Category Archives: CS

Ali Ebnenasir is Co-author of Article in ACM Transactions on Computational Logic

Ali EbnenasirAli Ebnenasir (SAS/CS), professor of computer science, is co-author of the article, “On the verification of livelock-freedom and self-stabilization on parameterized rings,” published in the July 2019 issue of the journal ACM Transactions on Computational Logic. The article is co-authored by Alex Klinkhamer of Google.

Abstract: This article investigates the verification of livelock-freedom and self-stabilization on parameterized rings consisting of symmetric, constant space, deterministic, and self-disabling processes. The results of this article have a significant impact on several fields, including scalable distributed systems, resilient and self-* systems, and verification of parameterized systems. First, we identify necessary and sufficient local conditions for the existence of global livelocks in parameterized unidirectional rings with unbounded (but finite) number of processes under the interleaving semantics. Using a reduction from the periodic domino problem, we show that, in general, verifying livelock-freedom of parameterized unidirectional rings is undecidable (specifically, Π10-complete) even for constant space, deterministic, and self-disabling processes. This result implies that verifying self-stabilization for parameterized rings of self-disabling processes is also undecidable. We also show that verifying livelock-freedom and self-stabilization remain undecidable under (1) synchronous execution semantics, (2) the FIFO consistency model, and (3) any scheduling policy. We then present a new scope-based method for detecting and constructing livelocks in parameterized rings. The proposed semi-algorithm behind our scope-based verification is based on a novel paradigm for the detection of livelocks that totally circumvents state space exploration. Our experimental results on an implementation of the proposed semi-algorithm are very promising as we have found livelocks in parameterized rings in a few microseconds on a regular laptop. The results of this article have significant implications for scalable distributed systems with cyclic topologies.

Citation: Klinkhamer, A., & Ebnenasir, A. (2019). On the verification of livelock-freedom and self-stabilization on parameterized rings. ACM Transactions on Computational Logic, 20(3), 16:1-16:36. http://dx.doi.org/10.1145/3326456

MTU Digital Commons link: https://digitalcommons.mtu.edu/michigantech-p/146/

ACM link: https://dl.acm.org/citation.cfm?doid=3338853.3326456

Ali Ebnenasir is Co-Author of Publication in ACM Transactions on Computational Logic

Ali Ebnenasir

An article co-authored by Ali Ebnenasir (SAS/CS) and Alex Klinkhamer, “Verification of Livelock-Freedom and Self-Stabilization on Parameterized Rings,” was recently published in ACM Transactions on Computational Logic.

Abstract: This article investigates the verification of livelock-freedom and self-stabilization on parameterized rings consisting of symmetric, constant space, deterministic, and self-disabling processes. The results of this article have a significant impact on several fields, including scalable distributed systems, resilient and self-* systems, and verification of parameterized systems. First, we identify necessary and sufficient local conditions for the existence of global livelocks in parameterized unidirectional rings with unbounded (but finite) number of processes under the interleaving semantics. Using a reduction from the periodic domino problem, we show that, in general, verifying livelock-freedom of parameterized unidirectional rings is undecidable (specifically, Π10-complete) even for constant space, deterministic, and self-disabling processes. This result implies that verifying self-stabilization for parameterized rings of self-disabling processes is also undecidable. We also show that verifying livelock-freedom and self-stabilization remain undecidable under (1) synchronous execution semantics, (2) the FIFO consistency model, and (3) any scheduling policy. We then present a new scope-based method for detecting and constructing livelocks in parameterized rings. The proposed semi-algorithm behind our scope-based verification is based on a novel paradigm for the detection of livelocks that totally circumvents state space exploration. Our experimental results on an implementation of the proposed semi-algorithm are very promising as we have found livelocks in parameterized rings in a few microseconds on a regular laptop. The results of this article have significant implications for scalable distributed systems with cyclic topologies.

https://dl.acm.org/citation.cfm?id=3326456&dl=ACM&coll=DL

doi: 10.1145/3326456

Soner Onder To Present Invited Talk

Soner OnderDr. Soner Onder (CS, SAS) will present an invited talk titled “Program semantics meets architecture: What if we did not have branches?” at a workshop organized in honor of the 80th birthday of Prof. Yale Patt of University of Texas, Austin. Prof. Patt is a prominent researcher with decades of accomplishments in Computer Architecture.

The workshop, titled “Yale:80 in 2019, Pushing the Envelope of Computing for the Future,” will take place July 1-2, 2019, in Barcelona, Spain. The workshop is organized by Universitat Politècnica de Catalunya and Barcelona Supercomputing Center, and sponsored by the Ministry of Science, Innovation and Universities of Spain, among others.