CSC352 Scripts to Measure Execution Times

Assume that we want to measure the execution time of this program:

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#! /usr/bin/python
# randomTime.py
# D. Thiebaut
import random
import time

time.sleep( random.randrange( 2 ) )

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which takes a random number of time between 0 and 2 seconds.

We use a Python script below that will run the program randomTime.py above the right number of times and keep track of the best time.

Important Note: Depending on whether you are running this script on a Linux box (e.g. beowulf) or on a Mac, you should set the two variables MAC and LINUX accordingly to True or False accordingly.

Setting for a Linux box:

LINUX = True
MAC = False

Setting for a Mac:

LINUX = False
MAC = True

.

#! /usr/bin/python
# timeIt.py
# D. Thiebaut
#
# Note: there are two different version of the command "time".  One is internal
# to bash, the other is located in /usr/bin/time.  Depending on how your path
# is setup, it is possible that when you execute "time" at the command line,
# it is the bash command that runs, but when you execute "time" inside a script,
# (like this python program), it is the /usr/bin/time command that runs.
# Moreover, the output of /usr/bin/time on Linux is not the same as /usr/bin/time
# on Mac OS X.
#
# For this reason, set the MAC and LINUX variables below to True or False
# depending on where you run your program!
#
# on Linux system, the /usr/bin/time command returns a string of the type
#
#    0.01user 0.00system 0:01.08elapsed 1%CPU (0avgtext+0avgdata 0maxresident)k
# 
# on Mac OS X, the /usr/bin/time command returns a string of the type
#
#    0.03 real         0.01 user         0.01 sys
#

from subprocess import Popen, PIPE

MAC=False
LINUX=True
 
def oldRunCommandOnce( program ):
  command="(time  ./%s) 2>&1 | grep real | cut -d'm' -f 2 | cut -d's' -f 1" % program
  p = Popen( command, shell=True, stdin=PIPE, 
                        stdout=PIPE, close_fds=True )
  fin, fout = p.stdin, p.stdout
  execTime = float( fout.readline() )
  return execTime
 
def runCommandOnce( program ):
  if MAC:
    command="(/usr/bin/time  ./%s) 2>&1 | grep real" % program
  elif LINUX:
    command="(/usr/bin/time  ./%s) 2>&1 | grep elapsed" % program
  else:
    print "You must set MAC and LINUX to be True and/or False!"
    return

  p = Popen( command, shell=True, stdin=PIPE,
                        stdout=PIPE, close_fds=True )
  fin, fout = p.stdin, p.stdout
  line = fout.readline()
  if MAC:
    words = line.split()
    execTime = float( words[0] )
    return execTime
  if LINUX:
    #    0.01user 0.00system 0:01.08elapsed 1%CPU (0avgtext+0avgdata 0maxresident)k
    execTime = float( line.split()[0].split( 'u' )[0] )
    return execTime
 
def main():
  bestTime = 1E10
  program  = "randomTime.py"
  for i in range( 3 ):
    execTime = runCommandOnce( program )
    print "sample %d: %f sec" % ( i+1, execTime )
    bestTime = min( bestTime, execTime )
 
  print "Best time = %f sec" % bestTime
 
 
 
main()



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