ppxscal/embedding_network huggingface dataset:
RANDOMNESS AS A COMPUTATIONAL RESOURCE: ISSUES IN EFFICIENT COMPUTATION
Authors: Suresh Chari
Venue:  (1994)

Probabilistic methods have become an integral part of theoretical computer science. Typically, the use of randomization leads to solutions which are simple, elegant and more efficient than deterministic algorithms. A new research paradigm in randomized computation is to treat random bits as a resource and design algorithms which use random bits efficiently. The motivations for this approach are that algorithms which use fewer random bits are easier to implement. Also, algorithms using very few random bits can be made deterministic. For several problems all known efficient deterministic algorithms are obtained by this process of derandomization. We design new probabilistic techniques that are used to develop randomness--efficient algorithms for combinatorial optimization problems. The first problem we consider is the abstract problem of isolating one of a possibly exponentially sized set of feasible solutions to the input instance. This tool has been used previously to design algorithms for problems such as perfect matching in graphs, basic problems on matroids and designing random reductions. We design a new technique to solve this problem that is more efficient in the usage of random bits. Using this we derive randomness efficient solutions for the various applications. The randomness complexity of our method is parametrized in terms of the number of feasible solutions. As corollaries we obtain deterministic solutions for special cases of these problems. This new randomness--efficient technique unifies all previously known results for these applications and in many cases gives more efficient algorithms. We prove a strong lower bound which proves that our technique is optimal in the usage of random bits. Another important tool is the concept of random sources whose distribution approximates that of a truly random source. We present a new construction of such sources that is specifically tailored to be easily combined with the algorithmic design method of conditional probabilities. Using this we derive improved deterministic parallel algorithms for several combinatorial optimization problems. We investigate the problem of constructing small sample spaces which satisfy given constraints. For several sets of constraints we present improved constructions of such sample spaces. These have obvious applications to randomness--efficient computation and obtaining deterministic algorithms.
Superstabilizing Protocols for Dynamic Distributed Systems
Authors: Shlomi Dolev, Ted Herman
Venue:  (1997)

Two aspects of distributed-protocol reliability are the ability to recover from transient faults and the ability to function in a dynamic environment. Approaches for both of these aspects have been separately developed, but have revealed drawbacks when applied to environments with both transient faults and dynamic changes. This paper introduces definitions and methods for addressing both concerns in system design. A protocol is superstabilizing if it is (1) self-stabilizing, meaning that it is guaranteed to respond to an arbitrary transient fault by eventually satisfying and maintaining a legitimacy predicate, and it is (2) guaranteed to satisfy a passage predicate at all times when the system undergoes topology changes starting from a legitimate state. The passage predicate is typically a safety property that should hold while the protocol makes progress toward reestablishing legitimacy following a topology change. Specific contributions of the paper include: the definition of the class of superstabilizing protocols; metrics for evaluating superstabilizing protocols; superstabilizing protocols for coloring and spanning tree construction; a general method for converting self-stabilizing protocols into superstabilizing ones; and a generalized form of a self-stabilizing topology update protocol which may have useful applications for other research.
Virtual Audio - Three-Dimensional Audio in Virtual Environments
Authors: Daniel Adler
Venue:  (1996)

Three-dimensional interactive audio has a variety of potential uses in human-machine interfaces. After lagging seriously behind the visual components, the importance of sound is now becoming increas-ingly accepted. This paper mainly discusses background and techniques to implement three-dimensional audio in computer interfaces. A case study of a system for three-dimensional audio, implemented by the author, is described in great detail. The audio system was moreover integrated with a virtual reality system and conclusions on user tests and use of the audio system is presented along with proposals for future work at the end of the paper. The thesis begins with a definition of three-dimensional audio and a survey on the human auditory system to give the reader the needed knowledge of what three-dimensional audio is and how human auditory perception works. ---------------
An empirical evaluation of maximum likelihood voting in failure correlation conditions
Authors: K. Kim, M. A. Vouk, D. F. McAllister
Venue: Proceedings of the The Seventh International Symposium on Software Reliability Engineering (1996)

