Roger Fletcher. 29 January 1939—15 July 2016

Roger Fletcher was a pioneering, British, applied mathematician, who specialized in numerical analysis and, most particularly, computational optimization. His extremely creative work covered all facets of the area: clever design, inspired analysis and detailed implementation. His distinguished career took him from his PhD and early lectureship in the Computing Laboratory at the University of Leeds, via the Theoretical Physics Division at the Atomic Energy Research Establishment in Harwell, to his ultimate, long-term position as professor of optimization and Baxter Professor of Mathematics at the University of Dundee. He was the ‘F’ in the highly influential FR, DFP and BFGS methods for unconstrained optimization, and the inventor of the exact augmented Lagrangian, filterSQP and filterSD methods that apply when constraints are involved. In addition, he made significant contributions to a wide range of other methods and application areas. Roger Fletcher was an inspiration to his students and collaborators alike. He stood at the forefront of a subject that is key to the understanding of much of modern science, engineering, planning and economics.