Example of the selection of a single individual
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Fitness proportionate selection, also known as roulette wheel selection, is a genetic operator used in genetic algorithms for selecting potentially useful solutions for recombination.

In fitness proportionate selection, as in all selection methods, the fitness function assigns a fitness to possible solutions or chromosomes. This fitness level is used to associate a probability of selection with each individual chromosome. If fi{displaystyle f_{i}} is the fitness of individual i{displaystyle i} in the population, its probability of being selected is

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pi=fiΣj=1Nfj,{displaystyle p_{i}={frac {f_{i}}{Sigma _{j=1}^{N}f_{j}}},}

The Chatroulette website was created by Andrey Ternovskiy, a 17-year-old high-school student in Moscow, Russia. Ternovskiy says the concept arose from video chats he used to have with friends on Skype, and that he wrote the first version of Chatroulette in 'two days and two nights'. Chatroulette is the original internet-breaking random chatroom to meet guys, girls, celebrities, musicians, comics, and all sorts of fascinating people. No login required. The Chatroulette website was created by Andrey Ternovskiy, a 17-year-old high-school student in Moscow, Russia. Ternovskiy says the concept arose from video chats he used to have with friends on Skype, and that he wrote the first version of Chatroulette in 'two days and two nights'.

where N{displaystyle N} is the number of individuals in the population.

This could be imagined similar to a Roulette wheel in a casino. Usually a proportion of the wheel is assigned to each of the possible selections based on their fitness value. This could be achieved by dividing the fitness of a selection by the total fitness of all the selections, thereby normalizing them to 1. Then a random selection is made similar to how the roulette wheel is rotated.

While candidate solutions with a higher fitness will be less likely to be eliminated, there is still a chance that they may be eliminated because their probability of selection is less than 1 (or 100%). Contrast this with a less sophisticated selection algorithm, such as truncation selection, which will eliminate a fixed percentage of the weakest candidates. With fitness proportionate selection there is a chance some weaker solutions may survive the selection process. This is because even though the probability that the weaker solutions will survive is low, it is not zero which means it is still possible they will survive; this is an advantage, because there is a chance that even weak solutions may have some features or characteristics which could prove useful following the recombination process.

The analogy to a roulette wheel can be envisaged by imagining a roulette wheel in which each candidate solution represents a pocket on the wheel; the size of the pockets are proportionate to the probability of selection of the solution.[citation needed] Selecting N chromosomes from the population is equivalent to playing N games on the roulette wheel, as each candidate is drawn independently.

Other selection techniques, such as stochastic universal sampling[1] or tournament selection, are often used in practice. This is because they have less stochastic noise, or are fast, easy to implement and have a constant selection pressure.[2]

The naive implementation is carried out by first generating the cumulative probability distribution (CDF) over the list of individuals using a probability proportional to the fitness of the individual. A uniform random number from the range [0,1) is chosen and the inverse of the CDF for that number gives an individual. This corresponds to the roulette ball falling in the bin of an individual with a probability proportional to its width. The 'bin' corresponding to the inverse of the uniform random number can be found most quickly by using a binary search over the elements of the CDF. It takes in the O(log n) time to choose an individual. A faster alternative that generates individuals in O(1) time will be to use the alias method.

Recently, a very simple algorithm was introduced that is based on 'stochastic acceptance'.[3] The algorithm randomly selects an individual (say i{displaystyle i}) and accepts the selection with probability fi/fM{displaystyle f_{i}/f_{M}}, where fM{displaystyle f_{M}} is the maximum fitness in the population. Certain analysis indicates that the stochastic acceptance version has a considerably better performance than versions based on linear or binary search, especially in applications where fitness values might change during the run.[4] While the behavior of this algorithm is typically fast, some fitness distributions (such as exponential distributions) may require O(n){displaystyle O(n)} iterations in the worst case. This algorithm also requires more random numbers than binary search.

Pseudocode[edit]

For example, if you have a population with fitnesses [1, 2, 3, 4], then the sum is (1 + 2 + 3 + 4 = 10). Therefore, you would want the probabilities or chances to be [1/10, 2/10, 3/10, 4/10] or [0.1, 0.2, 0.3, 0.4]. If you were to visually normalize this between 0.0 and 1.0, it would be grouped like below with [red = 1/10, green = 2/10, blue = 3/10, black = 4/10]:

Using the above example numbers, this is how to determine the probabilities:

The last index should always be 1.0 or close to it. Then this is how to randomly select an individual:

See also[edit]

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References[edit]

