Time-adaptive algorithms for synchronization

Rajeev Alur, Hagit Attiya, Gadi Taubenfeld

Research output: Contribution to journalArticlepeer-review


We consider concurrent systems in which there is an unknown upper bound on memory access time. Such a model is inherently different from the asynchronous model, where no such bound exists, and also from timing-based models, where such a bound exists and is known a priori. The appeal of our model lies in the fact that while it abstracts from implementation details, it is a better approximation of real concurrent systems than the asynchronous model. Furthermore, it is stronger than the asynchronous model, enabling us to design algorithms for problems that are unsolvable in the asynchronous model. Two basic synchronization problems, consensus and mutual exclusion, are investigated in a shared-memory environment that supports atomic read/write registers. We show that Θ(Δlog Δ/log log Δ) is an upper and lower bound on the time complexity of consensus, where Δ is the (unknown) upper bound on memory access time. For the mutual exclusion problem, we design an efficient algorithm that takes advantage of the fact that some upper bound on memory access time exists. The solutions for both problems are even more efficient in the absence of contention, in which case their time complexity is a constant.

Original languageEnglish
Pages (from-to)539-556
Number of pages18
JournalSIAM Journal on Computing
Issue number2
StatePublished - Apr 1997


  • Consensus
  • Distributed computing
  • Mutual exclusion
  • Timing-based algorithms


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