how to measure running time of algorithms in python

Question

Possible Duplicates    Accurate timing of functions in python   accurately measure time python function takes       How can i mesure and compare the running times of my algorithms written in python  Also point me to a nice algorithms site forum like stackoverflow if you can

User · Accepted Answer

I am not 100  sure what is meant by  running times of my algorithms written in python   so I thought I might try to offer a broader look at some of the potential answers    Algorithms don t have running times  implementations can be timed  but an algorithm is an abstract approach to doing something  The most common and often the most valuable part of optimizing a program is analyzing the algorithm  usually using asymptotic analysis and computing the big O complexity in time  space  disk use and so forth   A computer cannot really do this step for you  This requires doing the math to figure out how something works  Optimizing this side of things is the main component to having scalable performance  You can time your specific implementation  The nicest way to do this in Python is to use timeit  The way it seems most to want to be used is to make a module with a function encapsulating what you want to call and call it from the command line with python -m timeit       Using timeit to compare multiple snippets when doing microoptimization  but often isn t the correct tool you want for comparing two different algorithms  It is common that what you want is asymptotic analysis  but it s possible you want more complicated types of analysis  You have to know what to time  Most snippets aren t worth improving  You need to make changes where they actually count  especially when you re doing micro-optimisation and not improving the asymptotic complexity of your algorithm    If you quadruple the speed of a function in which your code spends 1  of the time  that s not a real speedup  If you make a 20  speed increase on a function in which your program spends 50  of the time  you have a real gain   To determine the time spent by a real Python program  use the stdlib profiling utilities  This will tell you where in an example program your code is spending its time

User · Answer

The programming language doesn t matter  measuring the runtime complexity of an algorithm works the same way regardless of the language  Analysis of Algorithms by Stanford on Google Code University is a very good resource for teaching yourself how to analyze the runtime complexity of algorithms and code    If all you want to do is measure the elapsed time that a function or section of code took to run in Python  then you can use the timeit or time modules  depending on how long the code needs to run

User · Answer

Using a decorator for measuring execution time for functions can be handy  There is an example at http   www zopyx com blog a-python-decorator-for-measuring-the-execution-time-of-methods   Below I ve shamelessly pasted the code from the site mentioned above so that the example exists at SO in case the site is wiped off the net   import time                                                  def timeit method        def timed  args    kw           ts   time time           result   method  args    kw          te   time time            print   r   r   r   2 2f sec                     method   name    args  kw  te-ts          return result      return timed  class Foo object         timeit     def foo self  a 2  b 3           time sleep 0 2    timeit def f1        time sleep 1      print  f1    timeit def f2 a       time sleep 2      print  f2  a   timeit def f3 a   args    kw       time sleep 0 3      print  f3   args  kw  f1   f2 42  f3 42  43  foo 2  Foo   foo        John

User · Answer

For small algorithms you can use the module timeit from python documentation   def test         Stupid test function      L          for i in range 100           L append i   if   name       main         from timeit import Timer     t   Timer  test      from   main   import test       print t timeit     Less accurately but still valid you can use module time like this   from time import time t0   time   call mifuntion vers 1   t1   time   call mifunction vers 2   t2   time    print  function vers1 takes  f    t1-t0  print  function vers2 takes  f    t2-t1

User · Answer

The module timeit is useful for this and is included in the standard Python distribution   Example   import timeit timeit Timer  for i in xrange 10   oct i    timeit

[python] how to measure running time of algorithms in python

Examples related to python

Examples related to algorithm