DOCSLIB.ORG

On the Complexity of Synchronization Rati Gelashvili

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
On the Complexity of Synchronization Rati Gelashvili On the Complexity of Synchronization by Rati Gelashvili B.S., Swiss Federal Institute of Technology (2012) S.M., Massachusetts Institute of Technology (2014) Submitted to the Department of Electrical Engineering and Computer Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science and Engineering at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 2017 ○c Massachusetts Institute of Technology 2017. All rights reserved. Author................................................................ Department of Electrical Engineering and Computer Science May 19, 2017 Certified by. Nir Shavit Professor of Electrical Engineering and Computer Science Thesis Supervisor Accepted by . Leslie A. Kolodziejski Professor of Electrical Engineering and Computer Science Chair, Department Committee on Graduate Students 2 On the Complexity of Synchronization by Rati Gelashvili Submitted to the Department of Electrical Engineering and Computer Science on May 19, 2017, in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Computer Science and Engineering Abstract The field of distributed algorithms revolves around efficiently solving synchronization tasks, such as leader election and consensus. We make contributions towards a better understanding of the complexity of central tasks in standard distributed models. In the population protocols model, we demonstrate how to solve majority and leader election efficiently, in time O(log2 n), using O(log n) states per node, for n nodes. Central to our algorithms is a new leaderless phase clock technique. We also prove tight lower bounds on the state complexity of solving these tasks. In shared memory, we prove that any nondeterministic solo terminating consen- sus algorithm for anonymous processes has to use Ω(n) read-write registers. Then, we show how to solve n-process wait-free consensus by combining synchronization instructions that would be considered “weak” according to Herlihy’s consensus hier- archy. This collapses the hierarchy when instructions can be applied to the same memory location, as is the case in all existing multicore processors. We suggest an alternative hierarchy and provide a practical universal construction using only “weak” instructions, that performs as well as the Compare-and-Swap-based solution. Space complexity of solving k-set agreement is a problem that highlights important gaps in our understanding and state-of-the-art methods. No general lower bound better than 2 is known. We introduce a new technique based on an indirect black-box application of Sperner’s Lemma through an algorithmic reduction to the impossibility of wait-free k-set agreement. We design a simulation such that for any protocol Π either the simulating processes solve wait-free k-set agreement (impossible), or they simulate an execution of Π that uses many registers. Finally, time complexity of leader election is a long-standing open problem. We give an algorithm with O(log? k) time complexity in asynchronous message-passing system, for k participants. Thesis Supervisor: Nir Shavit Title: Professor of Electrical Engineering and Computer Science 3 4 Acknowledgments I would like to thank Professor Nir Shavit for supervision, an incredible support and for introducing me to the exciting field of concurrent algorithms. It is my privilege and pleasure to be a student of Nir who I respect and admire as a wonderful human being and a brilliant researcher and advisor, my true role model. In many ways interaction with Nir shaped me as a scientist, a friend and a world citizen. I want to thank Professor Faith Ellen - for thorough feedback, outstanding sup- port and encouragement. I am very much looking forward to the postdoc under her supervision. Special thanks to Professors James Aspnes and Aleksander Madry for their valu- able feedback and the very fact of serving on my thesis committee. This thesis is based on joints works with Dan Alistarh, Jim Aspnes, David Eisen- stat, Faith Ellen, Idit Keidar, Ron Rivest, Nir Shavit, Alexander (Sasha) Spiegelman, Adrian Vladu, Milan Vojnovic, Roger Wattenhofer, Leqi (Jimmy) Zhu. Razor-sharp discussions were part of these enjoyable intellectual journeys under which I learnt, grew, and matured as a scientist. I would like to specially thank Dan Alistarh for taking me under his wing as a young student, and Jimmy Zhu for the most productive, challenging and very pleasant collaborations. I