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  • Day: August 7, 2019

    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


    Saeid Nooshabadi is Co-author of Article in Journal of Parallel and Distributed Computing

    Saeid Nooshabadi

    Saeid Nooshabadi (SAS/ECE), professor of electrical and computer engineering, is co-author of the article, “High-dimensional image descriptor matching using highly parallel KD-tree construction and approximate nearest neighbor search,” to be published in  the October 2019 issue of the Journal of Parallel and Distributed Computing, which is published by Elsevier. The article is co-authored by Michigan Tech Computer Science department doctoral candidate Linjia Hu.

    Abstract: To overcome the high computational cost associated with the high-dimensional digital image descriptor matching, this paper presents a set of integrated parallel algorithms for the construction of K-dimensional tree (KD-tree) and P approximate nearest neighbor search (P-ANNS) on the modern massively parallel architectures (MPA). To improve the runtime performance of the P-ANNS, we propose an efficient sliding window for a parallel buffered P-ANNS on KD-tree to mitigate the high cost of global memory accesses. When applied to high dimensional real-world image descriptor datasets, the proposed KD-tree construction and the buffered P-ANNS algorithms are of comparable matching quality to the traditional sequential counterparts on CPU, while outperforming their serial CPU counterparts by speedup factors of up to 17 and 163, respectively. The algorithms are also studied for the performance impact factors to obtain the optimal runtime configurations for various datasets. Moreover, we verify the features of the parallel algorithms on typical 3D image matching scenarios. With the classical local image descriptor signature of histograms of orientations (SHOT) datasets, the parallel KD-tree construction and image descriptor matching can achieve up to 11 and 138-fold speedups, respectively.

    Citation: Hu, L., & Nooshabadi, S. (2019). High-dimensional image descriptor matching using highly parallel KD-tree construction and approximate nearest neighbor search. Journal of Parallel and Distributed Computing, 132, 127-140. http://dx.doi.org/10.1016/j.jpdc.2019.06.003

    MTU Digital Commons link: https://digitalcommons.mtu.edu/michigantech-p/145/

    Elsevier link: https://www.sciencedirect.com/science/article/pii/S0743731519304319?via%3Dihub


    Zhenlin Wang is Co-Author of Article in Parallel Programming Journal

    Zhenlin Wang (SAS), professor of computer science, is co-author of the article, “Lightweight and accurate memory allocation in key-value cache,” published in the June 2019 issue of the International Journal of Parallel Programming, which is published by Springer.

    Abstract: The use of key-value caches in modern web servers is becoming more and more ubiquitous. Representatively, Memcached as a widely used key-value cache system, originally intended for speeding up dynamic web applications by alleviating database load. One of the key factors affecting the performance of Memcached is the memory allocation among different item classes. How to obtain the most efficient partitioning scheme with low time and space consumption is a focus of attention. In this paper, we propose a lightweight and accurate memory allocation scheme in Memcached, by sampling access patterns, analyzing data locality, and reassigning the memory space. One early study on optimizing memory allocation is LAMA, which uses footprint-based MRC to optimize memory allocation in Memcached. However, LAMA does not model deletion operations in Memcached and its spatial overhead is quite large. We propose a method that consumes only 3% of LAMA space and can handle read, write and deletion operations. Moreover, evaluation results show that the average stable-state miss ratio is reduced by 15.0% and the average stable-state response time is reduced by 12.3% when comparing our method to LAMA.

    Citation: Pan, C., Zhou, L., Luo, Y., Wang, X., & Wang, Z. (2019). Lightweight and accurate memory allocation in key-value cache. International Journal of Parallel Programming, 47(3), 451-466.http://dx.doi.org/10.1007/s10766-018-0616-4

    Digital Commons link: https://digitalcommons.mtu.edu/michigantech-p/144/

    Springer link: https://link.springer.com/article/10.1007%2Fs10766-018-0616-4