Extending WCET benchmark programs

Abstract: Today, traditional mechanical and electrical systems are replaced with special ICT (Information and communication technology) based solutions and with the invention of new technologies; this trend is increasing further more. This special ICT-based domain is called Real-time systems and today’s driveby-wire, electronic stability programs in car, control software in vehicles are just a few examples of real time systems. The task is a fundamental element of the software in a real-time system, and it is always necessary to know the longest execution time of a task, since missing a task’s deadline is a not allowed in a time critical hard real-time system. The longest execution time of a task or the Worst Case Execution Time (WCET) is estimated by WCET analysis. This estimation should be tight and safe to ensure the proper timing behavior of the real time system. But this WCET analysis is not always easy to perform, as the execution time of a task can vary by software characteristics like program flow or input data and also by hardware characteristics like speed of CPU, cache, pipeline and others. There are several methods and tools for WCET analysis. Some of them are commercial products and other are research prototypes. To verify and validate WCET analysis tools, evaluations of the tool’s properties are important, and thus WCET benchmark programs has emerged in recent years. These are intended for comparison between these tools properties and associated methods. The Mälardalen WCET benchmark suite has been maintained to evaluate the properties of various tool sets. In this thesis these benchmarks programs have been analyzed by SWEET (Swedish WCET Analysis Tool), the main tool used in this thesis. SWEET is a research prototype for WCET analysis. The main goal of this thesis work was to extend existing benchmark programs for WCET tools. It was obvious that most work load will be on benchmark program extension and at the beginning the work has been started by analyzing different small WCET benchmark programs. The evaluation of SWEET’s properties has been taken into a further extent by analyzing another benchmark program which is called PapaBench, a free real-time benchmark from Paparazzi project that represents a real-time application, developed to be embedded on different Unmanned Aerial Vehicles (UAV). Lots of time was required to complete the analyzing of PapaBench. The main reason behind this extensive work was that we decided to participate with SWEET in WCET Challenge 2011 (WCC 2011). So the purpose of the thesis ultimately turned into analyzing PapaBench instead of extending the WCET benchmark programs. The result of the thesis work is therefore mainly the analysis results from the analysis of PapaBench, which were reported to WCC 2011. The results from WCC 2011 are included in a paper presented at the WCET 2011 workshop, which took place in July 2011 in Porto, Portugal. Another part of the work was to examine real-time train control software which was provided by Bombardier. The main reason behind getting these industrial codes was to possibly add new benchmark programs to the Mälardalen WCET benchmark suite. A thorough manual study of this code has been performed to find out whether new benchmark programs could be found. However, due  to its structure and size, we decided that this code was not suitable to add to the Mälardalen WCET benchmark suite.