26,053 research outputs found
On Composable System Timing, Task Timing, and WCET Analysis
No full textThe complexity of hardware and software architectures used in today's
embedded systems make a hierarchical, composable timing analysis
impossible. This paper describes the source of this complexity in
terms of mechanisms and side effects that determine variations in the
timing of single tasks and entire applications. Based on these
observations, the paper proposes strategies to reduce the complexity.
It shows the positive effects of these strategies on the timing of
tasks and on WCET analysis
Classification of Code Annotations and Discussion of Compiler-Support for Worst-Case Execution Time Analysis
No full textTools for worst-case execution time (WCET) analysis
request several code annotations from the user.
However, most of them could be avoided or being annotated
more comfortably if the compilers would support
WCET analysis.
This paper provides a clear categorization of code
annotations for WCET analysis and discusses the positive
impact on code annotations a compiler-support on
WCET analysis would have
A Code Policy Guaranteeing Fully Automated Path Analysis
No full textCalculating 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
Vicuna: A Timing-Predictable RISC-V Vector Coprocessor for Scalable Parallel Computation
No full textIn this work, we present Vicuna, a timing-predictable vector coprocessor. A vector processor can be scaled to satisfy the performance requirements of massively parallel computation tasks, yet its timing behavior can remain simple enough to be efficiently analyzable. Therefore, vector processors are promising for highly parallel real-time applications, such as advanced driver assistance systems and autonomous vehicles. Vicuna has been specifically tailored to address the needs of real-time applications. It features predictable and repeatable timing behavior and is free of timing anomalies, thus enabling effective and tight worst-case execution time (WCET) analysis while retaining the performance and efficiency commonly seen in other vector processors. We demonstrate our architecture’s predictability, scalability, and performance by running a set of benchmark applications on several configurations of Vicuna synthesized on a Xilinx 7 Series FPGA with a peak performance of over 10 billion 8-bit operations per second, which is in line with existing non-predictable soft vector-processing architectures
Author Peter FitzSimons speaking at the National Library of Australia, Canberra, 13 November 2012 /
No full textTitle from acquisitions documentation.; Part of the collection: Portraits of author Peter FitzSimons speaking at the National Library of Australia, Canberra, 13 November 2012.; Acquired in digital format; access copy available online.; Mode of access: Online.; Photographed by a staff member of the National Library of Australia
Is Chip-Multiprocessing the End of Real-Time Scheduling?
No full textChip-multiprocessing is considered the future path for performance enhancements in computer architecture. Eight processor cores on a single chip are state-of-the art and several hundreds of cores on a single die are expected in the near future. General purpose computing is facing the challenge how to use the many cores. However, in embedded real-time systems thread-level parallelism is naturally used. In this paper we assume a system where we can dedicate a single core for each thread. In that case classic real-time scheduling disappears. However, the threads, running on their dedicated core, still compete for a shared resource, the main memory. A time-sliced memory arbiter is used to avoid timing influences between threads. The schedule of the arbiter is integrated into the worst-case execution time (WCET) analysis. The WCET results are used as a feedback to regenerate the arbiter schedule. Therefore, we schedule memory access instead of CPU time
A Formal Framework for Precise Parametric WCET Formulas
No full textParametric 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
Moral Good, the Beatific Vision, and God’s Kingdom Writings by Germain Grisez and Peter Ryan, S.J.. Edited by Peter J. Weigel
No full textFor close to half a century, the work of Germain Grisez has been highly influential, and his writings continue to receive considerable attention from philosophers and theologians of diverse viewpoints. His co-author for this work is the professor and noted moral theologian Fr. Peter Ryan, S.J., currently the executive director of the Secretariat of Doctrine and Canonical Affairs of the United States Conference of Catholic Bishops (USCCB). These two eminent scholars explore fundamental questions about Christian eschatology, moral theory, the purpose of human life, and the promise of human fulfilment. The authors examine Christian teaching on the final destiny of persons, investigating the meaning of God's kingdom, the hope of the beatific vision, and the centrality of moral goodness and divine grace in one's final end. This work is an ideal source for students, scholars, ministers and lay persons interested in basic questions of Christian theology, the philosophy of religion, ethical theory, and Catholic doctrin
Towards Automated Generation of Time-Predictable Code
No full textKnowledge 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
Murder on the mountain: author talk with Peter J. Wosh
No full textAuthor talk by Peter J. Wosh on May 5th, 2022, on his book, "Murder on the Mountain: crime, passion, and punishment in gilded age New Jersey.
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