  1. ^Bäck, Thomas, Evolutionary Algorithms in Theory and Practice (1996), p. 120, Oxford Univ. Press
  2. ^Blickle, Tobias; Thiele, Lothar (1996). 'A Comparison of Selection Schemes Used in Evolutionary Algorithms'. Evolutionary Computation. 4 (4): 361–394. doi:10.1162/evco.1996.4.4.361. ISSN1063-6560. S2CID42718510.
  3. ^A. Lipowski, Roulette-wheel selection via stochastic acceptance (arXiv:1109.3627)[1]
  4. ^Fast Proportional Selection

External links[edit]

  • C implementation (.tar.gz; see selector.cxx) WBL
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Fitness_proportionate_selection&oldid=979505220'
Chatroulette
Online chat, voice chat, video chat
Available inEnglish
OwnerAndrey Ternovskiy
Created byAndrey Ternovskiy
CEOAndrew William Done
RevenuePremium
URLwww.chatroulette.com
CommercialNo
RegistrationNot Required
LaunchedNovember 16, 2009; 11 years ago[1]
Current statusActive

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Chatroulette is an online chatwebsite that pairs random users for webcam-based conversations. Visitors to the website begin an online chat (text, audio, and video) with another visitor. At any point, either user may leave the current chat by initiating another random connection.[2][3] According to The New York Times, the site is intensely addictive.[4] In February 2010, a few months after the website was created,[5] about 35,000 people were on Chatroulette at any given time. Around the beginning of March, creator Andrey Ternovskiy estimated the site to have around 1.5 million users.[6] According to a survey carried out by RJMetrics, about one in eight spins on Chatroulette yielded 'R-rated' content.[7] Parody shows such as The Daily Show and South Park have lampooned this aspect of the service, and nudity has become an established part of the site's notoriety.[8] In spring 2020, Ternovskiy appointed Andrew William Done, Australian tech entrepreneur, as the CEO of Chatroulette.[9] Done has previously founded companies like Simple Machines in Sydney, Australia, and operated as CTO for multiple tech start ups, such as Goodlord in London.[10] Following product changes in spring 2020, and enhanced by the COVID-19 Pandemic, Chatroulette's user numbers have more than doubled between 2019 and 2020.[10] Due to a big relaunch of Chatroulette in June 2020, including new features and a more reliable and modern platform, user numbers are expected to continuously grow.[9]

Overview[edit]

The Chatroulette website was created by Andrey Ternovskiy, a 17-year-old high-school student in Moscow, Russia.[11] Ternovskiy says the concept arose from video chats he used to have with friends on Skype, and that he wrote the first version of Chatroulette in 'two days and two nights'.[6] Ternovskiy chose the name 'Chatroulette' after watching The Deer Hunter, a 1978 film set in the Vietnam War in which prisoners of war are forced to play Russian roulette.[12] The site pairs its users at random, and allows them to type messages to one another while watching the other user's webcam.[citation needed]

Ternovskiy built the site on an old computer he had in his bedroom. The site initially had 20 users, and then it doubled daily for a period, according to Ternovskiy in 2010.[13] He discusses that he did not advertise or post his site anywhere; in fact, people starting talking about the website and knowledge of it gradually spread by word of mouth. As the number of active users grew, Ternovskiy has had to rewrite the entire code to cope with the load, the management of which being the most challenging part of his project. Despite the expansion of the service, he still codes everything on his own. Ternovskiy sought help from his longtime friend Vlad Kostanyan, who helped him with his side projects.[14]

In early November 2009, shortly after the site launched, it had 500 visitors per day.[6] One month later there were 50,000.[6] The site has been featured in The New York Times,[11]The New Yorker,[15]New York magazine,[16] and on Good Morning America,[17]Newsnight in the United Kingdom,[18]Tosh.0,[19] and The Daily Show with Jon Stewart.[20] In February 2010, about 35,000 people were on Chatroulette at any given time.[21] Around the beginning of March, Ternovskiy estimated the site to have around 1.5 million users, around 33% of them from the United States and 5% from Germany.[6]

An early growth phase was funded by a $10,000 investment from Ternovskiy's parents, which he soon paid back.[6] As of March 2010, Ternovskiy was running the site from his childhood bedroom, assisted by four programmers who were working remotely, and the site was supported through advertising links to an online dating service.[6] The site uses several high-end servers all located in Frankfurt, Germany.[22]

In June 2010 Andrey was awarded by Webby for excellence on the Internet [23]

