Author: Christian S. Perone

Genetic Algorithms, News, Science

Meanwhile, at the Hall of Justice!

UPDATE 05/10: there is an article in the Physorg too.

Sometimes we face new applications for EC, but for this I was not expecting, from Eurekalert:

WASHINGTON, Oct. 5 — Criminals are having a harder time hiding their faces, thanks to new software that helps witnesses recreate and recognize suspects using principles borrowed from the fields of optics and genetics.

(…)

His software generates its own faces that progressively evolve to match the witness’ memories. The witness starts with a general description such as “I remember a young white male with dark hair.” Nine different computer-generated faces that roughly fit the description are generated, and the witness identifies the best and worst matches. The software uses the best fit as a template to automatically generate nine new faces with slightly tweaked features, based on what it learned from the rejected faces.

“Over a number of generations, the computer can learn what face you’re looking for,” says Solomon.

Read the full article here.

Python, Time Waste

Beautiful Django

The ugly web is over; the trick is to add a Django middleware to process every HttpResponse (with content-type text/html) of Django using BeautifulSoup. The source-code of the middleware is simple:

from BeautifulSoup import BeautifulSoup

class BeautifulMiddleware(object):
    def process_response(self, request, response):
        if response.status_code == 200:
            if response["content-type"].startswith("text/html"):
                beauty = BeautifulSoup(response.content)
                response.content = beauty.prettify()
        return response

We simple check for HTTP response code 200 and then check for a “text/html” content and use BeautifulSoup to process the response. See an example of what it does:

1) I’d a html in my Django application, very ugly and with missing tags:

imagem

This HTML template will be rendered as showed above by Django without the BeautifulSoup middleware, but with the middleware pluged in the settings of your Django app, it will render that html source:

imagem2

BeautifulSoup has figured out sensible places to put the closing tags of the HTML source and has created a pretty indented structure, automagically =)

It’s very easy and interesting create new django middlewares, examples can be JavaScript obfuscators, compressors, automatic performance analysis of html code to improve the render speed of browser and these sort of things.

News, Science

On the irreversibility of evolution

evo_comic

Today I’ve read about an important work done by a team of evolutionary biologists of the University of Oregon, which reveals an important result about the evolutionary irreversibility. The concept of irreversibility states that the future results of evolution at any point in time must depend on the present state and by the past, showing the determinism of evolution; on the other hand, the evolution reversibility dictates that the natural selection can produce the same forms in any given environment, independent of history.

This question about the irreversibility of evolution has remained unsolved because of the fact that we rarely know what features the ancestors had and what the mechanisms was used to evolve into the actual organisms, but the team of Joe Thornton has solved those issues by studying the problem at the molecular level, resurrecting ancestral proteins (GR1) as they existed long ago and using manipulation to study evolutionary process in two directions: forward and reverse.

The results of the work done by the research team was:

Our observations suggest that history and contingency during glucocorticoid receptor evolution strongly limited the pathways that could be deterministically followed under selection.

(…)

Selection is an extraordinarily powerful evolutionary force; nevertheless, our observations suggest that, because of the complexity of glucocorticoid receptor architecture, low-probability permissive substitutions were required to open some mutational trajectories to exploration under selection, whereas restrictive substitutions closed other potential paths. Under selection, some kind of adaptation will always occur, but the specific adaptive forms that are realized depend on the historical trajectory that precedes them. The conditions that once facilitated evolution of the glucocorticoid receptor’s ancestors were destroyed during the realization of its present form. The past is difficult to recover because it was built on the foundation of its own history, one irrevocably different from that of the present and its many possible futures.

So my friend, that’s the way nature evolve, possible never looking back. But this is a great new step for future works and research on the irreversibility of evolution.

References

[1] http://www.nature.com/nature/journal/v461/n7263/abs/nature08249.html
[2] http://www.uoregon.edu/~joet/PDF/bridgham-thornton-nature2009.pdf
[3] http://sciencenow.sciencemag.org/cgi/content/full/2009/923/1

Genetic Algorithms, Pyevolve, Python

n-queens problem using Pyevolve

Last night I’ve read a post on Reddit written by Matthew Rollings showing a code in Python to solve Eight Queens puzzle using EA. So I decided to implement it in Python again but this time using Pyevolve, here is the code:

from pyevolve import *
from random import shuffle

BOARD_SIZE = 64

def queens_eval(genome):
   collisions = 0
   for i in xrange(0, BOARD_SIZE):
      if i not in genome: return 0
   for i in xrange(0, BOARD_SIZE):
      col = False
      for j in xrange(0, BOARD_SIZE):
         if (i != j) and (abs(i-j) == abs(genome[j]-genome[i])):
            col = True
      if col == True: collisions +=1
   return BOARD_SIZE-collisions

