I'm interested in designing new distributed and parallel algorithms, the distributed processing of big data, achieving fault-tolerance in networks, and secure distributed computing in dynamic environments such as peer-to-peer networks and mobile ad-hoc networks.


Publications tagged with "Churn" (Show all)

  • Enabling Efficient and Robust Distributed Computation in Highly Dynamic Networks DOI
    John Augustine, Gopal Pandurangan, Peter Robinson, Scott Roche, Eli Upfal. 56th Annual IEEE Symposium on Foundations of Computer Science (FOCS 2015).
    Motivated by the need for designing efficient and robust fully-distributed computation in highly dynamic networks such as Peer-to-Peer (P2P) networks, we study distributed protocols for constructing and maintaining dynamic network topologies with good expansion properties. Our goal is to maintain a sparse (bounded degree) expander topology despite heavy churn (i.e., nodes joining and leaving the network continuously over time). We assume that the churn is controlled by an adversary that has complete knowledge and control of what nodes join and leave and at what time and has unlimited computational power, but is oblivious to the random choices made by the algorithm. Our main contribution is a randomized distributed protocol that guarantees with high probability the maintenance of a constant degree graph with high expansion even under continuous high adversarial churn. Our protocol can tolerate a churn rate of up to $O(n/\text{polylog}(n))$ per round (where $n$ is the stable network size). Our protocol is efficient, lightweight, and scalable, and it incurs only $O(\text{polylog}(n))$ overhead for topology maintenance: only polylogarithmic (in $n$) bits needs to be processed and sent by each node per round and any node's computation cost per round is also polylogarithmic. The given protocol is a fundamental ingredient that is needed for the design of efficient fully-distributed algorithms for solving fundamental distributed computing problems such as agreement, leader election, search, and storage in highly dynamic P2P networks and enables fast and scalable algorithms for these problems that can tolerate a large amount of churn.
  • Distributed Agreement in Dynamic Peer-to-Peer Networks PDF DOI
    John Augustine, Gopal Pandurangan, Peter Robinson, Eli Upfal. Journal of Computer and System Sciences, Elsevier. (JCSS).


I'm interested in parallel and distributed programming and related technologies such as software transactional memory. Below is a (non-comprehensive) list of software that I have written.
  • I extended Cabal, for using a "world" file to keep track of installed packages. (Now part of the main distribution.)
  • data dispersal: an implementation of an (m,n)-threshold information dispersal scheme that is space-optimal.
  • secret sharing: an implementation of a secret sharing scheme that provides information-theoretic security.
  • dice-entropy: a library that provides cryptographically secure dice rolls implemented by bit-efficient rejection sampling.
  • TSkipList: a data structure with range-query support for software transactional memory.
  • stm-io-hooks: An extension of Haskell's Software Transactional Memory (STM) monad with commit and retry IO hooks.
  • Mathgenealogy: Visualize your (academic) genealogy! A program for extracting data from the Mathematics Genealogy project.
  • In my master thesis I developed a system for automatically constructing events out of log files produced by various system programs. One of the core components of my work was a part-of-speech (POS) tagger, which assigns word classes (e.g. noun, verb) to the previously parsed tokens of the log file. To cope with noisy input data, I modeled the POS tagger as a hidden Markov model. I developed (and proved the correctness of) a variant of the maximum likelihood estimation algorithm for training the Markov model and smoothing the state transition distributions.


  • Conferences that I attended so far: PODC 2008 (Toronto, Canada); SSS 2008 (Detroit, USA); OPODIS 2009 (Nimes, France); ALGOSENSORS 2010 (Bordeaux, France); DISC 2010; (Boston, USA) IPDPS 2011 (Anchorage, USA); FOMC 2011 (San Jose, USA); SODA 2012 (Kyoto, Japan); SIROCCO 2012 (Reykjavik, Iceland); ICDCN 2013 (Mumbai, India); ICALP 2013 (Riga, Latvia); SPAA 2013 (Montreal, Canada); PODC 2013 (Montreal, Canada); Shonan Workshop (Shonan Village, Japan); DISC 2015 (Tokyo, Japan); ICDCN 2016 (Singapore); SPAA 2016 (Monterey, California); DISC 2016 (Paris, France).
  • Program committee membership: BGP 2017, ICDCN 2016, SPAA 2016, SIROCCO 2016, ICDCN 2015, SIROCCO 2014, FOMC 2014
  • DBLP entry.
  • Google Scholar profile.
  • Profile on StackExchange.