2 Search Results for "Kulkarni, Sandeep S."

Document
DOI: 10.4230/LIPIcs.OPODIS.2015.23
Ensuring Average Recovery with Adversarial Scheduler

Authors: Jingshu Chen, Mohammad Roohitavaf, and Sandeep S. Kulkarni

Published in: LIPIcs, Volume 46, 19th International Conference on Principles of Distributed Systems (OPODIS 2015)

Abstract
In this paper, we focus on revising a given program so that the average recovery time in the presence of an adversarial scheduler is bounded by a given threshold lambda. Specifically, we consider the scenario where the fault (or other unexpected action) perturbs the program to a state that is outside its set of legitimate states. Starting from this state, the program executes its actions/transitions to recover to legitimate states. However, the adversarial scheduler can force the program to reach one illegitimate state that requires a longer recovery time. To ensure that the average recovery time is less than lambda, we need to remove certain transitions/behaviors. We show that achieving this average response time while removing minimum transitions is NP-hard. In other words, there is a tradeoff between the time taken to synthesize the program and the transitions preserved to reduce the average convergence time. We present six different heuristics and evaluate this tradeoff with case studies. Finally, we note that the average convergence time considered here requires formalization of hyperproperties. Hence, this work also demonstrates feasibility of adding (certain) hyperproperties to an existing program.
Cite as

Jingshu Chen, Mohammad Roohitavaf, and Sandeep S. Kulkarni. Ensuring Average Recovery with Adversarial Scheduler. In 19th International Conference on Principles of Distributed Systems (OPODIS 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 46, pp. 23:1-23:18, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{chen_et_al:LIPIcs.OPODIS.2015.23,
  author =	{Chen, Jingshu and Roohitavaf, Mohammad and Kulkarni, Sandeep S.},
  title =	{{Ensuring Average Recovery with Adversarial Scheduler}},
  booktitle =	{19th International Conference on Principles of Distributed Systems (OPODIS 2015)},
  pages =	{23:1--23:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-98-9},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{46},
  editor =	{Anceaume, Emmanuelle and Cachin, Christian and Potop-Butucaru, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2015.23},
  URN =		{urn:nbn:de:0030-drops-65907},
  doi =		{10.4230/LIPIcs.OPODIS.2015.23},
  annote =	{Keywords: Average Recovery Time, Hyper-liveness, Program Repair}
}
Document
DOI: 10.4230/LIPIcs.OPODIS.2015.34
Analysis of Bounds on Hybrid Vector Clocks

Authors: Sorrachai Yingchareonthawornchai, Sandeep S. Kulkarni, and Murat Demirbas

Published in: LIPIcs, Volume 46, 19th International Conference on Principles of Distributed Systems (OPODIS 2015)

Abstract
Hybrid vector clocks (HVC) implement vector clocks (VC) in a space-efficient manner by exploiting the availability of loosely-synchronized physical clocks at each node. In this paper, we develop a model for determining the bounds on the size of HVC. Our model uses four parameters, epsilon: uncertainty window, delta: minimum message delay, alpha: communication frequency and n: number of nodes in the system. We derive the size of HVC in terms of a differential equation, and show that the size predicted by our model is almost identical to the results obtained by simulation. We also identify closed form solutions that provide tight lower and upper bounds for useful special cases. Our model and simulations show the HVC size is a sigmoid function with respect to increasing epsilon; it has a slow start but it grows exponentially after a phase transition. We present equations to identify the phase transition point and show that for many practical applications and deployment environments, the size of HVC remains only as a couple entries and substantially less than n. We also find that, in a model with random unicast message transmissions, increasing n actually helps for reducing HVC size.
Cite as

Sorrachai Yingchareonthawornchai, Sandeep S. Kulkarni, and Murat Demirbas. Analysis of Bounds on Hybrid Vector Clocks. In 19th International Conference on Principles of Distributed Systems (OPODIS 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 46, pp. 34:1-34:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2016)

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@InProceedings{yingchareonthawornchai_et_al:LIPIcs.OPODIS.2015.34,
  author =	{Yingchareonthawornchai, Sorrachai and Kulkarni, Sandeep S. and Demirbas, Murat},
  title =	{{Analysis of Bounds on Hybrid Vector Clocks}},
  booktitle =	{19th International Conference on Principles of Distributed Systems (OPODIS 2015)},
  pages =	{34:1--34:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-98-9},
  ISSN =	{1868-8969},
  year =	{2016},
  volume =	{46},
  editor =	{Anceaume, Emmanuelle and Cachin, Christian and Potop-Butucaru, Maria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops-dev.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2015.34},
  URN =		{urn:nbn:de:0030-drops-66771},
  doi =		{10.4230/LIPIcs.OPODIS.2015.34},
  annote =	{Keywords: Vector Clocks, Physical Clocks, Large Scale Systems}
}
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