would also like to thank Philipp Woelfel, Yoram Moses, Idit Keidar, Sasha Spiegelman, Faith Ellen, Jimmy Zhu, Dan Alistarh for hosting me as a visitor at various points during my PhD - you have been amazing hosts and inspiring presence! Family and friends from all around the world - without your support I would not have been where I am today! Friends in the Boston area with whom I spent past five years (including frosty winters). Among them I want to say special thanks to Guranda Darchidze, Ilya Razenshteyn, Shibani Santurkar, David Budden, Adrian Vladu, Mohsen Ghaffari, Jerry Li, Guatam 1 “G” Kamath, Mira Radeva, Mari Kobiashvili, Tornike Metreveli, Sasha Konstantinov, Achuta Kadambi, Merav Parter and Stephan Holzer. 1Gautam 5 A huge part of this experience has been internships. Thus, I would like to thank Milan Vojnovic, Dan Alistarh, David Amenhauser, Debabrata Banerjee, Bogdan Munteanu, Diwaker Gupta, Mirjam Wattenhofer and Kriti Puniyani for providing outstanding personal and work environment. I am very thankful to MIT Department of Computer Science and Electrical En- gineering for providing the funding for my education and research. Lastly, I want to mention Soso (Sensei) Dzmanashvili for unconditional support and extracurricular inspiration. 6 Contents 1 Introduction 13 1.1 On Population Protocols . 14 1.1.1 Leader Election and Majority . 16 1.1.2 Summary . 19 1.1.3 Chapter Outline . 19 1.2 On Shared Memory . 22 1.2.1 Complexity-Based Hierarchy . 22 1.2.2 Towards Reduced Instruction Sets for Synchronization . 24 1.2.3 Anonymous Space Lower Bound . 25 1.2.4 k-Set Agreement . 27 1.2.5 Chapter Outline . 30 1.3 On Message Passing . 32 2 Population Protocols 35 2.1 Model . 35 2.2 Leader-Minion Algorithm . 40 2.2.1 Analysis . 42 2.3 Leaderless Phase Clock . 48 2.3.1 Analysis . 49 2.4 Phased Majority Algorithm . 51 2.4.1 Analysis . 55 2.5 Synthetic Coin Flips . 66 2.5.1 Analysis . 66 7 2.5.2 Approximate Counting . 69 2.6 Phased Leader Election . 69 2.6.1 Analysis . 71 2.7 Lower Bounds . 72 2.7.1 Technical Tools . 72 2.7.2 Output-Dominant Majority . 78 2.7.3 General Lower Bound . 84 3 Shared Memory 97 3.1 Anonymous Space Lower Bound . 97 3.1.1 Definitions and Notation . 98 3.1.2 A Square-Root Lower Bound . 100 3.1.3 Linear Lower Bound . 104 3.2 The Space Hierarchy . 117 3.2.1 Model . 117 3.2.2 Arithmetic Instructions . 118 3.2.3 Increment . 121 3.2.4 Buffers . 123 3.2.5 Multiple Assignment . 132 3.3 Universality using “Weak” Instructions . 140 3.3.1 Algorithm . 142 3.4 Enter the Simulation: k-Set Agreement . 145 3.4.1 Model . 145 3.4.2 Local Argument . 146 3.4.3 Global Argument . 151 4 Message Passing 163 4.1 Definitions and Notation . 163 4.2 Leader Election Algorithm . 166 4.2.1 The PoisonPill Technique . 166 4.2.2 Heterogeneous PoisonPill . 167 8 4.2.3 Final construction . 170 5 Conclusions 179 9 10 List of Figures 1-1 Summary of results on Majority and Leader Election. 20 2-1 The state update rules for the LM algorithm. 41 2-2 Pseudocode for the phased majority algorithm, part 1/2 . 95 2-3 Pseudocode for the phased majority algorithm, part 2/2 . 96 3-1 Proof of Lemma 3.1.10, Case 1 . 112 3-2 Proof of Lemma 3.1.10, Case 2 . 114 3-3 Illustration of Case 2 in History object emulation . 126 3-4 Element of A. ................................ 142 3-5 Pseudocode for the Implementation of a 1-Augmented Snapshot Object 154 4-1 PoisonPill Technique . 166 4-2 Heterogeneous PoisonPill . 168 4-3 PreRound procedure . 171 4-4 Doorway procedure . 172 4-5 Leader election algorithm . 172 11 12 Chapter 1 Introduction To solve a problem in a distributed fashion, nodes peforming parts of the computa- tion need to synchronize with each other. The common synchronization requirements are often abstracted and captured by synchronization tasks. Examples of important synchronization tasks include consensus (agreement) [LSP82, PSL80], leader elec- tion (test-and-set) [AGTV92], majority [Tho79], mutual exclusion [Dij65], renam- ing [ABND+90], task allocation (do-all) [KS92] and timestamps [Lam78]. These tasks are usually considered in two classical models for distributed com- putation: asynchronous shared memory and asynchronous message-passing [Lyn96]. Additionally, population protocols [AAD+06] are a popular model of distributed com- puting, in which randomly-interacting agents with little computational power coop- erate to jointly perform complex computation. In all these models, randomization plays a critical role in solving synchronization tasks. In population protocols, interactions happen according to a randomized