Stephen Warshall (November 15, 1935 – December 11, 2006) was an American

computer scientist A computer scientist is a person who is trained in the academic study of computer science. Computer scientists typically work on the theoretical side of computation, as opposed to the hardware side on which computer engineers mainly focus ( ...

. During his career, Warshall carried out research and development in

operating systems An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ef ...

compiler design In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...

, language design, and

operations research Operations research ( en-GB, operational research) (U.S. Air Force Specialty Code: Operations Analysis), often shortened to the initialism OR, is a discipline that deals with the development and application of analytical methods to improve dec ...

. Warshall died on December 11, 2006 of

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bl ...

at his home in

Gloucester, Massachusetts Gloucester () is a city in Essex County, Massachusetts, in the United States. It sits on Cape Ann and is a part of Massachusetts's North Shore. The population was 29,729 at the 2020 U.S. Census. An important center of the fishing industry and ...

. He is survived by his wife, Sarah Dunlap, and two children, Andrew D. Warshall and Sophia V. Z. Warshall.

Early life

Warshall was born in

New York City New York, often called New York City or NYC, is the most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the most densely populated major city in the U ...

and went to public school in

Brooklyn Brooklyn () is a borough of New York City, coextensive with Kings County, in the U.S. state of New York (state), New York. Kings County is the most populous Administrative divisions of New York (state)#County, county in the State of New York, ...

. He graduated from A.B. Davis High School in

Mount Vernon, New York Mount Vernon is a city in Westchester County, New York, United States. It is an inner suburb of New York City, immediately to the north of the borough of the Bronx. As of the 2020 census, Mount Vernon had a population of 73,893, making it th ...

and attended

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...

, receiving a

bachelor's degree A bachelor's degree (from Middle Latin ''baccalaureus'') or baccalaureate (from Modern Latin ''baccalaureatus'') is an undergraduate academic degree awarded by colleges and universities upon completion of a course of study lasting three to six ...

in mathematics in 1956. He never received an advanced degree since at that time no programs were available in his areas of interest. However, he took graduate courses at several different universities and contributed to the development of

computer science Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includin ...

and

software engineering Software engineering is a systematic engineering approach to software development. A software engineer is a person who applies the principles of software engineering to design, develop, maintain, test, and evaluate computer software. The term ' ...

. In the 1971–1972 academic year, he lectured on

at French universities.

Employment

After graduating from Harvard, Warshall worked at ORO (Operation Research Office), a program set up by

Johns Hopkins Johns Hopkins (May 19, 1795 – December 24, 1873) was an American merchant, investor, and philanthropist. Born on a plantation, he left his home to start a career at the age of 17, and settled in Baltimore, Maryland where he remained for most ...

to do research and development for the

United States Army The United States Army (USA) is the land warfare, land military branch, service branch of the United States Armed Forces. It is one of the eight Uniformed services of the United States, U.S. uniformed services, and is designated as the Army o ...

. In 1958, he left ORO to take a position at a company called Technical Operations, where he helped build a research and development laboratory for military software projects. In 1961, he left Technical Operations to found Massachusetts Computer Associates. Later, this company became part of Applied Data Research (ADR). After the merger, Warshall sat on the board of directors of ADR and managed a variety of projects and organizations. He retired from ADR in 1982 and taught a weekly class in Biblical Hebrew at Temple Ahavat Achim in Gloucester, Massachusetts.

Warshall's algorithm

There is an interesting anecdote about his

proof Proof most often refers to: * Proof (truth), argument or sufficient evidence for the truth of a proposition * Alcohol proof, a measure of an alcoholic drink's strength Proof may also refer to: Mathematics and formal logic * Formal proof, a con ...

that the

transitive closure In mathematics, the transitive closure of a binary relation on a set is the smallest relation on that contains and is transitive. For finite sets, "smallest" can be taken in its usual sense, of having the fewest related pairs; for infinit ...

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...

, now known as Warshall's algorithm, is correct. He and a colleague at Technical Operations bet a bottle of

rum Rum is a liquor made by fermenting and then distilling sugarcane molasses or sugarcane juice. The distillate, a clear liquid, is usually aged in oak barrels. Rum is produced in nearly every sugar-producing region of the world, such as the Phi ...

on who first could determine whether this

always works. Warshall came up with his

overnight, winning the bet and the rum, which he shared with the loser of the bet. Because Warshall did not like sitting at a desk, he did much of his creative work in unconventional places such as on a

sailboat A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture. Types Although sailboat terminology ...

in the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by ...

or in a

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

lemon The lemon (''Citrus limon'') is a species of small evergreen trees in the flowering plant family Rutaceae, native to Asia, primarily Northeast India (Assam), Northern Myanmar or China. The tree's ellipsoidal yellow fruit is used for culin ...

orchard An orchard is an intentional plantation of trees or shrubs that is maintained for food production. Orchards comprise fruit- or nut-producing trees which are generally grown for commercial production. Orchards are also sometimes a feature of la ...

References

*
Journal of the ACM bibliography – Selected citations of Warshall paperStephen Warshall, ''Boston Globe'', Obituaries, December 13, 2006

Early life

Employment

Warshall's algorithm

References

Further reading

See also