The maximum likelihood voting (MLV) strategy was recently proposed as one of the most reliable voting methods. The strategy determines the most likely correct result based on the reliability history of each software version. However, the theoretical results were obtained under the assumption that inter-version failures are not correlated by common cause faults. We first discuss the issues that arise in practical implementation of MLV, and present an extended version of the MLV algorithm that uses component reliability estimates to break voting ties. We then empirically evaluate the implemented MLV strategy in a situation where the inter-version failures are highly correlated. Our results show that, although in real situations MLV carries no reliability guarantees, it tends to be statistically more reliable, even under high inter-version correlation conditions, than other voting strategies that we have examined. We also compare implemented MLV performance with that of Recovery Block and hybrid Consensus Recovery Block approaches. Our results show that MLV often outperforms Recovery Block and that it can successfully compete with more elaborate Consensus Recovery Block. To the best of our knowledge, this is the first empirical evaluation of the MLV strategy.
Object-Based Ordered Delivery of Messages in Object-Based Systems
Authors: Tomoya Enokido, Hiroaki Higaki, Makoto Takizawa
Venue: Proceedings of the 1999 International Conference on Parallel Processing (1999)

Distributed applications are realized by cooperation of multiple objects. A state of an object depends on in what order the objects exchange request and response messages. In this paper, we newly define an object-based precedent relation of messages based on a conflicting relation among requests. Here, only the messages to be ordered in the object-based system are ordered and the others are not ordered. We discuss a protocol which supports the object-based ordered delivery of request and response messages. Here, an object vector is newly proposed to order messages.
An Architecture for Query Processing in Persistent Object Stores
Authors: Gail Mitchell, Stanley B. Zdonik, Umeshwar Dayal
Venue:  (1991)

Query optimizers for persistent object systems should be extensible to react to user-supplied abstract types. Although extensible optimizers exist, current architectures support only a single, non-extensible technique for controlling the optimization process. That is, the search strategy used by the optimizer is fixed when the optimizer is built. We propose an alternative to the current extensible architectures that will support multiple optimizer control strategies and the addition of new control strategies. The optimizer consists of a collection of optimization regions, each of which can transform queries according to a particular control strategy, set of transformations and cost model. A global optimizer control coordinates the movement of a query between these regions. This architecture provides extensibility in the optimizer''s repertoire of control strategies through the addition of new regions. In this paper we describe our approach and demonstrate its utility by following the optimizer as it works on an example query. The optimizer will move the query between three distinct regions, one that works with standard rule-based transformations, one that discovers join relationships in a query, and a third that manipulates a canonical join form. The first region acts similarly to existing rule-based optimizers, by applying algebraic rules to a query expression. The second region extends the optimizer to manipulate nested algebraic query expressions. The third manipulates join orderings in a query expression. The different regions illustrate different kinds of transformations and different strategies for application of those transformations. The optimizer can be extended with additional regions to provide more transformation types and control strategies, a result that cannot be achieved by existing relational or extensible optimizers.
On the complexity of intersecting finite state automata and NL versus NP
Authors: George Karakostas, Richard J. Lipton, Anastasios Viglas
Venue: Theoretical Computer Science (2003)

We consider uniform and non-uniform assumptions for the hardness of an explicit problem from finite state automata theory. First we show that a small improvement in the known straightforward algorithm for this problem can be used to design faster algorithms for subset sum and factoring, and improved deterministic simulations for non-deterministic time.On the other hand, we can use the same improved algorithm for our FSA problem to prove complexity class separation results (NL is not equal to P, or NP for the non-uniform case). This result can be viewed either as a hardness result for the FSA intersection problem, or as a method for separating NL from P or NP. It is interesting to note that this approach is based on a more general method for separating two complexity classes, using algorithms rather than lower bounds.
On Limited versus Polynomial Nondeterminism
Authors: Uriel Feige, Joe Kilian
Venue:  (1997)

In this paper, we show that efficient algorithms for some problems that require limited nondeterminism imply the subexponential simulation of nondeterministic computation by deterministic computation. In particular, if cliques of size O(log n) can be found in polynomial time, then nondeterministic time f(n) is contained in deterministic time 2^{O(\sqrt{f(n)polylog f(n)})}.
Spatial Structure in Low Dimensions for
Authors: Bramson M., Lebowitz J. L.
Venue:  (2000)

