Tue, June 15, 2021


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Remembering Aisla Land (1927 – 2021)

By Jonathan Rosenhead and László Végh

Ailsa Land was one of the most significant innovators in the techniques of Operational Research, and a major figure in the development of Operational Research education in the United Kingdom. Her work on the branch-and-bound method in integer programming introduced an approach that is still a cornerstone in mathematical optimisation. She was also the lynchpin for 30 years of the MSc programme at the London School of Economics, one of the first such courses in the country. When she received her Chair in 1980 she was the first woman to become a full professor in Operational Research in the United Kingdom, and we are unaware of any earlier such appointment worldwide.

It was her pioneering paper with Alison Harcourt (neé Doig), published in Econometrica in 1960, that introduced what later came to be called the branch-and-bound method in integer programming. This paper led to the first successful computer implementations for integer programming and played a pivotal role in the rapid development of mixed-integer programming. Sixty years on, it is still a key principle in contemporary integer programming solvers and methodologies and is a staple topic in any mathematical programming course. Land and Doig has been cited, and applied, many thousands of times.

Together with her collaborators and students, Ailsa made fundamental contributions to a wide range of optimisation problems, among them quadratic programming, bicriteria decision analysis, statistical data fitting, data envelopment analysis and combinatorial auctions. Her 1955 paper with George Morton was one of the early works to study the travelling salesman problem, and she continued to make significant contributions towards this problem over decades.

From the beginning of her career, she was engaged in applying the newly emerging mathematical programming techniques to practical problems. Her PhD thesis applied linear programming (also known as activity analysis at the time) to a coal transportation problem, and the branch-and-bound method was motivated by a model of refinery operations for British Petroleum.

Ailsa was also a pioneer in computational Operational Research. Once computers became available at the University of London and then at LSE, she started developing well-tested and robust computer implementations of important optimization methods. Her 1973 book Fortran Codes for Mathematical Programming: Linear, Quadratic and Discrete, jointly with Susan Powell, made their computer codes freely available to the OR community, an early example of open shared code and its creative documentation.

In the late 1950s, together with her LSE colleague George Morton, she initiated a two-year diploma, soon transformed into a masters degree, in Operational Research in collaboration with the British Iron and Steel Research Association. Their graduate trainees formed the initial core of students on the degree. This was one of the first two postgraduate degrees in OR in the country and in its 60 years of existence several thousand students graduated from it.

The OR group staff grew steadily in size, and Ailsa established an active research group, supervising numerous masters and PhD students, many of whom rose to positions of academic leadership around the world.

Ailsa’s relaxed and supportive style made the growing OR group a particularly harmonious and collaborative venture. Personally, she was remarkably successful in avoiding involvement in academic politics and committee work whether within LSE or in the wider OR world. Had she not taken early retirement in 1987 it would have been her turn to head the larger department, Statistical and Mathematical Sciences, within which OR was then embedded. As it was, she could say “Now I’m retired I can do some research!” – which she continued actively to do.

Ailsa Land (nee Dicken) was born and grew up in the West Midlands. She also spent some of the war years in Canada with her mother and they both enrolled in the Canadian Women’s Army Corps. After the war, she spent her student years and her entire career at LSE. She enrolled as a BSc Econ student in 1946, obtained her PhD in 1956, and occupied, in turn, every academic rank from Research Assistant to Professor, after which she continued her association with LSE as an Emeritus Professor pursuing active research work.

It was at LSE in 1950 that she met her fellow research assistant Frank Land. They married in 1953, and their family grew to a son and two daughters, seven grandchildren and two great-grandchildren, who survive her. Frank was a pioneer in information systems research and is Professor Emeritus at LSE.

Ailsa’s academic achievements have been recognised by the Harold Larnder Prize of the Canadian Operational Research Society in 1994, and by the Beale Medal of the British OR Society in 2019. LSE now offers the Ailsa Land Prize for the best overall performance by a student on the MSc Operations Research & Analytics. She will be the posthumous recipient of the EURO 2021 Gold Medal, the highest distinction within Operational Research in Europe, awarded by the Association of European Operational Research Societies.