Reversibility

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Jinkyu Lee - One of the best experts on this subject based on the ideXlab platform.

  • Time-Reversibility for Real-Time Scheduling on Multiprocessor Systems
    IEEE Transactions on Parallel and Distributed Systems, 2017
    Co-Authors: Jinkyu Lee
    Abstract:

    The real-time systems community has widely studied real-time scheduling, focusing on how to guarantee schedulability (i.e., timely execution) of a set of real-time tasks. However, there still exist a number of task sets that are actually schedulable by a target scheduling algorithm, but proven schedulable by none of existing schedulability tests, especially on a multiprocessor. In this paper, we propose a new paradigm for real-time scheduling, called time-Reversibility, which views real-time scheduling under a change in the sign of time, and present how to utilize the paradigm for schedulability improvement. To this end, we first define the notion of a time-reversed scheduling algorithm and a time-reversible schedulability test; for example, the time-reversed scheduling algorithm against Earliest Deadline First (EDF) is Latest Release-time First (LRF). Then, we develop time-Reversibility theories for schedulability improvement, which utilizes the definitions so as to compose schedulability. Finally, we generalize the definitions and theories to job-level dynamic-priority scheduling in which the priority of a job may vary with time, such as Earliest Deadline first until Zero Laxity (EDZL). Specifically, we accommodate time-varying job parameters to the time-Reversibility definitions, and adapt the time-Reversibility theories for the additional necessary deadline-miss conditions specialized for a class of job-level dynamic-priority scheduling algorithms. As case studies, we demonstrate that the time-Reversibility theories help to find up to 13.6 percent additional EDFand EDZL-schedulable task sets.

  • Time-Reversibility of Schedulability Tests
    2014 IEEE Real-Time Systems Symposium, 2014
    Co-Authors: Jinkyu Lee
    Abstract:

    For timing guarantees of a set of real-time tasks under a target scheduling algorithm, a number of schedulability tests have been studied. However, there still exist many task sets that are potentially schedulable by a target scheduling algorithm, but proven schedulable by none of existing schedulability tests, especially on a multiprocessor platform. In this paper, we propose a new notion of time-Reversibility of schedulability tests, which yields tighter schedulability guarantees by viewing real-time scheduling under a change in the sign of time. To this end, we first define the notion of a time-reversed scheduling algorithm against a target scheduling algorithm, for example, the time-reversed scheduling algorithm against EDF (Earliest Deadline First) is LCFS (Last-Come, First-Served), and the converse also holds. Then, a schedulability test for a scheduling algorithm is said to be time-reversible with respect to schedulability, if all task sets deemed schedulable by the test are also schedulable by its time-reversed scheduling algorithm. To exploit the notion of time-Reversibility for tighter schedulability guarantees, we not only prove time-Reversibility of an existing schedulability test, but also develop a new time-reversible schedulability test, both of which cover additional schedulable task sets. Next, we generalize the time-Reversibility theory towards partial execution. Utilizing the notion, we can assure the schedulability of a task under a target scheduling algorithm in a divide-and-conquer manner: (i) the first some units of execution guaranteed by a schedulability test for the scheduling algorithm, and (ii) the remaining execution guaranteed by a time-reversible (with respect to partial execution) schedulability test for its time-reversed scheduling algorithm. Such a divide-and-conquer approach has not been directly applied to existing schedulability tests in that they cannot address (ii) effectively. As a case study, this paper develops RTA (Respons- -Time Analysis) for LCFS, proves its time-Reversibility, and applies the divide-and-conquer approach to the test along with an existing EDF schedulability test. Our simulation results show that the time-Reversibility theory helps to find up to 13.1% additional EDF-schedulable task sets on a multiprocessor platform.

Margaret Garin - One of the best experts on this subject based on the ideXlab platform.

