Mihalis Yannakakis
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Mihalis Yannakakis (; born 13 September 1953 in
Athens Athens ( ) is the Capital city, capital and List of cities and towns in Greece, largest city of Greece. A significant coastal urban area in the Mediterranean, Athens is also the capital of the Attica (region), Attica region and is the southe ...
,
Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...
)Columbia University: CV: Mihalis Yannakakis
(accessed 12 November 2009)
is a professor of computer science at
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
. He is noted for his work in
computational complexity In computer science, the computational complexity or simply complexity of an algorithm is the amount of resources required to run it. Particular focus is given to computation time (generally measured by the number of needed elementary operations ...
,
databases In computing, a database is an organized collection of data or a type of data store based on the use of a database management system (DBMS), the software that interacts with end users, applications, and the database itself to capture and ana ...
, and other related fields. He won the Donald E. Knuth Prize in 2005.Knuth Prize
/ref>


Education and career

Yannakakis was born in Athens, Greece in 1953 and attended Varvakeio High School for his early education. He graduated from the
National Technical University of Athens The National (Metsovian) Technical University of Athens (NTUA; , ''National Metsovian Polytechnic''), sometimes known as Athens Polytechnic, a university in Athens, Greece. It is named in honor of its benefactors Nikolaos Stournaris, Eleni Tosi ...
in 1975 with a diploma in Electrical Engineering, and then earned his PhD in Computer Science from
Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...
in 1979. His dissertation was entitled "The Complexity of Maximum Subgraph Problems". In 1978 he joined
Bell Laboratories Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several lab ...
and served as Director of the Computing Principles Research Department starting from 1991 until 2001, when he left Bell laboratories and joined Avaya Laboratories. There he served as Director of the Computing Principles Research Department until 2002. In 2002 he joined
Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...
, where he was a professor of computer science, and left in 2003 to join
Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
in 2004, where he is currently serving as the Percy K. and Vida L. W. Hudson Professor of Computer Science. From 1992 to 2003, Yannakakis served on the editorial board of the ''
SIAM Journal on Computing The ''SIAM Journal on Computing'' is a scientific journal focusing on the mathematical and formal aspects of computer science. It is published by the Society for Industrial and Applied Mathematics (SIAM). Although its official ISO abbreviation i ...
'' and was the
editor-in-chief An editor-in-chief (EIC), also known as lead editor or chief editor, is a publication's editorial leader who has final responsibility for its operations and policies. The editor-in-chief heads all departments of the organization and is held accoun ...
between 1998 and 2003. He also was a member of the editorial board of the ''
Journal of the ACM The ''Journal of the ACM'' (''JACM'') is a peer-reviewed scientific journal covering computer science in general, especially theoretical aspects. It is an official journal of the Association for Computing Machinery. Its current editor-in-chief is ...
'' from 1986 to 2000. Other editorial board memberships include the ''
Journal of Computer and System Sciences The ''Journal of Computer and System Sciences'' (JCSS) is a peer-reviewed scientific journal in the field of computer science. ''JCSS'' is published by Elsevier, and it was started in 1967. Many influential scientific articles have been published ...
'', the ''Journal of Combinatorial Optimization'', and the ''Journal of Complexity''. He has also served on conference committees and chaired various conferences, such as the
ACM Symposium on Principles of Database Systems The ACM Symposium on Principles of Database Systems (PODS) is an international research conference on database theory, and has been held yearly since 1982. It is sponsored by three Association for Computing Machinery The Association for Com ...
and the IEEE Symposium on Foundations of Computer Science. As of June 2020, his publications have been cited close to 35,000 times, and he has an
h-index The ''h''-index is an author-level metric that measures both the productivity and citation impact of the publications, initially used for an individual scientist or scholar. The ''h''-index correlates with success indicators such as winning t ...
of 93.


