Anna Pogosyants

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This paper presents a scalable approach to reasoning formally about distributed algorithms. It uses results about I/O 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 speci cation and deduction to discharge these obligations in a natural and(More)
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 termination within expected polynomial time. The Aspnes-Herlihy algorithm is a rather complex algorithm. Processes move through a succession of asynchronous(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)
The Probabilistic I/O 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)
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)
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)
The Probabilistic I/O Automaton model of 11] is used as the basis for a formal presentation and proof of the randomized consensus algorithm of Aspnes and Herlihy. The algorithm is highly nontrivial and guarantees termination within expected polynomial time. The task of carrying out this proof has led us to develop several general proof techniques for(More)
This thesis focuses on automatic theorem proving. In this area there is usually a tradeoff between the "generality" of a prover and the amount of user-guidance it requires to find a proof. This thesis demonstrates that the amount of guidance needed can be reduced by employing reasoning procedures for specialized theories. It presents an enhancement to the(More)
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 sacri cing the extensibility that makes subclassing useful to begin with. We argue that a class should have two interfaces, an instance interface used by programmers manipulating instances(More)
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