Traditional Worst-case Execution Time Research Articles

A Worst-Case Execution Time Analysis Approach Based on AOE Networks

To overcome disadvantages of traditional worst-case execution time (WCET) analysis approaches, this paper proposes a new WCET analysis approach based on AOE networks for ARM programs. By assigning the execution times of program segments to weights of directed edges, we reformulated the analysis of the WCET of the program as finding the longest path in a weighted directed graph. An algorithm implemented in this paper is used to search the longest path in the weighted directed graph and gives the WCET estimate finally. Experimental results have shown the analysis approach proposed in this paper is an effective way to obtain the safe and tight WCET estimate for ARM programs.

A Worst-case execution time analysis approach based on independent paths for ARM programs

To overcome disadvantages of traditional worst-case execution time (WCET) analysis approaches, we propose a new WCET analysis approach based on independent paths for ARM programs. Based on the results of program flow analysis, it reduces and partitions the control flow graph of the program and obtains a directed graph. Using linear combinations of independent paths of the directed graph, a set of feasible paths can be generated that gives complete coverage in terms of the program paths considered. Their timing measurements and execution counts of program segments are derived from a limited number of measurements of an instrumented version of the program. After the timing measurement of the feasible paths are linearly expressed by the execution times of program segments, a system of equations is derived as a constraint problem, from which we can obtain the execution times of program segments. By assigning the execution times of program segments to weights of edges in the directed graph, the WCET estimate can be calculated on the basis of graph-theoretical techniques. Comparing our WCET estimate with the WCET measurement obtained by the exhaustive measurement, the maximum error ratio is only 8.259 3 %. It is shown that the proposed approach is an effective way to obtain the safe and tight WCET estimate for ARM programs.

Worst Case Reaction Time Analysis of Concurrent Reactive Programs

Reactive programs have to react continuously to their inputs. Here the time needed to react with the according output is important. While the synchrony hypothesis takes the view that the program is infinitely fast, real computations take time. Similar to the traditional Worst Case Execution Time (WCET), the Worst Case Reaction Time (WCRT) of a program determines the maximal time for one reaction.In this paper, we present an algorithm to determine the WCRT of a program written in the synchronous language Esterel. This value gives an upper bound for the execution time when the program is executed on a reactive processor. Specifically, we consider the execution of the Esterel program on the Kiel Esterel Processor (KEP), a reactive processor that can execute Esterel-like instructions. Here the WCRT directly determines an upper bound on the instruction cycles per logical tick. The WCRT also gives a guideline for the execution time when the Esterel program is compiled to software by a simulation-based approach.We have implemented the WCRT analysis algorithm as part of an Esterel compiler for the Kiel Esterel Processor (KEP) and have measured an accuracy of analysis results of about 22% on average.

Integrating WCET Analysis into a Matlab/Simulink Simulation Model

Traditional worst-case execution time (WCET) analysis interfaces to the user either through high-level language source code or assembly/machine code. This paper demonstrates how WCET analysis can be integrated into high-level application design and simulation tools like Matlab/Simulink, thus providing a higher-level interface to WCET analysis. The paper shows necessary restrictions and adaptions to Matlab/Simulink that make code generated from the tool chain amenable to WCET analysis. It presents the interface between the Matlab/Simulink block set and WCET analysis and explains the steps performed during WCET analysis.