Question about unreasonable slowness

Łukasz Langa lukasz.langa at gmail.com
Fri Nov 17 16:48:18 CET 2006


allenjo5 at mail.northgrum.com:
> Ok, I built Python 2.5 (same AIX 5.1 machine).  With the "for line in
> shellOut" loop in, it now takes "only" 7 secs instead of the 11 secs in
> python 2.4.3.   So, that's better, but still unreasonably slow.  And to
> answer another's question, I'm using the ksh builtin 'time' command to
> time the overall script.
>
> BTW, I don't think the AIX /bin/sh (actually ksh) is inherently slow.
> This naively translated pure shell version of my python test script
> completes in .1 secs:
>
> i=1
> while ((i<20))
> do ((i+=1))
>    print next
>    print "$shellIn" | /bin/sh -c ':' |
>            while read line
>            do print $line
>            done
> done
>
> Has anyone tried this on a true unix box (AIX, HPUX, Solaris, Linux)?
> It seems to be functioning differently (and faster) on Windows and OS X
>  (though I guess at its heard, OS X is essentially unix).
>
> John.
>   

Linux 2.6.17-1.2142_FC4smp #1 SMP Tue Jul 11 22:57:02 EDT 2006 i686 i686 
i386 GNU/Linux

# <code>

import os
import timeit

def test():
   for i in xrange(20):
       (shellIn, shellOut) = os.popen4("/bin/sh -c ':'")
       print 'next'
       for line in shellOut:
           print line

print timeit.Timer("test()", "from __main__ import test\nimport 
os").timeit(1)

# </code>


This returns in 0.4 seconds. If I time it to do 50 tests, it returns 
after 20.2 - 20.5 seconds. Even if I substitute the for i in xrange() 
construct to your sh-like while statement. And all that through a 
network, with print statements intact. Guess your true Unix box has some 
features unavailable on Fedora Core or MacOS X ;-)

Regards,
Łukasz Langa





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