Research

Yannakakis is known for his contributions to computer science in the areas of
computational complexity theory In theoretical computer science and mathematics, computational complexity theory focuses on classifying computational problems according to their resource usage, and explores the relationships between these classifications. A computational problem ...
,
database theory Database theory encapsulates a broad range of topics related to the study and research of the theoretical realm of databases and database management systems. Theoretical aspects of data management include, among other areas, the foundations of q ...
, computer aided verification and testing, and algorithmic graph theory. Among his contributions to complexity theory are two papers about the PCP theory and about
hardness of approximation In computer science, hardness of approximation is a field that studies the algorithmic complexity of finding near-optimal solutions to optimization problems. Scope Hardness of approximation complements the study of approximation algorithms by pro ...
. In the Annual ACM Symposium on Theory of Computing of 1988, Yannakakis and
Christos Papadimitriou Christos Charilaos Papadimitriou (; born August 16, 1949) is a Greek-American theoretical computer scientist and the Donovan Family Professor of Computer Science at Columbia University. Education Papadimitriou studied at the National Technical ...
introduced the definitions of the complexity classes Max-NP and Max-SNP. Max-NP and Max-SNP (which is a subclass of Max-NP) contain a number of interesting optimization problems, and it was shown by Yannakakis and Papadimitriou that these problems have some bounded error. These findings were able to explain the lack of progress that had been seen in the research community on the approximability of a number of optimization problems, including
3SAT 3sat (, ''Dreisat'') is a free-to-air German-language public service television channel. It is a generalist channel with a cultural focus and is jointly operated by public broadcasters from Germany ( ZDF, ARD), Austria ( ORF) and Switzerlan ...
, the Independent Set problem, and the
Travelling Salesman Problem In the Computational complexity theory, theory of computational complexity, the travelling salesman problem (TSP) asks the following question: "Given a list of cities and the distances between each pair of cities, what is the shortest possible ...
. Yannakakis and Carsten Lund presented a number of findings regarding the hardness of computing approximations at the Annual ACM Symposium on Theory of Computing of 1993. These findings demonstrated the difficulty of efficiently computing approximate solutions to a number of minimization problems such as
Graph coloring In graph theory, graph coloring is a methodic assignment of labels traditionally called "colors" to elements of a Graph (discrete mathematics), graph. The assignment is subject to certain constraints, such as that no two adjacent elements have th ...
and Set covering. Given the unlikely scenario that
NP-hard In computational complexity theory, a computational problem ''H'' is called NP-hard if, for every problem ''L'' which can be solved in non-deterministic polynomial-time, there is a polynomial-time reduction from ''L'' to ''H''. That is, assumi ...
problems such as Graph coloring and Set covering would be solved optimally in
polynomial time In theoretical computer science, the time complexity is the computational complexity that describes the amount of computer time it takes to run an algorithm. Time complexity is commonly estimated by counting the number of elementary operations p ...
, there had been many attempts to develop efficient approximation solutions for them; the results obtained by Yannakakis and Carsten proved the unlikelihood of achieving this task. In the area of
database theory Database theory encapsulates a broad range of topics related to the study and research of the theoretical realm of databases and database management systems. Theoretical aspects of data management include, among other areas, the foundations of q ...
, his contributions include the initiation of the study of acyclic database schemes, acyclic conjunctive queries, and non-two-phase locking. Acyclic database schemes are schemes that contain a single acyclic
join dependency In database theory, a join dependency is a constraint on the set of legal relations over a database scheme. A table T is subject to a join dependency if T can always be recreated by joining multiple tables each having a subset of the attributes of ...
(a join dependency is a relationship governing the joining of tables of the database) and a collection of functional dependencies; a number of researchers, including Yannakakis, pointed out the usefulness of these schemes by demonstrating the many useful properties they had: for example, the ability to solve many acyclic-scheme based problems in polynomial time, whereas the problem could easily have been NP-complete for other schemes. With regard to non
two-phase locking In databases and transaction processing, two-phase locking (2PL) is a pessimistic concurrency control method that guarantees conflict-serializability. Philip A. Bernstein, Vassos Hadzilacos, Nathan Goodman (1987) ''Concurrency Control and Recov ...
, Yannakakis demonstrated how knowledge about the structure of a database and the forms of various transactions executed on them could be used to establish whether a particular locking policy is safe or not. The commonly used two phase locking (2PL) policies consist of two stages – for locking and unlocking entities respectively – and to avoid such a policy it is necessary to impose some structure on the entities of a database; Yannakakis' results show how, by choosing a
hypergraph In mathematics, a hypergraph is a generalization of a Graph (discrete mathematics), graph in which an graph theory, edge can join any number of vertex (graph theory), vertices. In contrast, in an ordinary graph, an edge connects exactly two vert ...
resembling the consistency constraint-structure of a database, a locking policy that visits entities along the paths of this hypergraph will be safe. Such a policy need not be two-phase and these policies can be classified according to the connectivity of the above-mentioned hypergraph, 2PL policies being only one particular instance of these. Yannakakis went on to show that for the natural class of safe locking policies (L-policies), freedom from deadlocks is determined solely on the order in which entities are accessed by transactions, and from this derived simple conditions that would guarantee freedom from deadlocks for an L-policy. He has also contributed to the area of computer aided verification and testing, where he laid the rigorous algorithmic and complexity-theoretic foundations of the field. Some of his contributions include the designing of memory efficient algorithms for the verification of temporal properties of finite-state programs, determining the complexity of testing whether programs satisfy their specifications expressed in linear-time
temporal logic In logic, temporal logic is any system of rules and symbolism for representing, and reasoning about, propositions qualified in terms of time (for example, "I am ''always'' hungry", "I will ''eventually'' be hungry", or "I will be hungry ''until'' I ...
, and verifying that a model with timing constraints satisfies a given temporal property. Along with Alex Groce and Doron Peled, he introduced Adaptive Model Checking, showing that when inconsistencies are present between a system and the corresponding model, the results of the verification can be used to improve the model. He has also contributed to research on Message Sequence Charts (MSC), where it was shown that weak
realizability In mathematical logic, realizability is a collection of methods in proof theory used to study constructive proofs and extract additional information from them. Formulas from a formal theory are "realized" by objects, known as "realizers", in a way ...
is undecidable for bounded MSC-graphs and that safe-realizability is in
EXPSPACE In computational complexity theory, is the set of all decision problems solvable by a deterministic Turing machine in exponential space, i.e., in O(2^) space, where p(n) is a polynomial function of n. Some authors restrict p(n) to be a linear func ...
, along with other interesting results related to the verification of MSC-graphs.


