Anna Pogosyants

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This paper is written in memory of Anna Pogosyants, who died in a car crash in December 1995 while working on this project for her Ph.D. dissertation. Summary. The Probabilistic I/O Automaton model of [31] is used as the basis for a formal presentation and proof of the randomized consensus algorithm of Aspnes and Herlihy. The algorithm guarantees(More)
This paper presents a scalable approach to reasoning formally about distributed algorithms. It uses results about IIO automata to extract a set of proof obligations for showing that the behaviors of one algorithm are among those of another, and it uses the Larch tools for speciication and deduction to discharge these obligations in a natural and(More)
In [11] a method for the analysis of the expected time complexity of a randomized distributed algorithm is presented. The method consists of proving auxiliary probabilistic time bound statements of the form U ~ U', which mean that whenever the algorithm begins in 'a state in set U, it will reach a state in set U' within time t with probability at least p.(More)
A formal representation and machine-checked proof are given for the Bounded Concurrent Timestamp (BCTS) algorithm of Dolev and Shavit. The proof uses invariant assertions and a forward simulation mapping to a corresponding Unbounded Concurrent Timestamp (UCTS) algorithm, following a strategy developed by Gawlick, Lynch, and Shavit. The proof was produced(More)
Randomization is an exceptional tool for the design of distributed algorithms, sometimes yielding eecient solutions to problems that are inherently complex, or even unsolvable, in the setting of deterministic algorithms. However, this tool has a price: even simple randomized algorithms can be extremely hard to verify and analyze. This thesis addresses the(More)
The Probabilistic IIO Automaton model of 20 is used as the basis for a formal presentation and proof of the randomized consensus algorithm of Aspnes and Herlihy. The algorithm guarantees termination within expected polynomial time. The Aspnes-Herlihy algorithm is a rather complex algorithm. Processes move through a succession of asynchronous rounds,(More)
  • Steve Garland, Alan Heydon, +16 authors Jeannette Wing David Evans
  • 1997
Classes are harder to subclass than they need be. This report addresses this problem, showing how to design classes that are more modular and easier to subclass without sacriicing the extensibility that makes subclassing useful to begin with. We argue that a class should have t w o i n terfaces, an instance interface used by programmers manipulating(More)
A formal representation and machine-checked proof are given for the Bounded Concurrent Timestamp BCTS algorithm of Dolev and Shavit. The proof uses invariant assertions and a forward simulation mapping to a corresponding Unbounded Concurrent Timestamp UCTS algorithm, following a strategy developed by G a wlick, Lynch, and Shavit. The proof was produced(More)
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