  • in patients with severe asthma with eosinophilia in reslizumab clinical trials high peripheral blood eosinophil levels are associated with low fev1 Reversibility
    Allergy Asthma & Clinical Immunology, 2020
    Co-Authors: Christian J Virchow, Lisa Hickey, Evelyn Du, Margaret Garin
    Abstract:

    Background: A post hoc analysis of two randomized, placebo-controlled, Phase 3 trials of intravenous reslizumab, an anti-interleukin-5 (IL-5) biologic for severe eosinophilic asthma. Methods: Relationships between baseline blood eosinophil levels (EOS), forced expiratory volume in 1 s (FEV1) Reversibility to beta2-agonists and treatment outcomes were assessed. Results: Mean baseline FEV1 Reversibility was numerically lower among patients with high (>/= 400 cells/microL) versus low baseline EOS. Reslizumab produced clinically significant improvement in FEV1, exacerbation rates and patient-reported outcomes after 52 weeks, including in patients with high EOS and low FEV1 Reversibility ( /= 12% might exclude patients who would benefit from treatment with anti-IL-5 biologics.

  • In patients with severe asthma with eosinophilia in reslizumab clinical trials, high peripheral blood eosinophil levels are associated with low FEV1 Reversibility.
    Allergy asthma and clinical immunology : official journal of the Canadian Society of Allergy and Clinical Immunology, 2020
    Co-Authors: J Christian Virchow, Evelyn Du, Lisa Hickey, Margaret Garin
    Abstract:

    A post hoc analysis of two randomized, placebo-controlled, Phase 3 trials of intravenous reslizumab, an anti-interleukin-5 (IL-5) biologic for severe eosinophilic asthma. Relationships between baseline blood eosinophil levels (EOS), forced expiratory volume in 1 s (FEV1) Reversibility to β2-agonists and treatment outcomes were assessed. Mean baseline FEV1 Reversibility was numerically lower among patients with high (≥ 400 cells/µL) versus low baseline EOS. Reslizumab produced clinically significant improvement in FEV1, exacerbation rates and patient-reported outcomes after 52 weeks, including in patients with high EOS and low FEV1 Reversibility (≤ 14%) to β2-agonists at baseline. Clinical trial eligibility criteria stipulating minimum FEV1 Reversibility to β2-agonists of ≥ 12% might exclude patients who would benefit from treatment with anti-IL-5 biologics. © The Author(s) 2020.

Dennis S. Bernstein - One of the best experts on this subject based on the ideXlab platform.

  • Poincaré recurrence and output Reversibility in linear dynamical systems
    2012 IEEE 51st IEEE Conference on Decision and Control (CDC), 2012
    Co-Authors: Sergey G. Nersesov, Wassim M. Haddad, Dennis S. Bernstein
    Abstract:

    Reversibility of dynamical processes arises in many physical dynamical systems. For example, lossless Newtonian and Hamiltonian mechanical systems exhibit trajectories that can be obtained by time going forward and backward, providing an example of time symmetry that arises in natural sciences. Another example of such time symmetry is the phenomenon known as Poincaré recurrence wherein the dynamical system exhibits trajectories that return infinitely often to neighborhoods of their initial conditions. In this paper, we study output Reversibility in linear dynamical systems, that is, the backward recoverability of the system output while time is going forward. Specifically, we provide necessary and sufficient conditions for output Reversibility in terms of the spectrum of the system dynamics. In addition, we provide sufficient conditions for the absence of output Reversibility. Furthermore, we establish that no system trajectory can retrace its time history backwards with time going forward which is also natural in light of the uniqueness of solutions to linear dynamical systems. Finally, we draw connections between output Reversibility and Poincaré recurrence.

