Andrew R. Conn was born in London on Aug. 6, 1946, and died at his home in Westchester County, NY, on Mar. 14, 2019. He played a pioneering role in nonlinear optimization starting in the early 1970s, and he remained very active in the field until shortly before his death. Andy obtained his B.Sc. with honours in Mathematics at Imperial College, London, in 1967, and his Ph.D. from the University of Waterloo in 1971. He was a faculty member at Waterloo for 18 years starting in 1972, and then moved to the IBM T.J. Watson Research Center in Yorktown Heights, NY, where he spent the rest of his career.

Andy's research interests were extensive but centered on nonlinear optimization. They were typically motivated by algorithms, and included convergence analysis, applications and software. His first published paper, Constrained optimization using a nondifferentiable penalty function, which appeared in SIAM J. Numer. Anal. in 1973, was already quite influential, helping to pave the way for the eventually widespread use of exact penalty functions in nonlinear programming. Later work included an extraordinarily productive collaboration with Nick Gould and Philippe Toint, resulting in more than 20 publications by these three authors alone. One highlight of this collaboration was the definitive treatise Trust Region Methods (2000), the first book in the optimization series published by the Mathematical Programming Society (MPS, later MOS) in collaboration with SIAM. Another highlight was the LANCELOT software for large-scale constrained optimization, for which the authors were awarded the prestigious Beale–Orchard-Hays Prize for Excellence in Computational Mathematical Programming in 1994. A third highlight was the introduction of the influential Constrained and Unconstrained Testing Environment (CUTE). In more recent years, Andy became interested in derivative-free optimization (DFO) and, together with Katya Scheinberg and Luis Nunes Vicente, published several papers on DFO as well as a book, Introduction to Derivative-Free Optimization (MPS-SIAM Series on Optmization, 2009), for which they were awarded the Lagrange Prize in Continuous Optimization by MOS and SIAM in 2015. The citation states that the book includes a groundbreaking trust region framework for convergence that has made DFO both principled and practical.

Andy is survived by his wife Barbara, his mother and four siblings in England, his daughter Leah and his son Jeremy, and three grandchildren. He will be greatly missed by his family, the optimization community, and his many friends.