A Faster Counting Protocol for Anonymous Dynamic Networks

We study the problem of counting the number of nodes in a slotted-time communication network, under the challenging assumption that nodes do not have identifiers and the network topology changes frequently. That is, for each time slot links among nodes can change arbitrarily provided that the network is always connected. Tolerating dynamic topologies is crucial in face of mobility and unreliable communication whereas, even if identifiers are available, it might be convenient to ignore them in massive networks with changing topology. Counting is a fundamental task in distributed computing since knowing the size of the system often facilitates the design of solutions for more complex problems. Currently, the best upper bound proved on the running time to compute the exact network size is double-exponential. However, only linear complexity lower bounds are known, leaving open the question of whether efficient Counting protocols for Anonymous Dynamic Networks exist or not. In this paper we make a significant step towards answering this question by presenting a distributed Counting protocol for Anonymous Dynamic Networks which has exponential time complexity. Our algorithm ensures that eventually every node knows the exact size of the system and stops executing the algorithm. Previous Counting protocols have either double-exponential time complexity, or they are exponential but do not terminate, or terminate but do not provide running-time guarantees, or guarantee only an exponential upper bound on the network size. Other protocols are heuristic and do not guarantee the correct count

Insertion Sort is O(n log n)

Traditional Insertion Sort runs in O(n^2) time because each insertion takes O(n) time. When people run Insertion Sort in the physical world, they leave gaps between items to accelerate insertions. Gaps help in computers as well. This paper shows that Gapped Insertion Sort has insertion times of O(log n) with high probability, yielding a total running time of O(n log n) with high probability.Comment: 6 pages, Latex. In Proceedings of the Third International Conference on Fun With Algorithms, FUN 200

Multi-round Master-Worker Computing: a Repeated Game Approach

We consider a computing system where a master processor assigns tasks for execution to worker processors through the Internet. We model the workers decision of whether to comply (compute the task) or not (return a bogus result to save the computation cost) as a mixed extension of a strategic game among workers. That is, we assume that workers are rational in a game-theoretic sense, and that they randomize their strategic choice. Workers are assigned multiple tasks in subsequent rounds. We model the system as an infinitely repeated game of the mixed extension of the strategic game. In each round, the master decides stochastically whether to accept the answer of the majority or verify the answers received, at some cost. Incentives and/or penalties are applied to workers accordingly. Under the above framework, we study the conditions in which the master can reliably obtain tasks results, exploiting that the repeated games model captures the effect of long-term interaction. That is, workers take into account that their behavior in one computation will have an effect on the behavior of other workers in the future. Indeed, should a worker be found to deviate from some agreed strategic choice, the remaining workers would change their own strategy to penalize the deviator. Hence, being rational, workers do not deviate. We identify analytically the parameter conditions to induce a desired worker behavior, and we evaluate experi- mentally the mechanisms derived from such conditions. We also compare the performance of our mechanisms with a previously known multi-round mechanism based on reinforcement learning.Comment: 21 pages, 3 figure

¿Están protocolizadas las actividades de enfermería para un paciente diabético en una unidad de hemodiálisis?

[Resumen] INTRODUCCIÓN: La enfermedad renal crónica es un síndrome clínico causado por una insuficiencia renal progresiva e irreversible. Los pacientes que padecen ERC que se encuentran en tratamiento sustitutivo renal, tienen unas necesidades muyconcretas y específicas y un riesgo muy elevado de sufrir complicaciones durante la hemodiálisis, siendo mayor en pacientes con diabetes mellitus como enfermedad asociada. Es en este contexto donde guías y protocolos juegan un papel fundamental, en la medida en que permiten la estandarización de la práctica clínica (22), por parte de los profesionales sanitarios que intervienen en el cuidado de estos pacientes.[Resumo] A enfermidade renal crónica é unha síndrome clínica causada por un fallo renal progresivae irreversible. Os pacientes con ERC que están en terapia de substitución renal, teñen necesidades moi especí-ficas e únicas e un risco moi elevado de complicacións durante a hemodiá-lise moito maior en pacientes con diabetes mellitus e enfermidades asocia-das. É neste contexto que as directrices e protocolos desempeñan un papel fundamental, na medida en que permiten a estandarización da práctica clí-nica (22), por profesionais sanitarios implicados no tratamento destes pa-cientes.[Abstract] Chronic kidney disease is a clinical syndrome caused by a progressive and irreversible renal failure. Patients with CKD who are on renalreplacement therapy, have very specific and unique needs and a very high risk of complications during hemodialysis was higher in patients with diabetes mellitus and associated disease. It is in this context that gui-delines and protocols play a key role, to the extent that allow standardiza-tion of clinical practice (22), by health professionals involved in the care of these patients.Traballo fin de grao (UDC.FEP). Enfermaría. Curso 2015/101