Experiments at the frontier of knowledge in fundamental physics have reached an unprecedented size and complexity. For example, the Large Hadron Collider (LHC) at the CERN research center in Geneva is 27 kilometers long and has four detectors with diameters as large as 25 meters. It was at CERN in 2012 that the team working on the LHC discovered the Higgs boson, an elementary particle with a deep connection to the laws of nature, addressing questions about the stability of the universe. Over time such research will hopefully give new insights into what the world is made of.

Another such accelerator, the International Linear Collider, is planned to be built in Japan. The extensive design and simulation studies that are an essential element of the project build planning phase, often take more time than the run time of the accelerator itself. An application called WHIZARD enables physicists to run future experiments, on their computers, in preparation for a new collider.

WHIZARD is an easy-to-use tool for particle physics simulations. It is written in modern, object-oriented Fortran and OCaml. WHIZARD uses many modern programming features of the standards Fortran2003 and Fortran2008. The WHIZARD team is currently mainly located at three places: the DESY research center in Hamburg, the University of Siegen and the University of Würzburg.

WHIZARD is under continuous development. The application’s calculations have to keep up with the contemporary state of the theory, increasing the accuracy of WHIZARD’s predictions, and the application has to be adapted to users’ changing requirements. The extensive testing and debugging ensures that WHIZARD can be used smoothly by its global user base.

For this ongoing work, the WHIZARD developers make full use of the NAG Fortran Compiler, renowned for its excellent checking capabilities. The NAG Compiler builds the code in a significantly shorter amount of time than other compilers, enabling much quicker development and debugging cycles. Memory leaks have been identified using the Compiler traceback facility, to reduce WHIZARD’S memory usage, and code quality is enhanced further by referring to the Compiler’s detailed error messages, both during build and run-time.

Christian Weiss, a member of the WHIZARD development group, said: “By using the NAG Fortran Compiler in the development and ongoing use of the WHIZARD application we see two key tangible benefits. The first is the improvement in the quality of the code which is imperative for the portability of the application and the accuracy of WHIZARD’s computational results. The second is the substantial reduction in development time which probably saved me one or two months of my PhD time.”

The progress of WHIZARD is presented regularly on numerous conferences and scientific papers.


WHIZARD was initially developed as a tool to describe electroweak physics of multiple weak bosons and the Higgs boson. Hence, the acronym: WHiZard, which stood for ‘W, Higgs, Z, And Respective Decays’.