def queens_init(genome, **args):
   genome.genomeList = range(0, BOARD_SIZE)
   shuffle(genome.genomeList)

def run_main():
   genome = G1DList.G1DList(BOARD_SIZE)
   genome.setParams(bestrawscore=BOARD_SIZE, rounddecimal=2)
   genome.initializator.set(queens_init)
   genome.mutator.set(Mutators.G1DListMutatorSwap)
   genome.crossover.set(Crossovers.G1DListCrossoverCutCrossfill)
   genome.evaluator.set(queens_eval)

   ga = GSimpleGA.GSimpleGA(genome)
   ga.terminationCriteria.set(GSimpleGA.RawScoreCriteria)
   ga.setMinimax(Consts.minimaxType["maximize"])

   ga.setPopulationSize(100)
   ga.setGenerations(5000)
   ga.setMutationRate(0.02)
   ga.setCrossoverRate(1.0)

   # This DBAdapter is to create graphs later, it'll store statistics in
   # a SQLite db file
   sqlite_adapter = DBAdapters.DBSQLite(identify="queens")
   ga.setDBAdapter(sqlite_adapter)

   ga.evolve(freq_stats=10)

   best = ga.bestIndividual()
   print best
   print "\nBest individual score: %.2f\n" % (best.score,)

if __name__ == "__main__":
   run_main()

It tooks 49 generations to solve a 64×64 (4.096 chess squares) chessboard, here is the output:

Gen. 0 (0.00%): Max/Min/Avg Fitness(Raw) [20.83(27.00)/13.63(7.00)/17.36(17.36)]
Gen. 10 (0.20%): Max/Min/Avg Fitness(Raw) [55.10(50.00)/39.35(43.00)/45.92(45.92)]
Gen. 20 (0.40%): Max/Min/Avg Fitness(Raw) [52.51(55.00)/28.37(24.00)/43.76(43.76)]
Gen. 30 (0.60%): Max/Min/Avg Fitness(Raw) [67.45(62.00)/51.92(54.00)/56.21(56.21)]
Gen. 40 (0.80%): Max/Min/Avg Fitness(Raw) [65.50(62.00)/19.89(31.00)/54.58(54.58)]

        Evolution stopped by Termination Criteria function !

Gen. 49 (0.98%): Max/Min/Avg Fitness(Raw) [69.67(64.00)/54.03(56.00)/58.06(58.06)]
Total time elapsed: 39.141 seconds.

And here is the plots generated by the Graph Plot Tool of Pyevolve:

fig1

fig3

fig5

fig8

Python, Time Waste

Word is smart, but OpenOffice is wise

UPDATE 19/09: it seems that some people had misunderstood the post title, so here is a clarification: I’m not comparing Word with OpenOffice or something like that, the title refers to the design choices of OpenOffice in using Python 2.6 as an option for scripting language, it’s a humorous title and should not be considered in literal sense.

This is a very simple, but powerful, Python script to call Google Sets API (in fact it’s not an API call – since Google doesn’t have an official API for Sets service – but an interesting and well done scraper using BeautifulSoup) inside the OpenOffice 3.1.1 Writer… anyway, you can check the video to understand what it really does:

And here is the very complex source-code:

from xgoogle.googlesets import GoogleSets

def growMyLines():
   """ Calls Google Set unofficial API (xgoogle) """
   doc = XSCRIPTCONTEXT.getDocument()
   controller = doc.getCurrentController()
   selection = controller.getSelection()
   count = selection.getCount();
   text_range = selection.getByIndex(0);
   lines_list = text_range.getString().split("\n");
   gset = GoogleSets(lines_list)
   gset_results = gset.get_results()
   results_concat = "\n".join(gset_results)
   text_range.setString(results_concat);

g_exportedScripts = growMyLines,

You need to put the “xgoogle” module inside the “OpenOffice.org 3\Basis\program\python-core-2.6.1\lib” path, and the above script inside “OpenOffice.org 3\Basis\share\Scripts\python”.

I hope you enjoyed =) with new Python 2.6 core in OpenOffice 3, they have increased the productivity potential at the limit.

Python

Send Subversion commit messages to Twitter

Hello, this is a bridge between Subversion (svn) and Twitter, the intent of this tool is to update a Twitter account when new commit messages arrives in a Subversion repository. We almost never have access to svn repository to add a post-commit hook in a way to call our script and send updates to twitter, so this tool was done to overcome that situation. Using it, you can monitor for example a svn repository from Google Hosting, from Sourceforge.net, etc…

The process of the tool is simple: it will firstly check Twitter account for the last svn commit message (the messages always start with a “$” prefix, or with another user-defined prefix), and then it will check the svn repository server to verify if it has new commits compared to the last tweet revision, if it has, it will update twitter with newer commit messages.

