In memoriam Dirk Dekker (1927-2021)

Mathematician and former CWI employee Dirk Dekker has died at the age of 94.

Publication date
1 Dec 2021

We received the sad news that the mathematician Prof. Dr. Th. J. (Dirk) Dekker has died at the age of 94.

Dekker (1927-2021) graduated in mathematics in 1954 at the University of Amsterdam (UvA) and obtained his doctorate in 1958 at the same university under supervision of the topologist prof. Johannes de Groot on the thesis: 'Paradoxical Decompositions of Sets and Spaces'. 

After his doctorate, he joined the ‘Rekenafdeling’ at the Mathematisch Centrum, the predecessor of the current CWI. Under the supervision of Adriaan van Wijngaarden he developed into an internationally renowned numerical mathematician. 

Dirk Dekker (left) with Aad van Wijngaarden. Source:

One of Dekker's contributions from the early period is that he was the first to find a solution to the problem of how two processes can run on one computer without interfering with each other or crashing together: Dekker's algorithm for mutual exclusion (which has a Wikipedia page). 

The famous computer scientist Edsger Dijkstra wrote about this in his notes entitled 'Over de sequentialiteit van procesbeschrijvingen' (EWD35): "Dr. T. J. Dekker has the honour of being the first to find a solution [...] Dekker's solution dates from 1959 and for almost three years this solution lived on as a 'curiosity', until at the beginning of 1962 this type of problem suddenly became topical for me again and Dekker's solution became the starting point of my next attempts."

Dekker was Professor of Numerical Analysis at the University of Amsterdam (UvA) from 1971 to 1992 and was one of the founders of computer science as a separate discipline there in 1981. During his professorship he cooperated intensively with CWI on the development and implementation of numerical solution methods, courses, working groups and European projects. He retired in 1992.

We wish family and friends strength in coping with the loss of Dirk Dekker.

Thanks to Gerard Alberts, Daan Crommelin and Jan Kok for the historical information and Barry Koren for the reference to the photo of Dekker with Van Wijngaarden.