sched- uler. In the classical models, celebrated impossibility results of [FLP85, HS99] limit the power of deterministic distributed computation. Fortunately, relaxing the task specifications to allow for randomization [BO83] (and in particular, probabilistic ter- mination) has proved a very useful tool for circumventing fundamental impossibilities, and for obtaining efficient algorithms. In each model, there are two standard complexity measures. Time complexity, defined appropriately, can be formulated in all three models. In population protocols, 13 the other (more important) measure is state complexity of the agents. In asynchronous shared memory, space complexity denotes the number of shared memory locations that can be concurrently accessed by processors. Such locations have historically also been called registers. In asynchronous message-passing, the other natural measure is message complexity of an algorithm.
Load more

Recommended publications
  • ACM SIGACT News Distributed Computing Column 28
    ACM SIGACT News Distributed Computing Column 28 Idit Keidar Dept. of Electrical Engineering, Technion Haifa, 32000, Israel [email protected] Sergio Rajsbaum, who edited this column for seven years and established it as a relevant and popular venue, is stepping down. This issue is my first step in the big shoes he vacated. I would like to take this opportunity to thank Sergio for providing us with seven years’ worth of interesting columns. In producing these columns, Sergio has enjoyed the support of the community at-large and obtained material from many authors, who greatly contributed to the column’s success. I hope to enjoy a similar level of support; I warmly welcome your feedback and suggestions for material to include in this column! The main two conferences in the area of principles of distributed computing, PODC and DISC, took place this summer. This issue is centered around these conferences, and more broadly, distributed computing research as reflected therein, ranging from reviews of this year’s instantiations, through influential papers in past instantiations, to examining PODC’s place within the realm of computer science. I begin with a short review of PODC’07, and highlight some “hot” trends that have taken root in PODC, as reflected in this year’s program. Some of the forthcoming columns will be dedicated to these up-and- coming research topics. This is followed by a review of this year’s DISC, by Edward (Eddie) Bortnikov. For some perspective on long-running trends in the field, I next include the announcement of this year’s Edsger W.
    [Show full text]
  • A Study on Asynchronous Randomized Consensus Title Algorithms for Byzantine Fault Tolerant Replication
    A Study on Asynchronous Randomized Consensus Title Algorithms for Byzantine Fault Tolerant Replication Author(s) 中村, 純哉 Citation Issue Date Text Version ETD URL https://doi.org/10.18910/34568 DOI 10.18910/34568 rights Note Osaka University Knowledge Archive : OUKA https://ir.library.osaka-u.ac.jp/ Osaka University A Study on Asynchronous Randomized Consensus Algorithms for Byzantine Fault Tolerant Replication Submitted to Graduate School of Information Science and Technology Osaka University January 2014 Junya NAKAMURA iii List of Major Publications Journal Papers 1. Junya Nakamura, Tadashi Araragi, Toshimitsu Masuzawa, and Shigeru Masuyama, \A method of parallelizing consensuses for accelerating byzantine fault tolerance," IEICE Trans- actions on Information and Systems, vol. E97-D, no. 1, 2014. (to appear). 2. Junya Nakamura, Tadashi Araragi, Shigeru Masuyama, and Toshimitsu Masuzawa, “Effi- cient randomized byzantine fault-tolerant replication based on special valued coin tossing," IEICE Transactions on Information and Systems, vol. E97-D, no. 2, 2014. (to appear). Conference Papers 3. Junya Nakamura, Tadashi Araragi, and Shigeru Masuyama, \Asynchronous byzantine request- set agreement algorithm for replication," in Proceedings of the 1st AAAC Annual Meeting, p. 35, 2008. 4. Junya Nakamura, Tadashi Araragi, and Shigeru Masuyama, \Acceleration of byzantine fault tolerance by parallelizing consensuses," in Proceedings of the 10th International Conference on Parallel and Distributed Computing, Applications and Technologies, PDCAT '09, pp. 80{ 87, Dec. 2009. Technical Reports 5. Junya Nakamura, Tadashi Araragi, and Shigeru Masuyama, \Byzantine agreement on the order of processing received requests is solvable deterministically in asynchronous systems," in IEICE Technical Report, vol. 106 of COMP2006-35, pp. 33{40, Oct.
