New subject: Different cpu python code usage between embedded mode and standalone mode

7 Jun 2008

      Hi list,

First Hello to all, I have a serious problem for understand some results
when I'm comparing cpu usages between same python code in embedded mode and
standalone mode ( python name_script.py )

This last months I have been writing a  program in c like to mod_python for
embedding python language, it's a middleware for dispatch and execute python
batch programs into several nodes. Now I'm writing some python program for
test how scale this into several nodes and comparing with "standalone"
performance.

I found a very strange problem with one application named md5challenge, this
aplication try to calculate the max number md5 digest in several seconds,
md5challenge use a simple signal alarm for stop program when time has
passed. This is the code of python script

_nrdigest = 0
_const_b = 20
_f = None
_signal = False

def handler_alrm(signum, frame):
    global _signal
    global _nrdigest
    global _f

    _signal = True

def try_me():
    global _nrdigest
    global _f
    global _signal

    _f = open("/dev/urandom","r")
    while _signal is not True:
        buff = _f.read(_const_b)
        md5.md5(buff).hexdigest()
        _nrdigest = _nrdigest + 1

    if _f is not None :
        _f.close()

# Define entry point with one input variable
# req is a instance of Request object, usefull members of this object are:
# req.input is a dictionary with input.xml variables
# req.constants is a dictionary with constants defined into signature.xml
# req.output is void dictionary for full with output variables
# req.config is a dictionary with config values take from namespace
# req.apdn_pid is a pid of aplication

def main( req ):
    global _nrdigest

    signal.signal(signal.SIGALRM, handler_alrm)
    signal.alarm(req.input['time'])

    try_me()

    req.output['count'] = _nrdigest

    return req.OK

if __name__ == "__main__":

    # test code
    class test_req:
        pass

    req = test_req()
    req.input = { 'time' : 10 }
    req.output = { 'ret' : 0, 'count' : 0 }
    req.OK = 1

    main(req)

    print "Reached %d digests" % req.output['count']

When I try to run this program in standalone into my Pentium Dual Core
md5challenge reached 1.000.000 milion keys in 10 seconds but when i try to
run this code in embedded mode md5challenge reached about 200.000 more keys
!!! I repeat this test many times and  always  wins  embedded mode  !!!
What's happen ?

Also I tested to erase read dependencies from /dev/random, and calculate all
keys from same buffer. In this case embedded mode win always also, and the
difference are more bigger !!!

The alarm time expires in both case in 10 seconds.

Thks to all, can anybody help to me for understand this results ?

-- 
Pau Freixes
Linux GNU/User

Different cpu python code usage between embedded mode and standalone mode

Pau Freixes

Guido van Rossum

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