Godfried Toussaint

Godfried Toussaint

Godfried T. Toussaint is a Research Professor of Computer Science at New York University Abu Dhabi (NYUAD) in Abu Dhabi, United Arab Emirates. He does research on various aspects of computational geometry, discrete geometry, and their applications: pattern recognition (k-nearest neighbor algorithm, cluster analysis), motion planning, visualization (computer graphics), knot theory (stuck unknot problem), linkage (mechanical) reconfiguration, the art gallery problem, polygon triangulation, the largest empty circle problem, unimodality (unimodal function), and others. Other interests include meander (art), compass and straightedge constructions, instance-based learning, music information retrieval, and computational music theory.

He has been editor and associate editor of a number of scientific journals. He is a co-founder of the Annual ACM Symposium on Computational Geometry, and the Annual Canadian Conference on Computational Geometry. He has published more than 360 papers and articles in journals and conference proceedings. He has an Erdős number of two due to his collaboration with David Avis and Richard Pollack.

Along with Selim Akl, he is an author and namesake of the efficient "Akl-Toussaint algorithm" for the construction of the convex hull of a planar point set. This algorithm exhibits a computational complexity with expected value linear in the size of the input. In 1980 he introduced the relative neighborhood graph (RNG) to the fields of pattern recognition and machine learning, and showed that it contained the minimum spanning tree, and was a subgraph of the Delaunay triangulation. These graphs are members of the family of proximity graphs. Three other well known proximity graphs are the nearest neighbor graph, the Urquhart graph, and the Gabriel graph. The first is contained in the minimum spannig tree, and the Urquhart graph contains the RNG, and is contained in the Delaunay triangulation. Since all these graphs are nested together they are referred to as the Toussaint hierarchy.

He has made contributions to other problems in computational geometry including minimum bounding box algorithms, rotating calipers, four-bar linkages, and the Erdős–Nagy theorem.

Mathematical research in music

He recently spent a year in the Music Department at Harvard University doing research on musical similarity, a branch of music cognition. Since 2005 he has also been a researcher in the Centre for Interdisciplinary Research in Music Media and Technology in the Schulich School of Music at McGill University. He applies computational geometric and discrete mathematics methods to the analysis of symbolically represented music in general, and rhythm in particular. In 2004 he discovered that the Euclidean algorithm for computing the greatest common divisor of two numbers implicitly generates almost all the most important traditional rhythms of the world. His application of mathematical methods for tracing the roots of Flamenco were covered in numerous publications in several languages, and were the focus of two Canadian television programs.

Awards

In 1978 he was the recipient of the Pattern Recognition Society's Best Paper of the Year Award. In 1985 he was awarded a two-year Izaak Walton Killam Senior Research Fellowship by the Canada Council for the Arts. In 1988 he received an Advanced Systems Institute Fellowship from the British Columbia Advanced Systems Institute. In 1995 he was given the Vice-Chancellor's Research Best-Practice Fellowship by the University of Newcastle in Australia. In 1996 he won the Canadian Image Processing and Pattern Recognition Society's Service Award for his "outstanding contribution to research and education in Computational Geometry." In May 2001 he was honored with the David Thomson Award for excellence in graduate supervision and teaching at McGill University. In 2009 he won a Radcliffe Fellowship from the Radcliffe Institute for Advanced Study at Harvard University to carry out a research project on the phylogenetics of the musical rhythms of the world.

Books and book chapters

• G. T. Toussaint, The Geometry of Musical Rhythm, Chapman and Hall/CRC, January 2013.
• G. T. Toussaint, Computational Geometry, Editor, North-Holland Publishing Company, Amsterdam, 1985.
• G. T. Toussaint, Computational Morphology, Editor, North-Holland Publishing Company, Amsterdam, 1988.
• I. Khoury, G. Toussaint, A. Ciampi, I. Antoniano, C. Murie, and R. Nadon, “Proximity-Graph-Based Tools for DNA Custering,” Encyclopedia of Data Warehousing and Mining (Second Edition), John Wang, Editor, Vol. IV Pro-Z, August 2008, pp. 1623–1631.
• E. D. Demaine, B. Gassend, J. O'Rourke, and G. T. Toussaint, “All polygons flip finitely... right?” Surveys on Discrete and Computational Geometry: Twenty Years Later, J. E. Goodman, J. Pach, and R. Pollack, Editors, in Contemporary Mathematics, Vol. 453, 2008, pp. 231–255.
• J. O'Rourke and G. T. Toussaint, "Pattern recognition," Chapter 51 in the Handbook of Discrete and Computational Geometry, Eds., J. E. Goodman and J. O'Rourke, Chapman & Hall/CRC, New York, 2004, pp. 1135–1162.
• M. Soss and G. T. Toussaint, “Convexifying polygons in 3D: a survey,” in Physical Knots: Knotting, Linking, and Folding Geometric Objects in R3, AMS Special Session on Physical Knotting, Linking, and Unknotting, Eds. J. A. Calvo, K. Millett, and E. Rawdon, American Mathematical Society, Contemporary Mathematics Vol. 304, 2002, pp. 269–285.
• G. T. Toussaint, “Applications of the Erdős–Nagy theorem to robotics, polymer physics and molecular biology,” Año Mundial de la Matematica, Sección de Publicaciones de la Escuela Tecnica Superior de Ingenieros Industriales, Universidad Politecnica de Madrid, 2002, pp. 195–198.
• J. O'Rourke and G. T. Toussaint, "Pattern recognition," Chapter 43 in the Handbook of Discrete and Computational Geometry, Eds., J. E. Goodman and J. O'Rourke, CRC Press, New York, 1997, pp. 797–813.
• G. T. Toussaint, “Computational geometry and computer vision,” in Vision Geometry, Contemporary Mathematics, Volume 119, R. A. Melter, A. Rozenfeld and P. Bhattacharya, Editors, American Mathematical Society, 1991, pp. 213–224.
• H. A. ElGindy and G. T. Toussaint, “Computing the relative neighbor decomposition of a simple polygon,” in Computational Morphology, G. T. Toussaint, Editor, North-Holland, 1988, pp. 53–70.
• J. R. Sack and G. T. Toussaint, “Guard placement in rectilinear polygons,” in Computational Morphology, G. T. Toussaint, Ed., North-Holland, 1988, pp. 153–176.
• G. T. Toussaint, “A graph-theoretical primal sketch,” in Computational Morphology, G. T. Toussaint, Ed., North-Holland, 1988, pp. 229–260.
• G. T. Toussaint, “Movable separability of sets,” in Computational Geometry, G.T. Toussaint, Ed., North-Holland Publishing Co., 1985, pp. 335–375.
• B. K. Bhattacharya and G. T. Toussaint, “On geometric algorithms that use the furthest point Voronoi diagram,” in Computational Geometry, G.T. Toussaint, Ed., North-Holland Publishing Co., 1985, pp. 43–61.