Editing Claude Shannon (section)

==Other work==
[[File:Shannon and mouse.png|thumb|Shannon and his [[electromechanical]] mouse ''Theseus'' (named after [[Theseus]] from Greek mythology) which he tried to have solve the maze in one of the first experiments in [[artificial intelligence]]]]
[[File:Theseus Maze by Claude Shannon, 1952 - MIT Museum - DSC03702.JPG|thumb|Theseus Maze in MIT Museum]]

===Shannon's mouse===
"Theseus", created in 1950, was a mechanical mouse controlled by an electromechanical relay circuit that enabled it to move around a [[maze|labyrinth]] of 25 squares.<ref name="Bell Labs acknowledgement">{{cite web |title=Bell Labs Advances Intelligent Networks |url=http://www.alcatel-lucent.com/wps/portal/!ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLd4w39w3RL8h2VAQAGOJBYA!!?LMSG_CABINET=Bell_Labs&LMSG_CONTENT_FILE=News_Features/News_Feature_Detail_000025 |url-status=dead |archive-url=https://web.archive.org/web/20120722011711/http://www.alcatel-lucent.com/wps/portal/%21ut/p/kcxml/04_Sj9SPykssy0xPLMnMz0vM0Y_QjzKLd4w39w3RL8h2VAQAGOJBYA%21%21?LMSG_CABINET=Bell_Labs&LMSG_CONTENT_FILE=News_Features%2FNews_Feature_Detail_000025 |archive-date=July 22, 2012}}</ref> The maze configuration was flexible and it could be modified arbitrarily by rearranging movable partitions.<ref name="Bell Labs acknowledgement" /> The mouse was designed to search through the corridors until it found the target. Having travelled through the maze, the mouse could then be placed anywhere it had been before, and because of its prior experience it could go directly to the target. If placed in unfamiliar territory, it was programmed to search until it reached a known location and then it would proceed to the target, adding the new knowledge to its memory and learning new behavior.<ref name="Bell Labs acknowledgement" /> Shannon's mouse appears to have been the first artificial learning device of its kind.<ref name="Bell Labs acknowledgement" />

===Shannon's estimate for the complexity of chess===
{{Main|Shannon number}}
In 1949 Shannon completed a paper (published in March 1950) which estimates the [[Game complexity|game-tree complexity]] of [[chess]], which is approximately 10<sup>120</sup>. This number is now often referred to as the "[[Shannon number]]", and is still regarded today as an accurate estimate of the game's complexity. The number is often cited as one of the barriers to [[Solving chess|solving the game of chess]] using an exhaustive analysis (i.e. [[Brute-force search|brute force analysis]]).<ref name="CS">{{cite journal | author = Claude Shannon | title = Programming a Computer for Playing Chess | journal = Philosophical Magazine | volume = 41 | issue = 314 | year = 1950 | url = http://archive.computerhistory.org/projects/chess/related_materials/text/2-0%20and%202-1.Programming_a_computer_for_playing_chess.shannon/2-0%20and%202-1.Programming_a_computer_for_playing_chess.shannon.062303002.pdf | access-date = January 2, 2018 | archive-url = https://web.archive.org/web/20100706211229/http://archive.computerhistory.org/projects/chess/related_materials/text/2-0%20and%202-1.Programming_a_computer_for_playing_chess.shannon/2-0%20and%202-1.Programming_a_computer_for_playing_chess.shannon.062303002.pdf | archive-date = July 6, 2010 | url-status = dead }}</ref><ref>{{cite AV media|first=James|last=Grime|url=https://www.youtube.com/watch?v=Km024eldY1A|title=How many chess games are possible?|publisher=Numberphile|date=July 24, 2015}}</ref>