Here is a simple example of a Twitter account updated with commit messages:

twittsvn

The tool is very simple to use in command-line:

Python twittsvn v.0.1
By Christian S. Perone
https://blog.christianperone.com

Usage: twittsvn.py [options]

Options:
  -h, --help            show this help message and exit

  Twitter Options:
    Twitter Accounting Options

    -u TWITTER_USERNAME, --username=TWITTER_USERNAME
                        Twitter username (required).
    -p TWITTER_PASSWORD, --password=TWITTER_PASSWORD
                        Twitter password (required).
    -r TWITTER_REPONAME, --reponame=TWITTER_REPONAME
                        Repository name (required).
    -c TWITTER_COUNT, --twittercount=TWITTER_COUNT
                        How many tweets to fetch from Twitter, default is
                        '30'.

  Subversion Options:
    Subversion Options

    -s SVN_PATH, --spath=SVN_PATH
                        Subversion path, default is '.'.
    -n SVN_NUMLOG, --numlog=SVN_NUMLOG
                        Number of SVN logs to get, default is '5'.

And here is a simple example:

# python twittsvn.py -u twitter_username -p twitter_password \
-r any_repository_name

You must execute it in a repository directory (not the server, your local files) or use the “-s” option to specify the path of your local repository. You should put this script to execute periodicaly using cron or something like that.

To use the tool, you must install pysvn and python-twitter. To install Python-twitter you can use “easy_install python-twitter”, but for pysvn you must check the download section at the project site.

Here is the source-code of the twittsvn.py:

# python-twittsvn - A SVN/Twitter bridge
# Copyright (C) 2009  Christian S. Perone
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see .

import sys
import re
import time
from optparse import OptionParser, OptionGroup

__version__ = "0.1"
__author__  = "Christian S. Perone "

TWITTER_PREFIX = "$"
TWITTER_MSG    = TWITTER_PREFIX + "[%s] Rev. %d by [%s] %s: %s"

try:
   import pysvn
except ImportError:
   raise ImportError, "pysvn not found, check http://pysvn.tigris.org/project_downloads.html"

try:
   import twitter
except ImportError:
   raise ImportError, "python-twitter not found, check http://code.google.com/p/python-twitter"

def ssl_server_trust_prompt(trust_dict):
    return True, 5, True

def run_main():
   parser = OptionParser()
   print "Python twittsvn v.%s\nBy %s" % (__version__, __author__)
   print "https://blog.christianperone.com\n"

   group_twitter = OptionGroup(parser, "Twitter Options",
                       "Twitter Accounting Options")
   group_twitter.add_option("-u", "--username", dest="twitter_username",
                            help="Twitter username (required).",
                            type="string")
   group_twitter.add_option("-p", "--password", dest="twitter_password",
                            help="Twitter password (required).",
                            type="string")
   group_twitter.add_option("-r", "--reponame", dest="twitter_reponame",
                            help="Repository name (required).",
                            type="string")
   group_twitter.add_option("-c", "--twittercount", dest="twitter_count",
                            help="How many tweets to fetch from Twitter, default is '30'.",
                            type="int", default=30)
   parser.add_option_group(group_twitter)

   group_svn = OptionGroup(parser, "Subversion Options",
                       "Subversion Options")
   group_svn.add_option("-s", "--spath", dest="svn_path",
                        help="Subversion path, default is '.'.",
                        default=".", type="string")
   group_svn.add_option("-n", "--numlog", dest="svn_numlog",
                        help="Number of SVN logs to get, default is '5'.",
                        default=5, type="int")
   parser.add_option_group(group_svn)

   (options, args) = parser.parse_args()   

   if options.twitter_username is None:
      parser.print_help()
      print "\nError: you must specify a Twitter username !"
      return

   if options.twitter_password is None:
      parser.print_help()
      print "\nError: you must specify a Twitter password !"
      return

   if options.twitter_reponame is None:
      parser.print_help()
      print "\nError: you must specify any repository name !"
      return

   twitter_api = twitter.Api(username=options.twitter_username,
                             password=options.twitter_password)
   twitter_api.SetCache(None) # Dammit cache !
   svn_api     = pysvn.Client()

   svn_api.callback_ssl_server_trust_prompt = ssl_server_trust_prompt

   print "Checking Twitter synchronization..."
   status_list = twitter_api.GetUserTimeline(options.twitter_username,
                                             count=options.twitter_count)
   print "Got %d statuses to check..." % len(status_list)

   last_twitter_commit = None
   for status in status_list:
      if status.text.startswith(TWITTER_PREFIX):
         print "SVN Commit messages found !"
         last_twitter_commit = status
         break     

   print "Checking SVN logs for ['%s']..." % options.svn_path
   log_list = svn_api.log(options.svn_path, limit=options.svn_numlog)

