Static WCET Analysis Research Articles

OmpTG: From OpenMP Programs to Task Graphs

Real-time systems are shifting them from single-core to multi-core processors. Software must be parallelized to fully utilize the computation power of multi-core architectures. OpenMP is a promising framework to develop parallel real-time software on multi-cores. OpenMP programs keep certain similarity to real-time task graph models, and this motivates much recent work done on real-time scheduling of OpenMP tasks. However, these studies conduct evaluations with randomly generated task graphs, which cannot well capture the structure features of realistic OpenMP programs. To fill the gap between theoretical real-time scheduling research and the OpenMP software reality, we develop an ompTG tool for transforming OpenMP programs into parallel task graphs. ompTG prepares a way to exhibit OpenMP such that the researchers in real-time community can easily understand: An OpenMP system consists of a set of tasks. There are interdependencies among tasks, and each task has an intra structure of the control-flow graph. Besides the topology of OpenMP tasks, we also provide a safe WCET for each vertex of OpenMP task graphs by using static WCET analysis techniques. Moreover, we derive the flow facts, e.g, infeasible path and loop bounds for the task graph, which is necessary information for real-time scheduling and analysis. As a case study, we collect 12 OpenMP programs from the BOTS benchmark, and transform them into task graphs, demonstrating the usage of ompTG.

Parallelizing Industrial Hard Real-Time Applications for the parMERASA Multicore

The EC project parMERASA (Multicore Execution of Parallelized Hard Real-Time Applications Supporting Analyzability) investigated timing-analyzable parallel hard real-time applications running on a predictable multicore processor. A pattern-supported parallelization approach was developed to ease sequential to parallel program transformation based on parallel design patterns that are timing analyzable. The parallelization approach was applied to parallelize the following industrial hard real-time programs: 3D path planning and stereo navigation algorithms (Honeywell International s.r.o.), control algorithm for a dynamic compaction machine (BAUER Maschinen GmbH), and a diesel engine management system (DENSO AUTOMOTIVE Deutschland GmbH). This article focuses on the parallelization approach, experiences during parallelization with the applications, and quantitative results reached by simulation, by static WCET analysis with the OTAWA tool, and by measurement-based WCET analysis with the RapiTime tool.

An efficient algorithm for parametric WCET calculation

Static WCET analysis is a process dedicated to derive a safe upper bound of the worst-case execution time of a program. In many real-time systems, however, a constant global WCET estimate is not always so useful since a program may behave very differently depending on its configuration or mode. A parametric WCET analysis derives the upper bound as a formula rather than a constant. This paper presents a new algorithm that can obtain a safe parametric estimate of the WCET of a program. This algorithm is evaluated on a large set of benchmarks and compared to a previous approach to parametric WCET calculation. The evaluation shows that the new algorithm, to the cost of some imprecision, scales much better and can handle more realistic programs than the previous approach.