Hammurabi Mendes

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The problem of &#949;-approximate agreement in Byzantine asynchronous systems is well-understood when all values lie on the real line. In this paper, we generalize the problem to consider values that lie in R<sup>m</sup>, for m &#8805; 1, and present an optimal protocol in regard to fault tolerance. Our scenario is the following. Processes start with values(More)
Priority queues are fundamental abstract data structures, often used to manage limited resources in parallel programming. Several proposed parallel priority queue implementations are based on skiplists, harnessing the potential for parallelism of the add() operations. In addition, methods such as Flat Combining have been proposed to reduce contention by(More)
Consider a network of $$n$$ n processes, where each process inputs a $$d$$ d -dimensional vector of reals. All processes can communicate directly with others via reliable FIFO channels. We discuss two problems. The multidimensional Byzantine consensus problem, for synchronous systems, requires processes to decide on a single $$d$$ d -dimensional vector $$v(More)
In this work, we extend the topology-based approach for characterizing computability in asynchronous crash-failure distributed systems to asynchronous Byzantine systems. We give the first theorem with necessary and sufficient conditions to solve arbitrary tasks in asynchronous Byzantine systems where an adversary chooses faulty processes. For colorless(More)
In this paper, we extend the topological model that characterizes task solvability in crashfailure systems to colorless tasks in Byzantine asynchronous systems. We give the first theorem with necessary and sufficient conditions to solve arbitrary colorless tasks in such model, capturing the relation between the total number of processes, the number of(More)
This paper provides a theoretical and practical framework for crash-resilient data structures on a machine with persistent (nonvolatile) memory but transient registers and cache. In contrast to certain prior work, but in keeping with “real world” systems, we assume a full-system failure model, in which all transient state (of all processes) is lost on a(More)
Nonvolatile, byte-addressable memory (NVM) will soon be commercially available, but registers and caches are expected to remain transient on most machines. Without careful management, the data preserved in the wake of a crash are likely to be inconsistent and thus unusable. Previous work has explored the semantics of instructions used to push the contents(More)
Protein Folding is concerned with the reasons and mechanism behind a protein’s tertiary structure. The thermodynamic hypothesis of Anfinsen postulates an universal energy function (UEF) characterizing the tertiary structure, defined consistently across proteins, in terms of their aminoacid sequence. We consider the approach of examining multiple protein(More)
In this paper, we show that the protocol complex of a Byzantine synchronous system can remain (k− 1)-connected for up to ⌈t/k⌉ rounds, where t is the maximum number of Byzantine processes, and t ≥ k ≥ 1. Protocol complex connectivity is important since a (k − 1)-connected protocol complex does not admit solutions for the k-set agreement problem. In(More)