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The purpose of this paper is to introduce frameworks based on data-flow equations which provide for estimating the worst-case execution time (WCET) of (real-time) programs. These frameworks allow several different WCET analysis techniques, which range from nave approaches to exact analysis, provided exact knowledge on the program behaviour is available. However, data-flow frameworks can also be used for symbolic analysis based on information derived automatically from the source code of the program. As a byproduct we show that slightly modified elimination methods can be employed for solving WCET data-flow equations, while iteration algorithms cannot be used for this purpose.

The purpose of this paper is to show that indirect recursive procedures can be used for implementing real-time applications without harm, if a few conditions are met. These conditions ensure that upper bounds for space and time requirements can be derived at compile time. Moreover they are simple enough such that many important recursive algorithms can be implemented. In addition

Caches impose a major problem for predicting execution times of real-time systems since the cache behavior depends on the history of previous memory references. Too pessimistic assumptions on cache hits can result in worst-case execution time estimates that are prohibitive for real-time systems.

The purpose of this paper is to show that recursive procedures can be used for implementing real-time applications without harm, if a few conditions are met. These conditions ensure that upper bounds for space and time requirements can be derived at compile time. Moreover they are simple enough such that many important recursive algorithms can be implemented, for example Mergesort or recursive tree-traversal algorithms. 1 Introduction The most significant difference between real-time systems and other computer systems is that the system behavior must not only be correct but the result of a computation must be available within a predefined deadline. It has turned out that major progress in order to guarantee the timeliness of real-time systems can only be achieved if the scheduling problem is solved properly. Most scheduling algorithms assume that the runtime of a task is known a priori (cf. e.g. [8, 5, 10]). Thus the worst-case performance of a task plays a crucial role. The most dif...

Recurrence relations play an important role in the field of complexity analysis since complexity measures can often be elegantly expressed by systems of such relations. This justifies the interest in automatic, precise, efficient and correct systems able to solve or to approximate the solution of systems of recurrence relations. Assume such a system is built. Since closed-form solutions for recurrences of even modest complexity can be so big and complex to be unmanageable, how can confidence on such a system be gained? How can we quickly validate or perhaps disprove its results? And, in those cases where the exact solution is too complex to be of practical use, how can we trade precision for efficiency by approximating them from below and from above? We also concern ourselves with a problem related to the handling of sets of solutions of recurrence relations: how can we confine by means of a lower bound and an upper bound a set of such solutions? We provide some solutions to these problems where we are careful to rely, whenever possible, on fast integer computations and/or conditions that are easy to check in a completely automatic way. The ongoing experimental evaluation of these ideas is giving very promising results, showing order-of-magnitude speedups over the more traditional methods.

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. The purpose of this paper is to present several additions to Ada95 which improve real-time properties of the language. In detail, we introduce a new kind of loops, so-called discrete loops, we show that recursion can be used for real-time applications without harm, if a few conditions are met, and we present an approach how the interface of a class can be augmented by information concerning the worst-case time and space behavior. 1 Introduction The most significant difference between real-time systems and other computer systems is that the system behavior must not only be correct but the result of a computation must be available within a predefined deadline. It has turned out that major progress in order to guarantee the timeliness of real-time systems can only be achieved if the scheduling problem is solved properly. Most scheduling algorithms assume that the runtime of a task is known a priori. Thus the worstcase performance of a task plays a crucial role. The most difficu...

Within the last years, ambitions towards the definition of common interfaces and the development of open frameworks have been increasing the efficiency of research on WCET analysis. The Annotation Language Challenge for WCET analysis has been proposed with the intention to underline the importance of such common interfaces. Within this paper we present a list of essential ingredients for a common WCET annotation language. These selected ingredients comprise a number of features available in different WCET analysis tools and add several new concepts we consider important. The annotation concepts are described in an abstract format that can be instantiation at different representation levels. Keywords: Worst-case execution time (WCET) analysis, annotation languages, WCET annotation language challenge. 1 Why a Common WCET Annotation Language? The situation for WCET analysis is very heterogeneous. Within the real-time community it is a well known fact, that manual annotations are needed to assist non-perfect analyzes. Various tools exist providing different levels of sophistication. However, as the WCET Tool Challenge [8] has shown, few tools share ∗ This work has been partially supported by the Austrian