John Sidney Rollett (2 October 1927 - 3 January 1995)

Obituary notice (Oxford University Gazette, 2 February 1995)

John Sidney Rollett, MA (MA Cambridge, PhD Leeds), 3 January 1995; Postdoctoral Fellow, California Institute of Technology, 1953-5; Pressed Steel Fellow, Chemical Crystallography Laboratory, 1956-8; Senior Research Officer, Computing Laboratory, 1958-77; University Lecturer in Numerical Mathematics, 1977-95; Fellow, St Cross College, 1965-95. Aged 67.

Oxford University Computing Laboratory Obituary

In the person of John Rollett, the Computing Laboratory has lost its longest serving staff member, and one of its most respected. His was the first academic appointment made by Leslie Fox in setting up the Computing Laboratory, and he remained here - as Senior Research Officer, for some time as Deputy Director, and later as University Lecturer - from March 1958 until his unexpected death on the eve of his retirement

John was born at Leiston, near Aldeburgh, but spent most of his childhood in Lincoln. In 1944, he went up to Magdalene College, Cambridge, to read Natural Sciences, after which he spent his two years of National Service as a shore-based Instructor in the Royal Navy. Following this he studied at the University of Leeds for a Ph.D. in Chemistry, working under Sir E.G. Cox on the determination of crystal structures, and then spent two years as a postdoctoral fellow with Linus Pauling at the California Institute of Technology before joining Dorothy Hodgkin's research group at the Chemical Crystallography Laboratory in Oxford. He continued to be closely associated with this group for many years after joining the Computing Laboratory, during which most of his work was concerned with improving techniques for the determination of crystal structures by computer analysis of their X-ray diffraction patterns. The principles and technical details of this work are set out in his book `Computing Methods in Crystallography' (Pergamon, 1965), the proceedings of a summer school which he organised and to which he was the major contributor.

This work, which continued through the 1970s, drew him into a more general study of techniques for practical optimisation and thence, as a necessary prerequisite, into research into the efficient solution of large systems of algebraic equations - in particular by means of conjugate-gradient and related iterative techniques, and by the use of parallel processors. His expertise in these areas was to prove invaluable following the creation in 1983 of the Institute for Computational Fluid Dynamics, in whose work he participated widely and enthusiastically.

He is remembered with affection, and much appreciation of the effort that he devoted to them, by the succession of research students whom he supervised throughout his career.

In 1965 he was elected as one of the founding fellows of St Cross College.

He served for many years on the Oxford Delegacy of Local Examinations, acting as its chairman from 1991 onwards. As such, he had the unenviable burden of guiding it through a stressful period when its independent viability was becoming increasingly uncertain, culminating in the University's decision to discharge the Delegacy and to transfer its operations to a wider body.

His recreations included fell-walking and choral singing, and he and his wife Constance, whom he married in 1953, were staunch members of the Oxford Harmonic Society. He died peacefully in his sleep while they were on holiday together in Spain. He leaves one surviving son and two daughters.

John Rollett and Chemical Crystallography (Tribute by Durward Cruickshank at Memorial Service, March 4, 1995)

In the summer of 1951 John Rollett and I went to the International Crystallographic Congress in Stockholm. After the meeting, we took the night train to Trondheim for a 10-day hike through the Jotunheim - the giant's home - the highest Norwegian mountain area. On the first day a flock of goats followed us as we made our way through the woods to the plateau above. The second day was misty and we saw nothing from the top of Norway's highest mountain. The surviving photographs show John standing in the snow, his feet shod in ex service boots and carrying his gas cape, clothed in flannel trousers, sports jacket, college scarf and beret - not exactly the outfit of today's high tech all-Goretex fell walker. But we had much enjoyment in the Jotunheim, despite getting wet through at least once.

On another day the sun shone brilliantly and we set off to go up Norway's second highest mountain. Half way up we rested; the sun was warm, the view was marvellous; and indolence was very tempting. So I announced that I proposed to succumb to temptation and to climb no further. John was properly shocked at such lethargy, but without more fuss he went on to the top alone. It was a very characteristic example of his admirable energy and determination.

His scientific career had begun in 1949 when he joined Professor Gordon Cox's group at Leeds in chemical crystallography. He did a splendid Ph.D. on the crystal structure of dimethyl triacetylene under the supervision of George Jeffrey. During that time Eddie Hughes, from Cal Tech - the pioneer in 1941 of the use of least squares in crystallography - was on sabbatical in Leeds.

Eddie recognised John's great abilities, and as a result John went as a post-doc in 1953 to Linus Pauling's lab in California. There he did more crystal structures, collaborating with Jack Dunitz and others. But more importantly he did some least-squares programming on the primitive Electrodata Datatron computer which Cal Tech had recently acquired.

As a spin off from that work, he got involved with Cohen and Dumond in their revision of the best values of the fundamental atomic constants of physics - the charge on the electron, the Avagadro number, etc. This analysis of variance led in 1955 to a much quoted paper on the Atomic Constants. Eddie Hughes told me later that Professor Dumond thought so well of John that he felt Cal Tech had been crazy not to have tried to keep John.

