An interview with IAIN S. DUFF Conducted by Thomas Haigh On 30 & 31st August, 2005 In East Hagbourne and Chilton, United Kingdom Interview conducted by the Society for Industrial and Applied Mathematics, as part of grant # DE-FG02-01ER25547 awarded by the US Department of Energy. Transcript and original tapes donated to the Computer History Museum by the Society for Industrial and Applied Mathematics © Computer History Museum Mountain View, California ABSTRACT Iain S. Duff explores the whole of his career to date. Duff grew up in Glasgow, attending The High School before earning a first class degree in Mathematics and Natural Philosophy from the University of Glasgow in 1969. He discusses the mathematical curriculum there, and recounts his early computing experiences as a summer fellow with IBM. Duff won a Carnegie Fellowship for postgraduate work at Oxford, culminating in a D.Phil. conferred in 1972. At Oxford he worked with the numerical analysis group and wrote his thesis on the analysis of sparse systems under the direction of Leslie Fox. While working toward his degree, Duff was already collaborating with Alan Curtis, Michael Powell, and John Reid at the nearby AERE Harwell nuclear power research center. His interest in sparse matrices was cemented by a 1971 visit to IBM’s Yorktown Heights laboratory for a conference, where he first met colleagues such as Alan George, Ralph Willoughby and Fred Gustavson. In 1972, Duff went to the United States on a Harkness postdoctoral fellowship, spending time at SUNY Stony Brook with Reggie Tewarson and Stanford, where he got to know Gene Golub. In 1973 he became a computing lecturer at Newcastle University, before returning to Harwell as a researcher in 1975. He continued to work on sparse matrix methods, establishing himself as a leading researcher in the area, through pioneering work with John Reid on multifrontal methods, a series of widely read review articles, and an influential book written in collaboration with Reid and Al Erisman. Duff rose within Harwell, becoming leader of its numerical analysis group in 1986. He explores in detail the development and composition of this group, paying particular attention to the Harwell Subroutine Library, a collection of numerical subroutines developed within Harwell from the mid-1960s on and widely distributed to other sites. Duff explains its history, evolution, areas of strength, sources of routines, documentation methods, distribution practices, relationship to the NAG library, and attempts at commercial exploitation. In 1990 Duff led his group from Harwell to the nearby Rutherford Appleton Laboratory, as government cuts and shifts in priorities threatened its future at Harwell. Since 1987 Duff has also led the Parallel Algorithms group at CERFACS in Toulouse, and discusses the origins of CERFACS, the composition and functioning of his group, and its involvement in the MUMPS and PARASOL projects to create parallel multifrontal solvers for sparse systems. Duff worked on various forms of BLAS, including contributions to the Level 3 BLAS specifications (with Jack Dongarra and others) and development of the Sparse BLAS standard (with Mike Heroux and Roldan Pozo). Duff also reviews his roles in a number of societies, including SIAM (as a Council member and Trustee), IMA (including editorship of its Journal of Numerical Analysis), LMS, ACM SIGNUM and SMAI, and his work as a consultant on supercomputing issues to the governments of countries including Malaysia, Sweden, Germany and the USA. HAIGH: Thank you very much for agreeing to take part in the interview. I wonder if you could begin just by talking in general terms about your early life and family background. DUFF: Yes, sure. Well, thank you for inviting me to participate in this. I don’t know, maybe it could be regarded as an honor, but it’s certainly very interesting to talk about one’s life. I’m very impressed by the background that you’ve already provided. You seem to know more about me than I do about myself. I guess I’m very proud of coming from the city of Glasgow in Scotland where I was born and brought up, went to high school and took my first degree at university. The family background, my father was in life insurance and his father was a shipbuilder or a tool maker, in fact, with John Brown’s Shipyard in Glasgow, so our roots are pretty strong in the classical tradition. From an early stage, I found mathematics easy, I would say. I’m not sure how excited I was; it was just the subject that you didn’t have to do any homework in and you could still get very high percentages and good marks, which made it attractive to me so I could do other things like play sports and be an ordinary kid when I was at school. The early education was in local primary schools where we lived in Glasgow. Then I went to what’s called the High School of Glasgow, which was an old-fashioned grammar school, which is to say it was selective in terms of people having to pass entrance exams to go to it. But it was a corporation school at the time. It has since, in fact, gone private, but it was a regular state school at the time I was there. That school, of course, emphasized quite a lot in the classics, as grammar schools would do. So by the time I came to what they call the Scot Bac now, or the Scottish Higher Certificate Exams, which you sit in five or six subjects, rather than the more specialized A Levels in England, I was really left with the choice of doing either Latin and Greek at university, which is what I was doing in the highers, or doing math, physics, and chemistry, which were the science subjects of choice at the time. Again, the choice was actually not an easy one, which may be a bad thing. Maybe it shows that I’m not just a total natural mathematician. But I opted for the science subjects and mathematics for the same reason, that I found them easy and you didn’t have to do a huge amount of reading or preparation for the exams. HAIGH: Would that have been a decision that you made when you were 15? DUFF: No, this would be a little later. 15 would be the kind of equivalent of O Levels. In the Scottish System, the decision is delayed because you do quite a lot more subjects at the higher level of school, so this is a decision that I would have made at 17 or 18, really, about a year before I went to university. I stayed on for the extra year at school because I was enjoying it so much and I was running a lot of societies, involved in quite a lot of activities at the school, although I could have left for university a year early. So as I said, it wasn’t exactly a toss-up between the two sides of things, but it was certainly something I looked at really carefully. And I still like things like history and classics, almost as a hobby. HAIGH: So while we’re talking about these topics, is there anything you would say from your experience and upbringing in Glasgow that had a particular effect on the way that you approached your later career, that you think had shaped your personal philosophy? Iain Duff, August 2005 3 DUFF: Well, I think people who are sort of energetic and honest and upfront, and I guess even friendly and enthusiastic, is an important thing in the sort of environment I was brought up in in Glasgow. I would like to think that that has continued and influenced my whole life since then. I do get very enthusiastic about things I do—about mathematics, about new maths analysis, about research topics that I’m doing nowadays. That’s something that I’ve always been enthusiastic about. I was enthusiastic about mathematics in school, for example. So this kind of general flavor of life was very strong there, I would say. I was going to say in the beginning, that I value very much the fact and the background of being brought up in what to my mind is still one of the best cities in the world! A bit biased, but that’s right. And of course, it was automatic to go to the University in Glasgow. Oxford and Cambridge just don’t really feature in the Scottish psyche. At that time, at least, anyway. So the best thing that you could do was to go to your local university and, in fact, I stayed at home during that time, which might sound unusual. But in fact, one of the benefits of being at home is that the university year is then a 52-week year, so all activities continue throughout the summer, unlike dormitory or residential or campus universities where they are only functioning for the term time. So there were good and bad points about staying home, of course, but I think there were a lot of good points. Well, there were bad points; it wasn’t until I went to Oxford that I had any sort of independence in terms of living separately. HAIGH: You had mentioned that one of the things that you had liked about mathematics was that if you were good at it, you didn’t have to do that much work. Did you also enjoy those technical kinds of hobbies like chemistry sets or building radios? DUFF: [Laughs] Well, I tried to build radios; I wasn’t very good at that.