013

On 09/03/2013 3:51 AM, Peter Otten wrote:
> Colin J. Williams wrote:
>> The program runs correctly under each version, but it runs more slowly
>> under 3.2.
>
>> This is probably due to the fact that the .pyc file is created for the
>> Python 2.7 execution.
>
>> When Python 3.2 is run it fails to create a new .pyc file and if the 2.7
>> .pyc is offered directly a magic number problem is reported.
>
> (1) .pyc files are only created if a module is imported
> (2) The 2.7 .pyc file is put alongside the .py file whereas the 3.2 .pyc is
> put into the __pycache__ subfolder. No clash can occur.
>
> A simple example:
>
> $ ls
> mod.py
> $ cat mod.py
> print("hello world")
>
> Run it; no pyc is created:
>
> $ python2.7 mod.py
> hello world
> $ ls
> mod.py
>
> Import it using 2.7:
>
> $ python2.7 -c 'import mod'
> hello world
> $ ls
> mod.py  mod.pyc
>
> Import it using 3.2:
>
> $ python3.2 -c 'import mod'
> hello world
> $ ls
> mod.py  mod.pyc  __pycache__
> $ ls __pycache__/
> mod.cpython-32.pyc
>
> Run the compiled code:
>
> $ python2.7 mod.pyc
> hello world
> $ python3.2 __pycache__/mod.cpython-32.pyc
> hello world
>
> But I'm with Steven, it's unlikely that the module compilation phase is
> responsible for a noticeable slowdown.
>
>
Thanks to Steven and Peter for their responses.

My main problem appears to be with:

Profile with Python 2.7
        11   25.736    2.340   25.736    2.340 
{numpy.linalg.lapack_lite.dgesv}

Profile with Python 3.2
        11  152.111   13.828  152.111   13.828 {built-in method dgesv}

In other words, the Python 3.2 linear equation solve takes longer than 
with Python 2.7.   I'll pursue this with the numpy folk.

There also appears to be a problem with the generation of the .pyc. 
Please see the example below:

rem temp.bat
dir *.pyc
del *.pyc
C:\python32\python.exe profiler.py Intel P4 2.8GHz 2MB Ram 221 GB Free 
Disk cjw> prof3.txt
dir *.pyc

This is executed with: tmp.bat > tmp.lst

profiler.py contains:
#-------------------------------------------------------------------------------
# Name:        profiler.py
# Purpose:
#
# Author:      cjw
#
# Created:     17/02/2013
# Copyright:   (c) cjw 2013
# Licence:     <your licence>
#-------------------------------------------------------------------------------

import  cProfile as p, pstats as s, sys

def main():
     v= sys.version
     statsFile= 'FPSStats' + v[0] + v[2] + '.txt'
     p.run('import testFPSpeed; testFPSpeed.main()',
                          statsFile)
     t= s.Stats(statsFile)
     t.strip_dirs().sort_stats('cumulative').print_stats(40)

     pass

if __name__ == '__main__':
     main()

tmp.lst contains:

C:\Documents and Settings\cjw.P4A\My Documents\devpy\raspi>rem temp.bat