    [Show full text]
  • Topology in Distributed Computing
    Die approbierte Originalversion dieser Diplom-/Masterarbeit ist an der Hauptbibliothek der Technischen Universität Wien aufgestellt (http://www.ub.tuwien.ac.at). The approved original version of this diploma or master thesis is available at the main library of the Vienna University of Technology (http://www.ub.tuwien.ac.at/englweb/). Topology in Distributed Computing DIPLOMARBEIT zur Erlangung des akademischen Grades Diplom-Ingenieur im Rahmen des Studiums Technische Informatik ausgeführt von Thomas Nowak Matrikelnummer 0425201 an der Fakultät für Informatik der Technischen Universität Wien Betreuer: Univ.Prof. Dr. Ulrich Schmid Wien, 18.03.2010 _______________________ ______________________ (Unterschrift Verfasser) (Unterschrift Betreuer) Technische Universität Wien A-1040 Wien Karlsplatz 13 Tel. +43/(0)1/58801-0 http://www.tuwien.ac.at Erklärung Thomas Nowak Rechte Wienzeile 73/23 1050 Wien Hiermit erkläre ich, dass ich diese Arbeit selbstständig verfasst habe, dass ich die verwendeten Quellen und Hilfsmittel vollständig angegeben habe und dass ich die Stellen der Arbeit – einschließlich Tabellen, Karten und Abbildungen –, die anderen Werken oder dem Internet im Wortlaut oder dem Sinn nach entnommen sind, auf jeden Fall unter Angabe der Quelle als Entlehnung kenntlich gemacht habe. Wien, 18.03.2010 ______________________ (Unterschrift) Abstract Topology is the general mathematical theory of convergence. Distributed com- puting is the formal investigation of communicating concurrent processes. We explore applications of topology to distributed computing in two directions: (1) Point-set topology and (2) algebraic topology. We use the former to study the topological structure of infinite execution trees. This enables us to unify a number of impossibility proofs, in particular, the impossibility of distributed consensus — the task of all processes in a system agreeing on a single value — in various (close to) asynchronous systems with crash failures.
    [Show full text]
  • Auto-Stabilisation : Solution Elégante Pour Lutter Contre Les Fautes Sylvie
    Auto-stabilisation : Solution Elégante pour Lutter contre Les Fautes Sylvie Delaët Rapport scientifique présenté en vue de l’obtention de l’Habilitation à Diriger les Recherches. Soutenu le 8 novembre 2013 devant le jury composé de : Alain Denise, Professeur, Université Paris Sud, France Shlomi Dolev, Professeur, Ben Gurion University of the Negev, Israël Pierre Fraigniaud, Directeur de recherche CNRS, France Ted Herman, Professeur, University of Iowa, Etats Unis d’Amérique Nicolas Thiéry, Professeur, l’Université Paris Sud, France Franck Petit, Professeur, Université Paris Pierre et Marie Curie, France Après avis des rapporteurs : Ted Herman, Professeur, University of Iowa, Etats Unis d’Amérique Rachid Guerraoui, Professeur, Ecole Polytechnique Fédérale de Lausanne, Suisse Franck Petit, Université Paris Pierre et Marie Curie, France ii Sommaire Remerciements iii 1 Ma vision de ce document 1 1.1 Organisation du document . .1 2 Un peu de cuisine(s) 3 2.1 L'auberge espagnole de l'algorithmique r´epartie. .4 2.2 Exemples de probl`emes`ar´esoudreet quelques solutions . .8 3 Comprendre le monde 15 3.1 Comprendre l'auto-stabilisation . 15 3.2 Comprendre l'algorithmique r´epartie . 30 3.3 Comprendre mes contributions . 34 4 Construire l'avenir 43 4.1 Perspectives d'am´eliorationdes techniques . 43 4.2 Perspective d'ouverture `ala diff´erence . 45 4.3 Perspective de diffusion plus large . 47 4.4 Perspective de l'ordinateur auto-stabilisant . 48 A Agrafage 51 A.1 Cerner les probl`emes . 51 A.2 D´emasquerles planqu´es . 59 A.3 Recenser les pr´esents . 67 A.4 Obtenir l'auto-stabilisation gratuitement .