===Shannon's computer chess program===
On March 9, 1949, Shannon presented a paper called "Programming a Computer for playing Chess". The paper was presented at the National Institute for Radio Engineers Convention in New York. He described how to program a computer to play chess based on position scoring and move selection. He proposed basic strategies for restricting the number of possibilities to be considered in a game of chess. In March 1950 it was published in ''[[Philosophical Magazine]]'', and is considered one of the first articles published on the topic of programming a computer for playing chess, and using a computer to solve the game.<ref name="CS"/><ref>{{Cite web|url=http://billwall.phpwebhosting.com/articles/computer_early_chess.htm|title=Early Computer Chess Programs by Bill Wall|website=billwall.phpwebhosting.com}}</ref> In 1950, Shannon wrote an article titled "A Chess-Playing Machine",<ref>{{Cite journal |last=Shannon |first=Claude E. |date=1950 |title=A Chess-Playing Machine |url=https://www.jstor.org/stable/24967381 |journal=Scientific American |volume=182 |issue=2 |pages=48–51 |doi=10.1038/scientificamerican0250-48 |jstor=24967381 |pmid=15402252 |bibcode=1950SciAm.182b..48S |issn=0036-8733}}</ref> which was published in ''[[Scientific American]].'' Both papers have had immense influence and laid the foundations for future chess programs.<ref name=":12" /><ref name=":13" />

His process for having the computer decide on which move to make was a [[minimax]] procedure, based on an [[evaluation function]] of a given chess position. Shannon gave a rough example of an evaluation function in which the value of the black position was subtracted from that of the white position. ''Material'' was counted according to the usual [[chess piece relative value]] (1 point for a pawn, 3 points for a knight or bishop, 5 points for a rook, and 9 points for a queen).<ref>{{Citation | title = Artificial Dreams: The Quest for Non-biological Intelligence | author = Hamid Reza Ekbia | year = 2008 | isbn = 978-0-521-87867-8 | page = 46 | publisher = Cambridge University Press }}</ref> He considered some positional factors, subtracting ½ point for each [[doubled pawn]], [[backward pawn]], and [[isolated pawn]]; ''[[mobility (chess)|mobility]]'' was incorporated by adding 0.1 point for each legal move available.

===Shannon's maxim===
Shannon formulated a version of [[Kerckhoffs's principle|Kerckhoffs' principle]] as "The enemy knows the system". In this form it is known as "Shannon's maxim".

===Miscellaneous===
Shannon also contributed to [[combinatorics]] and [[detection theory]].<ref name=":17">{{Cite journal |last1=Effros |first1=Michelle |last2=Poor |first2=H. Vincent |date=2017 |title=Claude Shannon: His Work and Its Legacy |journal=EMS Newsletter |language=en |volume=2017-3 |issue=103 |pages=29–34 |doi=10.4171/NEWS/103/5 |issn=1027-488X|doi-access=free }}</ref> His 1948 paper introduced many tools used in combinatorics. He did work on detection theory in 1944, with his work being one of the earliest expositions of the “matched filter” principle.<ref name=":17" />

He was known as a successful investor who gave lectures on investing. A report from ''[[Barron's]]'' on August 11, 1986, detailed the recent performance of 1,026 mutual funds, and Shannon achieved a higher return than 1,025 of them. Comparing the portfolio of Shannon from the late 1950s to 1986, to [[Warren Buffett]]'s of 1965 to 1995, Shannon had a return of about 28% percent, compared to 27% for Buffett.{{sfn|Poundstone|2005|p=307}} One such method of Shannon's was labeled '''Shannon's demon''', which was to form a portfolio of equal parts cash and a stock, and rebalance regularly to take advantage of the stock's randomly jittering price movements.<ref name=":18">{{Cite book |last1=Benello |first1=Allen C. |url=https://books.google.com/books?id=Wy3fCwAAQBAJ&pg=PA79 |title=Concentrated Investing: Strategies of the World's Greatest Concentrated Value Investors |last2=Biema |first2=Michael van |last3=Carlisle |first3=Tobias E. |date=2016 |publisher=Wiley |isbn=978-1-119-01204-7 |location=Hoboken, New Jersey |pages=79–81 |language=en}}</ref> Shannon reportedly long thought of publishing about investing, but ultimately did not, despite giving multiple lectures.<ref name=":18" /> He was one of the first investors to download stock prices, and a snapshot of his portfolio in 1981 was found to be $582,717.50, translating to $1.5 million in 2015, excluding another one of his stocks.<ref name=":18" />