John Francis is a British computer scientist and co-inventor of the QR algorithm for computing the eigenvalues and eigenvectors of matrices. This algorithm has been named as one of the 10 most important of the 20th century.
Francis was born in London in 1934. In 1954 he worked for the National Research Development Corporation (NRDC) and attended some lectures given by Christopher Strachey, one of the founders of denotational semantics, and a pioneer in programming language design. Between 1955 and 1956 John attended the University of Cambridge, but did not complete a degree. He then went back to the NRDC as an assistant to Strachey, where he became involved in flutter computations – leading to his work on QR.
In 1961 he left the NRDC to work at Ferranti Corporation, Ltd. and then at the University of Sussex. Subsequently, he had positions with various industrial organisations and consultancies. His interests encompassed artificial intelligence, computer languages, and systems engineering, although he never returned to the field of numerical computation.
By 1962, Francis had left the field of numerical analysis, and subsequently had no idea of the impact of his work on the QR algorithm, until contacted by Professors Gene Golub and Frank Uhlig in 2007, by which time he was retired. Still in good health, he was the opening speaker at a mini-symposium that marked 50 years of the QR algorithm, held at the 23rd Biennial Conference on Numerical Analysis in Glasgow in June 2009.
The QR algorithm allows the computation of eigenvalues of linear operators, which is arguably the single most useful mathematical ‘technology’ – for example, eigenvalue and eigenvector computations are behind Google’s original engine, the PageRank algorithm, which enabled a breakthrough in web-search.