So in 1955, John returned to England to a Fellowship in Dorothy Hodgkin's laboratory. From then on Oxford was his base. Here in this University he made his great contributions to crystallographic computing. After a preliminary venture on the prototype Ferranti Pegasus computer, he turned his attention in January 1956 to the English Electric DEUCE computer which had been installed at the National Physical Laboratory. Very quickly he produced a string of programmes for complex crystallographic calculations. First of course, he had to work out the necessary very general algorithms to handle the 230 space groups of crystallography - in this he could build on his previous experience. Then he had to do the actual machine code programming. To those of us using the Ferranti Mark I machine in Manchester, the thought of programming DEUCE was a nightmare. John just lapped it up; he revelled in its complexities. He enjoyed conquering its possibilities.

The store capacity of DEUCE was then a mere 8000 words on drum, and some 400 words on faster access. A multiplication took 2 milliseconds; an addition was 30 times faster. It was possible to do other operations while multiplication was in progress - John wrote "it [was] possible to practise "time-sharing" to the point of doing four different things at once" - - of course, provided you were clever enough - and John was. He told me "I can usually keep the multiplier of DEUCE running about 3/4 of the time - which would be tough it I couldn't prepare the next multiplication meanwhile".

The programmes he produced were so good that many of the users in this country and abroad had no real idea of what John had done for them. A few users most certainly had that appreciation, but I do believe that his name ought to have appeared as a co-author on many papers reporting crystal structure determinations.

He continued his good work when Oxford got its Ferranti Mercury computer around 1958 - by then he was in the University Computing Laboratory. I can pick out only some highlights. In 1962 he organized in Oxford a Summer School on Computing Methods in Crystallography and edited the resulting book. The emphasis was not on programming, but on Methods. John gave more lectures than anyone else, and he delivered them, as always, very clearly, very audibly, and beautifully arranged. He had become very interested in matrix algebra, and the applications of latent roots and vectors in the convergence of iterative least-squares processes.

In late 1961 the UGC authorized the purchase of a new series of computers - the English Electric KDF9 - for delivery to Oxford and other universities two or three years later. John immediately wrote to me - 23 November 1961 - not only proposing cooperation in program design. "My feeling is that it matters more to establish common forms of lists, this time, than to discuss programming details. Previously I was willing to do anything about other data provided the planes tape was standard, but now I want standard lists of parameters, cell dimensions, form factors, symmetry operations, ...". This was the origin of a very effective collaboration between Oxford, Glasgow, Leeds and Sydney, which resulted in an extensive set of data structures agreed in May 1964. These Lists have allowed portability as programs have developed over the years and machines have changed. Indeed John's data structures, suitably updated, are a major feature of the current widely used Oxford system of programs called CRYSTALS.

Many of John's ideas remain extremely fruitful in crystallography. Only last month, I found great help in two of his papers from 1965 and 1970. Despite the switch of his main activity to the Computing Laboratory, he continued to be very interested in crystallography and crystallographers - in 1989 he contributed to an important paper in Acta Crystallographica on Statistical Descriptors.

John had been a friend of mine for 45 years. I felt a deep grief when I heard of his sudden death. On behalf of the crystallographic community in this country and abroad, I offer to Constance and Anthony, Penny and Helen and their families our deepest sympathy at their tragic loss. John will not be forgotten by crystallographers.

Appendix on some technical points

John Rollett joined Professor Cox's crystallographic group in 1949. Cox had a long involvement with crystallographic calculations: three-dimensional Fourier syntheses with hundreds of Fourier coefficients had been computed pre-war with the aid of Beevers-Lipson strips; punched card machines had been used since 1946/7; use of the Ferranti Mark I across the Pennines at Manchester University began in 1952.

The Electrodata Datatron at Cal Tech: words 10 binary coded decimal; drum 4000 words plus 20x4 words in quick access loops; x 8.5 msec, + 2 msec.

DEUCE: words 32 bits; 21 mercury delay lines of assorted lengths total 402 words; drum 8192 words; punched card in/out; x 2 msec, + 0.064 msec.

Mercury (1960): words 40 bits: ferrite cores 1024 words; drums 16,384 words; paper tape in/out; Floating Point x 0.300 msec, FP + 160 msec, 8 B-lines.

The operating systems and compilers initially available for the KDF9 computers were very disappointing. Despite the inter-university cooperation over crystallographic data structures, incompatibility of operating systems resulted in Oxford and Glasgow writing separate systems of crystallographic programs.

J Tilak Ratnanather

Associate Research Professor
Center for Imaging Science and
Institute for Computational Medicine,
Department of Biomedical Engineering,
The Johns Hopkins University

Campus address: Clark 308B;
Phone number: (410) 516-2927;
E-mail: tilak AT cis DOT jhu DOT edu