    [Show full text]
  • Why Extension-Based Proofs Fail
    Why Extension-Based Proofs Fail Dan Alistarh James Aspnes Faith Ellen IST Austria Yale University of Toronto [email protected] [email protected] [email protected] Rati Gelashvili Leqi Zhu University of Toronto University of Michigan [email protected] [email protected] August 2, 2020 Abstract We introduce extension-based proofs, a class of impossibility proofs that includes valency arguments. They are modelled as an interaction between a prover and a protocol. Using proofs based on combinatorial topology, it has been shown that it is impossible to deterministically solve k-set agreement among n > k 2 processes in a wait-free manner in certain asynchronous models. However, it was unknown whether≥ proofs based on simpler techniques were possible. We show that this impossibility result cannot be obtained for one of these models by an extension- based proof and, hence, extension-based proofs are limited in power. 1 Introduction One of the most well-known results in the theory of distributed computing, due to Fischer, Lynch, and Paterson [FLP85], is that there is no deterministic, wait-free protocol solving consensus among n 2 processes in an asynchronous message passing system, even if at most one process may ≥ crash. Their result has been extended to asynchronous shared memory systems where processes communicate by reading from and writing to shared registers [Abr88, CIL87, Her91, LAA87]. Moses and Rajsbaum [MR02] gave a unified framework for proving the impossibility of consensus in a number of different systems. Chaudhuri [Cha93] conjectured that the impossibility of consensus could be generalized to the k-set agreement problem.
    [Show full text]
  • On the Asynchronous Computability Theorem
    On the Asynchronous Computability Theorem Rachid Guerraoui Petr Kouznetsov Bastian Pochon Distributed Programming Laboratory EPFL GETCO 2004 2/23 Characterization T 1 of wait-free computable decision tasks [Herlihy and Shavit, 1993, 1994] • representing decision tasks through simplicial complexes and simplicial maps • a task is solvable iff the corresponding complexes satisfy a topological property T 1 • long-standing impossibility results: set agreement [BG93, SZ93] and (n, 2n)-renaming GETCO 2004 3/23 [Borowsky and Gafni, 1997]: a “stronger” geometric property T 2 • a “simpler” algorithmic proof of T 2 • the equivalence of the properties: T 1 = T 2 (through proving a geometric result with a distributed algorithm) Why “stronger” and “simpler” ? What is the distributed algorithm? GETCO 2004 4/23 Decision task T = (I, O, ∆) [HS93] • I — chromatic input complex (a set of possible input simplexes) • O — chromatic output complex (a set of possible output simplexes) • ∆ ⊆ I × O — task specification (a color-preserving map that carries every input simplex to a set of output simplexes) GETCO 2004 5/23 Wait-free protocols Every process starts with an input value, executes a number of writes and reads of the shared memory, and finishes with an output value (applies a decision map to its final state). A protocol solves a task T = (I, O, ∆) if it satisfies the task specification: for any input simplex S ∈ I, any resulting output simplex O ∈ ∆(S). A protocol wait-free if every process finishes in a bounded number of its own steps, no matter how other processes behave. GETCO 2004 6/23 Herlihy and Shavit’s criterion [HS94] Theorem 1.
