100 Jahre Allergie: Clemens von Pirquet - sein Allergiebegriff und das ihm zugrunde liegende Krankheitsverständnis

Summary: Coming from his clinical research in the field of infectiology and immunology the Viennese pediatrician Clemens von Pirquet (1874-1929) introduced the term "allergy" in 1906. With it he wanted to describe in general a change in reactivity of the organism, namely in time, quality and quantity. In contrast to the widely accepted use of the word "allergy" today, where it is restricted to specific immunologic hypersensitivity reactions against harmless foreign antigens, allergy in Pirquets sense comprised as general term likewise increases and decreases of the reactivity and so both "hyper-" and "hyposensitivity reactions". In the context with the expansion of allergy to the human predisposition Pirquet emphasized, that the change of reactivity does not only depend on exogenous substances (so called allergens), but also on endogenous factors of the organism itself. - The orientation towards the organism and his reactivity is the central idea, which can be found in the complete works of Pirquet from 1903 to 1929 and which is presented in this publication for the first time. It is the true essence of his theory of allerg

A Code Policy Guaranteeing Fully Automated Path Analysis

Calculating the worst-case execution time (WCET) of real-time tasks is still a tedious job. Programmers are required to provide additional information on the program flow, analyzing subtle, context dependent loop bounds manually. In this paper, we propose to restrict written and generated code to the class of programs with input-data independent loop counters. The proposed policy builds on the ideas of single-path code, but only requires partial input-data independence. It is always possible to find precise loop bounds for these programs, using an efficient variant of abstract execution. The systematic construction of tasks following the policy is facilitated by embedding knowledge on input-data dependence in function interfaces and types. Several algorithms and benchmarks are analyzed to show that this restriction is indeed a good candidate for removing the need for manual annotations

Comparison of Implicit Path Enumeration and Model Checking Based WCET Analysis

In this paper, we present our new worst-case execution time (WCET) analysis tool for Java processors, supporting both implicit path enumeration (IPET) and model checking based execution time estimation. Even though model checking is significantly more expensive than IPET, it simplifies accurate modeling of pipelines and caches. Experimental results using the UPPAAL model checker indicate that model checking is fast enough for typical tasks in embedded applications, though large loop bounds may lead to long analysis times. To obtain a tool which is able to cope with larger applications, we recommend to use model checking for more important code fragments, and combine it with the IPET approach

Towards Automated Generation of Time-Predictable Code

Knowledge of the worst-case execution time of software components is essential in safety-critical hard real-time systems. The analysis thereof is not trivial as the execution time depends on many factors, including the underlying hardware platform, the program structure, and the code produced by the compiler. Often, the execution time is variable and highly sensitive to the input data the program has to process. This paper presents a code transformation applicable in a compiler backend that produces time-predictable code. The resulting code contains a single input-data independent execution path, in order to obtain programs of stable timing behaviour. The transformation technique has been validated by applying it on a number of benchmarks. Experiments show a reduction of execution time variability, at acceptable costs for the single execution path

Scope-Based Method Cache Analysis

The quest for time-predictable systems has led to the exploration of new hardware architectures that simplify analysis and reasoning in the temporal domain, while still providing competitive performance. For the instruction memory, the method cache is a conceptually attractive solution, as it requests memory transfers at well-defined instructions only. In this article, we present a new cache analysis framework that generalizes and improves work on cache persistence analysis. The analysis demonstrates that a global view on the cache behavior permits the precise analyses of caches which are hard to analyze by inspecting cache state locally

A Formal Framework for Precise Parametric WCET Formulas

Parametric worst-case execution time (WCET) formulas are a valuable tool to estimate the impact of input data properties on the WCET at design time, or to guide scheduling decisions at runtime. Previous approaches to parametric WCET analysis either provide only informal ad-hoc solutions or tend to be rather pessimistic, as they do not take flow constraints other than simple loop bounds into account. We develop a formal framework around path- and frequency expressions, which allow us to reason about execution frequencies of program parts. Starting from a reducible control flow graph and a set of (parametric) constraints, we show how to obtain frequency expressions and refine them by means of sound approximations, which account for more sophisticated flow constraints. Finally, we obtain closed-form parametric WCET formulas by means of partial evaluation. We developed a prototype, implementing our solution to parametric WCET analysis, and compared existing approaches within our setting. As our framework supports fine-grained transformations to improve the precision of parametric formulas, it allows to focus on important flow relations in order to avoid intractably large formulas