Editing Gregory Chaitin (section)

==Mathematics and computer science==
Gregory Chaitin is [[Jewish]].  He attended the [[Bronx High School of Science]] and the [[City College of New York]], where he (still in his teens) developed the theory that led to his independent discovery of [[Kolmogorov complexity|algorithmic complexity]].<ref>{{Citation |last1=Li |last2=Vitanyi |title=An Introduction to Kolmogorov Complexity and Its Applications |publisher=Springer |year=1997 |url=https://books.google.com/books?id=LKEmB_GQ53QC |page=92 |quote=G.J.Chaitin had finished the Bronx High School of Science, and was an 18-year-old undergraduate student at City College of the City University of New York, when he submitted two papers.... In his [second] paper, Chaitin puts forward the notion of Kolmogorov complexity.... |isbn=9780387948683 }}</ref><ref>{{Citation |last=Chaitin |first=G. J. |title=On the Length of Programs for Computing Finite Binary Sequences |journal=Journal of the ACM |volume=13 |issue=4 |date=October 1966 |pages=547–569 |doi=10.1145/321356.321363|s2cid=207698337 }}</ref>

Chaitin has defined [[Chaitin's constant]] Ω, a [[real number]] whose digits are [[normal number|equidistributed]] and which is sometimes informally described as an expression of the probability that a random program will halt. Ω has the mathematical property that it is [[Definable number|definable]], with asymptotic approximations from below (but not from above), but not [[computability theory (computation)|computable]].

Chaitin is also the originator of using [[graph coloring]] to do [[register allocation]] in [[compiling]], a process known as [[Chaitin's algorithm]].<ref>G.J. Chaitin, ''Register Allocation and Spilling via Graph Coloring'', [https://patents.google.com/patent/US4571678 US Patent 4,571,678] (1986) [cited from [http://ssw.jku.at/Teaching/PhDTheses/Hoflehner/index.html ''Register Allocation on the Intel® Itanium® Architecture''], p.155]</ref>

He was formerly a researcher at IBM's Thomas J. Watson Research Center in New York. He has written more than 10 books that have been translated to about 15 languages. He is today interested in questions of [[metabiology]] and [[information theory|information-theoretic]] formalizations of the theory of [[evolution]], and is a member of the Institute for Advanced Studies at [[Mohammed VI Polytechnic University]].