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Simpler Specifications and Easier Proofs of Distributed Algorithms Using History Variables

  • Saksham Chand
  • Yanhong A. Liu
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 10811)

Abstract

This paper studies specifications and proofs of distributed algorithms when only message history variables are used, using Basic Paxos and Multi-Paxos for distributed consensus as precise case studies. We show that not using and maintaining other state variables yields simpler specifications that are more declarative and easier to understand. It also allows easier proofs to be developed by needing fewer invariants and facilitating proof derivations. Furthermore, the proofs are mechanically checked more efficiently.

We show that specifications in TLA+ and proofs in TLA+ Proof System (TLAPS) are reduced by 25% and 27%, respectively, for Basic Paxos, and 46% (from about 100 lines to about 50 lines) and 48% (from about 1000 lines to about 500 lines), respectively, for Multi-Paxos. Overall we need 54% fewer manually written invariants and our proofs have 46% fewer obligations. Our proof for Basic Paxos takes 26% less time than Lamport et al.’s for TLAPS to check, and our proofs for Multi-Paxos are checked by TLAPS within 1.5 min whereas prior proofs for Multi-Paxos fail to be checked in the new version of TLAPS.

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Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Stony Brook UniversityStony BrookUSA

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