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According to New York Times, the site is intensely addictive.[4] One informal study published in March 2010 showed that nearly half of all Chatroulette 'spins' connected a user with someone in the US, while the next most likely country was France with 15%. On average, in sessions showing a single person 89% of these were male and 11% were female; 8% of spins showed multiple people behind the camera. About one in three females appeared as such a group, and one in 12 males. A user was more likely to encounter a webcam featuring no person at all than one featuring a sole female. About one in eight spins yielded someone apparently naked, exposing themselves, or engaging in a sexual act. A user was twice as likely to encounter a sign requesting female nudity than to encounter actual female nudity.[7]

The website uses Adobe Flash to display video and access the user's webcam. Flash's peer-to-peer network capabilities (via RTMFP) allow almost all video and audio streams to travel directly between user computers, without using server bandwidth. However, certain combinations of routers will not allow UDP traffic to flow between them, and then falling back to RTMP is necessary.[24]

Initially, the site only asked users to confirm that they are at least 18 years old and agree on terms to not broadcast any offensive or pornographic content. Login or registration was not required. However, the website now requires users to register for free before they can use the features of the website. The signup requires a username, email address, and password. Details such as age, gender, and location can be further added under profile and settings. This tab also allows users to write an 'about me' section about themselves, including languages they speak and their taste in music, movies, and games. Users can also upload an image of themselves to add to their profiles.

Inappropriate content[edit]

Alert message shown after the user has been reported three times
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Within a year of the site's launch, Chatroulette received criticism, particularly with respect to the offensive, obscene, or pornographic material that some users of this site were exhibiting. Psychiatrist Dr. Keith Ablow advised, 'Parents should keep all their children off the site because it's much too dangerous for children. It's a predator's paradise. This is one of the worst faces of the Internet that I've seen. It's disconnecting human relationships rather than connecting them.' Emie Allen, president of the National Center for Missing and Exploited Children, told CBS' The Early Show that the site was the 'last place parents want their kids to be. This is a huge red flag; this is extreme social networking. This is a place kids are going to gravitate to.'[25]

Ternovskiy told the New York Times that 'Everyone finds his own way of using the site. Some think it is a game, others think it is a whole unknown world, others think it is a dating service. I think it's cool that such a concept can be useful for so many people. Although some people are using the site in not very nice ways -- I am really against it.'[25] Early users of the site would frequently encounter users who were naked or masturbating in front of the camera. According to certain reports and a firsthand test, the majority of the site's users are male and overwhelmingly young, and people in their 30s are usually mocked on the site for being too 'old'. Some users dress in costumes to entertain the viewer the site pairs them with, while others play music or host dance parties.[2] In 2011, artists Eva and Franco Mattes presented random Chatroulette users with a staged view of a man who had apparently hanged himself, and recorded the reactions.[26]

According to a survey carried out by RJMetrics, about one in eight of feeds from Chatroulette involved 'R-rated' content.[7] Parody shows such as The Daily Show and South Park have lampooned this aspect of the service, and nudity has become an established part of the site's notoriety.[8] A complicated legal environment surrounds Chatroulette with respect to the sexual activities that occur frequently on the site. These activities may be illegal, but who is liable for such content is uncertain due to the level of anonymity of the users.[2]

Reaction to criticisms[edit]

In response, the website has discouraged under-18s from using the site, and prohibits 'pornographic' behavior. Users who experience harassment or witness illegal, immoral, or pornographic activity may report the offending user. If three users complain about the same participant within five minutes, the user is temporarily banned from the service.[6] In August 2012, Chatroulette removed the Safe Mode feature of the website,[clarification needed] and posted new terms and conditions, stating that nudity was no longer allowed on any part of the site.[27] Chatroulette later changed their terms of use, making it a requirement that all users sign up before using the service.

Early in the site's operation, an algorithm was developed to successfully filter out large quantities of obscene content on Chatroulette, considering that as much as 30% of the 8.5 million monthly unique visitors are under 18 years of age. This has led to a higher proportion of female users accessing the service due to the cleanup.[28] The image recognition algorithms automatically flag users broadcasting sexual content. The filter works in a manner that it identifies excessive amounts of revealed skin while simultaneously recognizes faces as appropriate. A 20,000-user-based sample study proved that the algorithm is able to filter out nearly 60% of the offensive material along with ads on the site.[28] While the video streams are transmitted in a peer-to-peer manner, without passing through the site's server, Chatroulette does periodically take screenshots of the users' video content. Humans then check the screenshots flagged by the algorithms and proceed to block the offending users for a period of time.[28][29] In an interview, Ternovskiy states, 'While recognition software improves, we have employed a moderation team to review pictures manually. We now have around 100 moderators who are all monitoring all webcam feeds and marking inappropriate ones. The combination of filter technology and moderation results in the banning of 50,000 inappropriate users daily.'[28]

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See also[edit]