    [Show full text]
  • Population Protocols: Expressiveness, Succinctness and Automatic Verification
    Fakultat¨ fur¨ Informatik Technische Universitat¨ Munchen¨ Population Protocols: Expressiveness, Succinctness and Automatic Verification. Stefan Jaax Vollst¨andigerAbdruck der von der Fakult¨atf¨urInformatik der Technischen Universit¨at M¨unchen zur Erlangung des akademischen Grades eines Doktor der Naturwissenschaften (Dr. rer. nat.) genehmigten Dissertation. Vorsitzender: Prof. Dr. Helmut Seidl Pr¨ufendeder Dissertation: 1. Prof. Dr. Francisco Javier Esparza Estaun 2. Prof. Rupak Majumdar, Ph.D., Technische Universit¨atKaiserslautern Die Dissertation wurde am 03.03.2020 bei der Technischen Universit¨atM¨unchen eingereicht und durch die Fakult¨atf¨urInformatik am 04.06.2020 angenommen. Abstract Population protocols (Angluin et al., PODC, 2004) are a model of distributed computa- tion in which identical, finite-state, passively mobile agents interact in pairs to achieve a common goal. In the basic model of population protocols, agents compute number predicates by reaching a stable consensus. It is well known that population protocols compute precisely the semilinear predicates, or, equivalently, the predicates definable in Presburger arithmetic, the first-order theory of the natural numbers equipped with addition and the standard linear order. This thesis investigates three fundamental questions of the theory of population pro- tocols: Space complexity, verification complexity, and expressiveness of reasonable ex- tensions. Space Complexity. We show that every quantifier-free Presburger predicate ' aug- mented with remainder predicates is computable by a population protocol with poly(j'j) states, where j'j denotes the size of ' in binary encoding. Further, the protocol can be constructed in polynomial time. This is a major improvement to the previously known construction, which requires 2poly(j'j) states. As a special case, we consider predicates of the form 'c(x) = x ≥ c, where c is a positive integer constant.
    [Show full text]
  • Population Protocols Are Fast
    Population Protocols Are Fast Adrian Kosowski1 and Przemysław Uznanski´ 2 1Inria Paris, France 2 ETH Zürich, Switzerland Abstract A population protocol describes a set of state change rules for a population of n indistinguish- able finite-state agents (automata), undergoing random pairwise interactions. Within this very basic framework, it is possible to resolve a number of fundamental tasks in distributed computing, includ- ing: leader election, aggregate and threshold functions on the population, such as majority compu- tation, and plurality consensus. For the first time, we show that solutions to all of these problems can be obtained quickly using finite-state protocols. For any input, the designed finite-state proto- cols converge under a fair random scheduler to an output which is correct with high probability in expected O(poly log n) parallel time. In the same setting, we also show protocols which always reach a valid solution, in expected parallel time O(nε), where the number of states of the interacting automata depends only on the choice of ε > 0. The stated time bounds hold for any semi-linear predicate computable in the population protocol framework. The key ingredient of our result is the decentralized design of a hierarchy of phase-clocks, which tick at different rates, with the rates of adjacent clocks separated by a factor of Θ(log n). The construction of this clock hierarchy relies on a new protocol composition technique, combined with an adapted analysis of a self-organizing process of oscillatory dynamics. This clock hierarchy is used to provide nested synchronization primitives, which allow us to view the population in a global manner and design protocols using a high-level imperative programming language with a (limited) capacity for loops and branching instructions.
    [Show full text]
  • On the Space Complexity of Colourless Tasks by Leqi Zhu A
    On the Space Complexity of Colourless Tasks by Leqi Zhu A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Graduate Department of Computer Science University of Toronto c Copyright 2019 by Leqi Zhu Abstract On the Space Complexity of Colourless Tasks Leqi Zhu Doctor of Philosophy Graduate Department of Computer Science University of Toronto 2019 In this thesis, we prove lower bounds on the number of registers needed to solve colourless tasks in asynchronous shared memory systems. Many fundamental synchronization tasks, such as consensus, k-set agreement, and -approximate agreement, are colourless. We show that it is possible to transform any nondeterministic solo-terminating algorithm (including any randomized wait-free algorithm) into an obstruction-free algorithm that uses the same number of registers. This result extends to algorithms using any finite number of deterministic objects that support read operations. Hence, we can focus on proving lower bounds for obstruction-free algorithms. We prove a tight lower bound on the number of registers needed to solve obstruction-free consensus. We also prove the first non-constant lower bounds on the number of registers needed to solve obstruction- free k-set agreement and obstruction-free -approximate agreement. The bound for k-set agreement is asymptotically tight when k is a constant and the bound for -approximate agreement is asymptotically tight when is sufficiently small. To prove these bounds, we introduce a new technique, revisionist simulations. This technique allows us to prove a general theorem that yields lower bounds on the number of registers needed to solve any colourless task in an obstruction-free manner.