   if last_twitter_commit is None:
      print "No twitter SVN commit messages found, posting last %d svn commit messages..." % options.svn_numlog
      log_list.reverse()

      for log in log_list:
         message = log["message"].strip()
         date    = time.ctime(log["date"])
         if len(message) <= 0: message = "(no message)"
         twitter_api.PostUpdate(TWITTER_MSG % (options.twitter_reponame,
                                               log["revision"].number,
                                               log["author"], date, message))
      print "Posted %d svn commit messages to twitter !" % len(log_list)
   else:
      print "SVN commit messages found in twitter, checking last revision message...."
      msg_regex        = re.compile(r'Rev\. (\d+) by')
      last_rev_twitter = int(msg_regex.findall(last_twitter_commit.text)[0])

      print "Last revision detected in twitter is #%d, checking for new svn commit messages..." % last_rev_twitter
      rev_num = pysvn.Revision(pysvn.opt_revision_kind.number, last_rev_twitter+1)

      try:
         log_list = svn_api.log(options.svn_path, revision_end=rev_num,
                                limit=options.svn_numlog)
      except pysvn.ClientError:
         print "No more revisions found !"
         log_list = []

      if len(log_list) <= 0:
         print "No new SVN commit messages found !"
         print "Updated !"
         return

      log_list.reverse()

      print "Posting new messages to twitter..."
      posted_new = 0
      for log in log_list:
         message = log["message"].strip()
         date    = time.ctime(log["date"])
         if len(message) <= 0:             
            message = "(no message)"
            if log["revision"].number > last_rev_twitter:
            twitter_api.PostUpdate(TWITTER_MSG % (options.twitter_reponame,
                                                  log["revision"].number,
                                                  log["author"], date, message ))
            posted_new+=1
      print "Posted new %d messages to twitter !" % posted_new
      print "Updated!"

if __name__ == "__main__":
   run_main()
News, Python, Science

An analysis of Benford’s law applied to Twitter

Benford’s law is one of those very weird things that we can’t explain, and when we discover more and more phenomena that obey the law, we became astonished. Two people (Simon Newcomb – 1881 and Frank Benford – 1938) noted the law in the same way, while flipping pages of a logarithmic table book; they noticed that the pages at the beginning of the book were dirtier than the pages at the end.

Currently, there are no a priori criteria that say to us when a dataset will or will not obey the Benford’s Law. And it is because of this, that I’ve done an analysis on the Twitter Public Timeline.

The Twitter API to get Public Timeline is simply useless for this analysis because in the API Docs, they say that the Public Timeline is cached for 60 seconds ! 60 seconds is an eternity, and there is a request rating of 150 request/hour. So, it doesn’t help, buuuuuut, there is an alpha testing API with pretty and very useful streams of data from the Public Timeline; there are many methods in the Twitter Streaming API, and the most interesting one is the “Firehose”, which returns ALL the public statuses, but this method is only available for intere$ting people, and I’m not one of them. Buuuut, we have “Spritzer”, which returns a portion of all public statuses, since it’s only what we have available in the moment, it MUST be useful, and it’s a pretty stream of data =)

So, I’ve got the Spritzer real-time stream of data and processed each new status which arrived with a regex to find all the numbers in the status; if the status was “I have 5 dogs and 3 cats”, the numbers collected should be “[5, 3]”. All those accumulated numbers were then checked against the Benford’s Law. I’ve used Matplotlib to plot the two curves (the Benford’s Law and the Twitter statuses digits distribution) to empirically observe the correlation between them. You can note in the upper right corner of the video, the Pearson’s correlation between the two distributions too.

Here is the video (I’ve seen only after creating of the video, but the color of  the curves are the inverse as seen in the legend):

The video represents the 15 minutes (3.160 captured statuses) of the Twitter Public Timeline. At the end of the video, you can see a Pearson’s correlation of 0.95. It seems that we have found another Benford’s son =)

The little tool to handle the Twitter Spritzer stream of data and plot the correlation graph in real-time was entirely written in Python, I’ll do a clean-up and post it here soon I got time. The tool has generated 1823 png images that were merged using ffmpeg.

I hope you enjoyed =)

Cite this article as: Christian S. Perone, "An analysis of Benford’s law applied to Twitter," in Terra Incognita, 11/08/2009, https://blog.christianperone.com/2009/08/an-analysis-of-benfords-law-applied-to-twitter/.

UPDATE 11/08: the user “poobare” has cited an interesting paper about Benford’s Law on Reddit, here is the link.

More posts about Benford’s Law

Prime Numbers and the Benford’s Law

Delicious.com, checking user numbers against Benford’s Law

Benford’s Law meets Python and Apple Stock Prices