Awards and recognition

Yannakakis is a member of both the
National Academy of Engineering The National Academy of Engineering (NAE) is an American Nonprofit organization, nonprofit, NGO, non-governmental organization. It is part of the National Academies of Sciences, Engineering, and Medicine (NASEM), along with the National Academ ...
and the
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
. He was awarded the seventh
Knuth prize The Donald E. Knuth Prize is a prize for outstanding contributions to the foundations of computer science, named after the American computer scientist Donald E. Knuth. History The Knuth Prize has been awarded since 1996 and includes an award of ...
for his contributions to theoretical computer science. He has also been awarded the Bell Labs Distinguished Member of Technical Staff Award and the Bell Labs President's Gold Award, in 1985 and in 2000 respectively. He is a Fellow of the ACM and also a Fellow of
Bell Laboratories Nokia Bell Labs, commonly referred to as ''Bell Labs'', is an American industrial research and development company owned by Finnish technology company Nokia. With headquarters located in Murray Hill, New Jersey, the company operates several lab ...
. He was elected fellow of the American Academy of Arts and Sciences (AAAS) in 2020.


References


External links


Home page at Columbia
{{DEFAULTSORT:Yannakakis, Mihalis 1953 births Living people Greek computer scientists American computer scientists Columbia School of Engineering and Applied Science faculty Knuth Prize laureates 1998 fellows of the Association for Computing Machinery Theoretical computer scientists National Technical University of Athens alumni Greek academics Members of the United States National Academy of Engineering Members of the United States National Academy of Sciences People from Athens