    [Show full text]
  • ISBN # 1-60132-514-2; American Council on Science & Education / CSCE 2021
    ISBN # 1-60132-514-2; American Council on Science & Education / CSCE 2021 CSCI 2021 BOOK of ABSTRACTS The 2021 World Congress in Computer Science, Computer Engineering, and Applied Computing CSCE 2021 https://www.american-cse.org/csce2021/ July 26-29, 2021 Luxor Hotel (MGM Property), 3900 Las Vegas Blvd. South, Las Vegas, 89109, USA Table of Contents Keynote Addresses .................................................................................................................... 2 Int'l Conf. on Applied Cognitive Computing (ACC) ...................................................................... 3 Int'l Conf. on Bioinformatics & Computational Biology (BIOCOMP) ............................................ 6 Int'l Conf. on Biomedical Engineering & Sciences (BIOENG) ................................................... 12 Int'l Conf. on Scientific Computing (CSC) .................................................................................. 14 SESSION: Military & Defense Modeling and Simulation ............................................................ 27 Int'l Conf. on e-Learning, e-Business, EIS & e-Government (EEE) ............................................ 28 SESSION: Agile IT Service Practices for the cloud ................................................................... 34 Int'l Conf. on Embedded Systems, CPS & Applications (ESCS) ................................................ 37 Int'l Conf. on Foundations of Computer Science (FCS) ............................................................. 39 Int'l Conf. on Frontiers
    [Show full text]
  • K-Set Agreement Bounds in Round-Based Models Through Combinatorial Topology Adam Shimi, Armando Castañeda
    K-set agreement bounds in round-based models through combinatorial topology Adam Shimi, Armando Castañeda To cite this version: Adam Shimi, Armando Castañeda. K-set agreement bounds in round-based models through combina- torial topology. 39th ACM Symposium on Principles of Distributed Computing (PODC 2020), Aug 2020, Salerno, Italy. pp.395-404. hal-02950742 HAL Id: hal-02950742 https://hal.archives-ouvertes.fr/hal-02950742 Submitted on 28 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Open Archive Toulouse Archive Ouverte OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible This is an author’s version published in: http://oatao.univ-toulouse.fr/26404 Official URL https://doi.org/10.1145/3382734.3405752 To cite this version: Shimi, Adam and Castañeda, Armando K-set agreement bounds in round-based models through combinatorial topology. (2020) In: 39th ACM Symposium on Principles of Distributed Computing (PODC 2020), 3 August 2020 - 7 August 2020 (Salerno,
    [Show full text]
  • Versatility and Efficiency in Self-Stabilizing Distributed Systems
    Versatility and Efficiency in Self-Stabilizing Distributed Systems Stéphane Devismes To cite this version: Stéphane Devismes. Versatility and Efficiency in Self-Stabilizing Distributed Systems. Distributed, Parallel, and Cluster Computing [cs.DC]. Université Grenoble Alpes, 2020. tel-03080444v4 HAL Id: tel-03080444 https://hal.archives-ouvertes.fr/tel-03080444v4 Submitted on 21 Sep 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. HABILITATION À DIRIGER DES RECHERCHES Spécialité : Informatique Arrêté ministériel : 23 Novembre 1988 Présentée par Stéphane Devismes Habilitation préparée au sein du laboratoire VERIMAG et de l’École Doctorale Mathématiques, Sciences et Technologies de l’Information, Informatique Versatility and Efficiency in Self-Stabilizing Distributed Systems Généralité et Efficacité dans les Systèmes Distribués Autostabilisants Habilitation soutenue publiquement le 17 décembre 2020, devant le jury composé de : Denis TRYSTRAM Professeur, Grenoble INP, Président Toshimitsu MASUZAWA Professeur, Osaka University, Rapporteur Achour MOSTÉFAOUI
    [Show full text]