  • Poincaré recurrence and output Reversibility in linear dynamical systems
    2012 IEEE 51st IEEE Conference on Decision and Control (CDC), 2012
    Co-Authors: Sergey G. Nersesov, Wassim M. Haddad, Dennis S. Bernstein
    Abstract:

    Reversibility of dynamical processes arises in many physical dynamical systems. For example, lossless Newtonian and Hamiltonian mechanical systems exhibit trajectories that can be obtained by time going forward and backward, providing an example of time symmetry that arises in natural sciences. Another example of such time symmetry is the phenomenon known as Poincaré recurrence wherein the dynamical system exhibits trajectories that return infinitely often to neighborhoods of their initial conditions. In this paper, we study output Reversibility in linear dynamical systems, that is, the backward recoverability of the system output while time is going forward. Specifically, we provide necessary and sufficient conditions for output Reversibility in terms of the spectrum of the system dynamics. In addition, we provide sufficient conditions for the absence of output Reversibility. Furthermore, we establish that no system trajectory can retrace its time history backwards with time going forward which is also natural in light of the uniqueness of solutions to linear dynamical systems. Finally, we draw connections between output Reversibility and Poincaré recurrence.

Christian J Virchow - One of the best experts on this subject based on the ideXlab platform.

  • in patients with severe asthma with eosinophilia in reslizumab clinical trials high peripheral blood eosinophil levels are associated with low fev1 Reversibility
    Allergy Asthma & Clinical Immunology, 2020
    Co-Authors: Christian J Virchow, Lisa Hickey, Evelyn Du, Margaret Garin
    Abstract:

    Background: A post hoc analysis of two randomized, placebo-controlled, Phase 3 trials of intravenous reslizumab, an anti-interleukin-5 (IL-5) biologic for severe eosinophilic asthma. Methods: Relationships between baseline blood eosinophil levels (EOS), forced expiratory volume in 1 s (FEV1) Reversibility to beta2-agonists and treatment outcomes were assessed. Results: Mean baseline FEV1 Reversibility was numerically lower among patients with high (>/= 400 cells/microL) versus low baseline EOS. Reslizumab produced clinically significant improvement in FEV1, exacerbation rates and patient-reported outcomes after 52 weeks, including in patients with high EOS and low FEV1 Reversibility ( /= 12% might exclude patients who would benefit from treatment with anti-IL-5 biologics.

Sabina Rossi - One of the best experts on this subject based on the ideXlab platform.

  • On the Relations between Lumpability and Reversibility
    2014 IEEE 22nd International Symposium on Modelling, Analysis & Simulation of Computer and Telecommunication Systems, 2014
    Co-Authors: Andrea Marin, Sabina Rossi
    Abstract:

    In the literature devoted to the efficient solution of Continuous Time Markov Chains (CTMCs) the notions of lump ability and Reversibility have a central role. In the context of lump able Markov chains several definitions have been introduced: strong, exact and strict, just to mention a few of them. On the side of the analysis of reversible CTMCs the research community has shown great interest in the application of this notion with the aim of efficiently computing the stationary distribution of large models (e.g., obtained by composition of several processes). In this paper we show for the first time the relations between the above mentioned notions of lump ability and the concept of Reversibility. The major outcome of our research is proving a strong connection between the notion of strict lump ability and that of Reversibility.

  • AutoReversibility: Exploiting Symmetries in Markov Chains
    2013 IEEE 21st International Symposium on Modelling Analysis and Simulation of Computer and Telecommunication Systems, 2013
    Co-Authors: Andrea Marin, Sabina Rossi
    Abstract:

    The computation of the steady-state distribution of Continuous Time Markov Chains (CTMCs) may be a computationally hard problem when the number of states is very large. In order to overcome this problem, in the literature, several solutions have been proposed such as the reduction of the state space cardinality by lumping, the factorization based on product-form analysis and the application of the notion of Reversibility. In this paper we address this problem by introducing the notion of auto Reversibility which is defined as a symmetric co inductive relation which induces an equivalence relation among the chain's states. We show that all the states belonging to the same equivalence class share the same stationary probabilities and hence the computation of the steady-state distribution can be computationally more efficient. The definition of auto Reversibility takes inspiration by the Kolmogorov's criteria for reversible processes and hence requires to test a property on all the minimal cycles of the chain. We show that the notion of auto Reversibility is different from that of reversible processes and does not correspond to other state aggregation techniques such as lumping. Finally, we discuss the applicability of our results in the case of models defined in terms of a Markovian process Algebra such as the Performance Evaluation Process Algebra.