References[edit]

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  1. ^'Chatroulette.com WHOIS, DNS, & Domain Info - DomainTools'. WHOIS. Retrieved 2016-11-15.
  2. ^ abcD. Sutter, John (February 24, 2010). 'Chatroulette offers random webcam titillation'. CNN. Retrieved 19 March 2013.
  3. ^Harley, James. 'What is this video chat craze used for?'. Wocchat.com. Wocchat.com. Retrieved 19 October 2015.
  4. ^ abKreps, David. 'Foucault, Exhibitionism and Voyeurism on Chatroulette'(PDF). Murdoch University. Retrieved 20 March 2013.
  5. ^'Whois chatroulette.com'. www.whois.com. Retrieved 2019-01-08.
  6. ^ abcdefghYevgeny Kondakov and Benjamin Bidder: 17-Year-Old Chatroulette Founder: 'Mom, Dad, the Site Is Expanding' Interview with Andrey Ternovskiy, Der Spiegel, 5 March 2010
  7. ^ abcMoore, Robert J. (2010-03-16). 'Chatroulette Is 89 Percent Male, 47 Percent American, And 13 Percent Perverts'. TechCrunch. Retrieved 2010-05-14.
  8. ^ abSouth Park Takes on Tron, Facebook, and Chat Roulette from MovieViral.com
  9. ^ ab'«Herr Done, warum sehe ich hier so viele Penisse?»'. www.20min.ch (in German). 2020-04-11. Retrieved 2020-06-12.
  10. ^ abWirtschaft, Finanz und. 'Kaffee mit...'Finanz und Wirtschaft (in German). Retrieved 2020-06-26.
  11. ^ abStone, Brad (2010-02-13). 'Chatroulette's Creator, 17, Introduces Himself - Bits Blog - NYTimes.com'. Bits.blogs.nytimes.com. Retrieved 2010-02-28.
  12. ^Nick Bilton: One on One: Andrey Ternovskiy, Creator of Chatroulette (interview) Bits Blog, The New York Times online, March 12, 2010
  13. ^Bilton, Nick (March 12, 2010). 'One on One: Andrey Ternovskiy, Creator of Chatroulette'. New York Times. Retrieved 19 March 2013.
  14. ^'Chatroulette'.
  15. ^Ioffe, Julia (17 May 2010). 'Roulette Russian: The teen-ager behind Chatroulette'. The New Yorker. Retrieved 24 November 2014.
  16. ^Anderson, Sam (2010-02-05). 'Is ChatRoulette the Future of the Internet or Its Distant Past? - New York Magazine'. Nymag.com. Retrieved 2010-02-28.
  17. ^'Chatroulette: Talking to Strangers on Internet - ABC News'. Abcnews.go.com. Retrieved 2010-02-28.
  18. ^'Newsnight: From the web team: Tuesday 9 March 2010'. BBC. 2010-03-09. Retrieved 2010-05-14.
  19. ^'Chat Roulette Tosh.0'. Comedy Central. Retrieved 2010-05-14.
  20. ^'Tech-Talch - Jon encounters several reporters and naked masturbating men as he explores Chatroulette'. www.thedailyshow.com/. Retrieved 2010-03-05.
  21. ^John D. Sutter, CNN (2010-02-24). 'Chatroulette offers random webcam titillation - CNN.com'. Edition.cnn.com. Retrieved 2010-02-28.
  22. ^'Online Review Reveals Today's Top Five Video Chat Sites'. PR Newswire. Retrieved 19 March 2013.
  23. ^'Chatroulette Special Archievment'. Webby.
  24. ^'Stratus Discussion Group'. 2010-04-08. Retrieved 2010-04-08.
  25. ^ abRhett Miller, Joshua (March 1, 2010). 'Chatroulette Is 'Predator's Paradise,' Experts Say'. Fox News. Retrieved 20 March 2013.
  26. ^Westcott, James (2011-08-18). 'Perform Yourself'. New York Times. Retrieved 2013-04-29.
  27. ^Chatroulette Deletes Safe ModeArchived 2012-08-16 at the Wayback Machine from roulettechatsites.com
  28. ^ abcdBulatovic, Peja (January 20, 2011). 'Nudity filter helps Chatroulette clean up'. CBC. Retrieved 19 March 2013.
  29. ^Xing, Xinyu; et al. (January 2011). 'SafeVchat: Detecting Obscene Content and Misbehaving Users in Online Video Chat Services'. Department of Computer Science, University of Colorado at Boulder. arXiv:1101.3124. Bibcode:2011arXiv1101.3124X.Missing or empty url= (help)

External links[edit]

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