Reflections on Sir Henk van der Vorst

December 22, 2006

Jan Brandts, Bernd Fischer, and Andy Wathen

On July 22, friends and colleagues of Henk van der Vorst gathered to celebrate his early retirement from Utrecht University, where he had been a professor of applied mathematics since 1990. The event, a one-day symposium held in Utrecht, featured talks related to areas in which Van der Vorst has worked, along with fond and funny tributes from students, past and present, and a final---especially satisfying for being completely unexpected---twist.

Many in the SIAM community, in particular those who work in linear algebra, are aware of Van der Vorst's most outstanding contributions: incomplete Cholesky preconditioning, the BiCGSTAB iterative method for linear systems, and the Jacobi–Davidson algorithm for computing eigenvalues. The paper in which he introduced BiCGSTAB,* in fact, is known to the scientific community at large: In 2001, the Institute for Scientific Information identified it as the most cited paper in mathematics published in the 1990s (see Howard Elman's article "What's Hot? Study Points to Iterative Methods for Nonsymmetric Linear Systems," SIAM News, March 2001).

Van der Vorst has served SIAM journals well, not only as the author of widely cited papers, but also as a member of the editorial boards of SIAM Journal on Scientific Computing (1996–2004) and SIAM Journal on Matrix Analysis (2000–2003) and, since 2003, as editor-in-chief of SIMAX. (He has also been a member of the SIAM Council since 2001.)

In their talks at the symposium, the four main speakers touched on aspects of Van der Vorst's work: Dan Sorensen, Rice University, "Large Scale Eigenvalue Computation"; Per Christian Hansen, Copenhagen, "How I Learned to Stop Worrying and Love Semiconvergence"; Bernd Fischer, Lübeck, "Bi-CGSTAB Applied to the Thermoregulation of Premature Infants"; and Iain Duff, Rutherford Appleton Laboratory, UK, "The Perfect Preconditioner."

As mentioned earlier, students had a prominent place on the program as well, and they took advantage of the opportunity to express the warm regard and respect in which Van der Vorst is held by all. Other speakers alluded to activities that have made him a major figure not only in the Netherlands but throughout Europe.

Elected to the Royal Netherlands Academy of Arts and Sciences in 2002, Van der Vorst has held many important national positions. He is a frequent adviser to the Dutch multinationals Shell and Philips, for example, and as a member of committees of the Dutch Science Council NWO, he has influenced the direction of mathematics in the Netherlands.

Given these impressive contributions on so many levels, the unexpected conclusion to the symposium might not seem all that surprising. But when Yvonne van Rooij, who chairs the Board of Governors of Utrecht University, prefaced an announcement with the words "on behalf of our majesty," it was clear that something out of the ordinary was about to happen. And indeed it was: Queen Beatrix had named Van der Vorst a Knight in the Order of the Dutch Lion (Ridder in de Orde van de Nederlandse Leeuw).

This is an honor reserved for people who have made exceptional contributions to society. Readers might be interested in learning the names of a few of those who shared the distinction with Van der Vorst: Albert Uderzo, one of the creators of Astérix; Pieter van den Hoogenband, the Olympic swimmer who won gold medals in the 100-meter freestyle in both 2000 and 2004; and mayor Job Cohen of Amsterdam, named "European Hero of the Year 2005" by Time magazine.

An initially speechless Van der Vorst soon recovered his usual equanimity and addressed the group, setting the tone for the reception and dinner that followed. Many, including the guest of honour, were soon off to Düsseldorf and the conveniently scheduled GAMM–SIAM Conference on Linear Algebra, July 24–27, where Van der Vorst, the after-dinner speaker, titled his talk "Big Progress Goes with Small Steps."

Jan Brandts is a member of the research staff at the Korteweg–De Vries Institute for Mathematics at the University of Amsterdam. Bernd Fischer is a professor in the Institute of Mathematics, University of Lübeck. Andy Wathen is a reader in numerical analysis and a fellow of New College at Oxford University.

*H.A. van der Vorst, BiCGSTAB: A fast and smoothly converging variant of BiCG for the solution of non-symmetric linear systems, SIAM Journal on Scientific and Statistical Computing, Vol. 13, 1992.

Henk van der Vorst, surrounded by friends and colleagues who met to wish him well on his retirement from Utrecht University and ended up with a prestigious new honour to celebrate.

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