Tars: Timeliness-aware Adaptive Replica Selection for Key-Value Stores

In current large-scale distributed key-value stores, a single end-user request may lead to key-value access across tens or hundreds of servers. The tail latency of these key-value accesses is crucial to the user experience and greatly impacts the revenue. To cut the tail latency, it is crucial for clients to choose the fastest replica server as much as possible for the service of each key-value access. Aware of the challenges on the time varying performance across servers and the herd behaviors, an adaptive replica selection scheme C3 is proposed recently. In C3, feedback from individual servers is brought into replica ranking to reflect the time-varying performance of servers, and the distributed rate control and backpressure mechanism is invented. Despite of C3's good performance, we reveal the timeliness issue of C3, which has large impacts on both the replica ranking and the rate control, and propose the Tars (timeliness-aware adaptive replica selection) scheme. Following the same framework as C3, Tars improves the replica ranking by taking the timeliness of the feedback information into consideration, as well as revises the rate control of C3. Simulation results confirm that Tars outperforms C3.Comment: 10pages,submitted to ICDCS 201

Black Holes and Random Matrices

We argue that the late time behavior of horizon fluctuations in large anti-de Sitter (AdS) black holes is governed by the random matrix dynamics characteristic of quantum chaotic systems. Our main tool is the Sachdev-Ye-Kitaev (SYK) model, which we use as a simple model of a black hole. We use an analytically continued partition function $|Z(\beta +it)|^2$ as well as correlation functions as diagnostics. Using numerical techniques we establish random matrix behavior at late times. We determine the early time behavior exactly in a double scaling limit, giving us a plausible estimate for the crossover time to random matrix behavior. We use these ideas to formulate a conjecture about general large AdS black holes, like those dual to 4D super-Yang-Mills theory, giving a provisional estimate of the crossover time. We make some preliminary comments about challenges to understanding the late time dynamics from a bulk point of view.Comment: 73 pages, 15 figures, minor errors correcte

Spartan Daily, May 25, 1962

Volume 49, Issue 127https://scholarworks.sjsu.edu/spartandaily/4314/thumbnail.jp

Science materials for the gifted in grades two and three

Thesis (Ed.M.)--Boston Universit

Lost on Purpose

In nine linked nonfiction essays and eight codas, the author seeks to understand the meaning of being lost and the importance of not knowing in an era of instantaneous and ubiquitous information. Through extensive interviews, research, and memoir, the author seeks out those who choose to live lost in order to understand his own penchant for escape. Framed by the mystery of antique maps, these essays find the author in several different locations, from Tasmania to Siberia to Utah. In each, the author meets and spends time with an ambassador of each place before finally attempting to become lost himself

Born in an Infinite Universe: a Cosmological Interpretation of Quantum Mechanics

We study the quantum measurement problem in the context of an infinite, statistically uniform space, as could be generated by eternal inflation. It has recently been argued that when identical copies of a quantum measurement system exist, the standard projection operators and Born rule method for calculating probabilities must be supplemented by estimates of relative frequencies of observers. We argue that an infinite space actually renders the Born rule redundant, by physically realizing all outcomes of a quantum measurement in different regions, with relative frequencies given by the square of the wave function amplitudes. Our formal argument hinges on properties of what we term the quantum confusion operator, which projects onto the Hilbert subspace where the Born rule fails, and we comment on its relation to the oft-discussed quantum frequency operator. This analysis unifies the classical and quantum levels of parallel universes that have been discussed in the literature, and has implications for several issues in quantum measurement theory. It also shows how, even for a single measurement, probabilities may be interpreted as relative frequencies in unitary (Everettian) quantum mechanics. We also argue that after discarding a zero-norm part of the wavefunction, the remainder consists of a superposition of indistinguishable terms, so that arguably "collapse" of the wavefunction is irrelevant, and the "many worlds" of Everett's interpretation are unified into one. Finally, the analysis suggests a "cosmological interpretation" of quantum theory in which the wave function describes the actual spatial collection of identical quantum systems, and quantum uncertainty is attributable to the observer's inability to self-locate in this collection.Comment: 17 pages, 2 figures; revised version to match published version, including authorship change. Abstract is abridge

Restorative Rigging and the Safe Indication Account

Typical Gettieresque scenarios involve a subject, S, using a method, M, of believing something, p, where, normally, M is a reliable indicator of the truth of p, yet, in S’s circumstances, M is not reliable: M is deleteriously rigged. A different sort of scenario involves rigging that restores the reliability of a method M that is deleteriously rigged: M is restoratively rigged. Some theorists criticize (among others) the safe indication account of knowledge defended by Luper, Sosa, and Williamson on the grounds that it treats such cases as knowledge. But other theorists also criticize the safe indication account because it treats the cases as examples of ignorance when they are really examples of knowledge. I answer both groups of critics by arguing that (1) restorative rigging can enable us to know things, and (2) restoratively rigged cases can meet the relevant conditions of the safe indication account

Emergency Evacuation Software Model For Simulation Of Physical Changes

Public space such as schools, cinemas, shopping malls, etc. must have an emergency evacuation system in place. Such places are also required to follow certain regulations and protocols for emergency evacuation to assure the safety of their occupants inside from any unpredictable incident. For nearly two decades, companies/organizations are using simulation models/software for evacuation planning. Researchers are working on these software models to improve the efficiency using latest algorithms. This thesis focuses on creating a base software model of evacuation systems for 3D indoor environments to simulate physical changes such as retractable chairs, movable walls etc., to evaluate their effectiveness before committing to those changes. This research tries to address various flaws and shortcomings of previous software. We are using tools like Unity 3D and Autodesk Maya to simulate suggested changes. It provides planners as well as researchers a new perspective to work on new recommended physical changes to design public venues