Consider the system of particles on ${\Bbb Z}^d$ where particles are of two types, $A$ and $B$, and execute simple random walks in continuous time. Particles do not interact with their own type, but when a type $A$ particle meets a type $B$ particle, both disappear. Initially, particles are assumed to be distributed according to homogeneous Poisson random fields, with equal intensities for the two types. This system serves as a model for the chemical reaction $A+B\to inert$. In [BrLe91a], the densities of the two types of particles were shown to decay asymptotically like $1/t^{d/4}$ for $d>4$ and $1/t$ for $d\geq 4$, as $t\to\infty$. This change in behavior from low to high dimensions corresponds to a change in spatial structure. In $d4$, both particle types are, at large times, present locally in concentrations not depending on the type, location or realization. In $d=4$, both particle types are present locally, but with varying concentrations. Here, we analyze this behavior in $d>4$; the behavior for $d\geq 4$ will be handled in a future work [BrLe99].
Admission Control and Loss Management for an Application-Level Statistical Service
Authors: Geoffrey G. Xie, Simon S. Lam
Venue: Proceedings of the 1997 International Conference on Network Protocols (ICNP '97) (1997)

We present an admission control framework and loss management techniques in support of a guaranteed statistical service. The service is characterized by (i) the loss rate of application data units (ADUs) bounded below a specified value, and (ii) ADU losses distributed evenly among flows subscribing to the service and uniformly over the duration of each how. Specifically, a flow is modeled as a sequence of bursts, each of which is a sequence of packets that carry the bits of an ADU. The first packet of each burst carries information on the ADlJ (e.g., its bandwidth requirement). This traffic model enables admission control at the burst level as well as at the flow level. Such a two level admission control approach is very effective in bounding end-to-end ADU loss rates of flows while maintaining high channel utilization in the network. The traffic model also enables simple techniques that can be used at a network channel to distribute ADU losses evenly among flows subscribing to the same statistical service, and to protect high priority ADUs (e.g., I frames of MPEG applications).
What causes a Neuron to spike?
Authors: Blaise Agüera y Arcas, Adrienne L. Fairhall
Venue: Neural Computation (2003)

The computation performed by a neuron can be formulated as a combination of dimensional reduction in stimulus space and the nonlinearity inherent in a spiking output. White noise stimulus and reverse correlation (the spike-triggered average and spike-triggered covariance) are often used in experimental neuroscience to "ask" neurons which dimensions in stimulus space they are sensitive to and to characterize the nonlinearity of the response. In this article, we apply reverse correlation to the simplest model neuron with temporal dynamics--the leaky integrate-and-fire model--and find that for even this simple case, standard techniques do not recover the known neural computation. To overcome this, we develop novel reverse-correlation techniques by selectively analyzing only "isolated" spikes and taking explicit account of the extended silences that precede these isolated spikes. We discuss the implications of our methods to the characterization of neural adaptation. Although these methods are developed in the context of the leaky integrate-and-fire model, our findings are relevant for the analysis of spike trains from real neurons.
Some Mechanisms to Improve TCP/IP Performance over wireless and Mobile Computing Environment
Authors: Wen-Tsuen Chen, Jyh-Shin Lee
Venue: Proceedings of the Seventh International Conference on Parallel and Distributed Systems (2000)

The Internet and wireless networks are two of the most important technical developments that have had a direct effect on the lives of people over the past few years. The next step is to combine these two technologies to provide wide-area wireless Internet access. Currently Transport Control Protocol/Internet Protocol (TCP/IP) is the most important protocol integrates a wide range of different physical networks into a global Internet. The environment of wireless networks violates many assumptions made by traditional TCP/IP. Compared with fixed and wired networks, the wireless networks have high bit-error rate (BER) and offer less available bandwidth. Furthermore, the host mobility also results in packet loss or delay during handoff procedures. Hence, the performance of TCP/IP over such wireless networks without any modification would suffer significant degradation of throughput and high interactive delay. In this paper, we propose some schemes to improve the performance of TCP/IP over wireless networks according to their characteristics. In this paper, we analyze the performance of TCP/IP under different network conditions by using ns-2 simulator to facilitate comparisons with previous studies. The simulation results show that our proposed mechanisms achieve better performance than other protocols.
ZYGLOTRON User''s Manual
Authors: D J Becher, B J Rosenberg
Venue:  (1988)

As the name implies, this document is intended for those people interested in using the Zyglotron simulator. Zyglotron is a multi-process, vectorized behavioral simulator for {\em BLITZEN}, a massively-parallel SIMD architecture based on the Massively Parallel Processor (MPP). For efficient use of the simulator, users should have an intimate knowledge of the {\em BLITZEN} architecture, as well as a basic familiarity with the Zyglotron design. Readers are directed to several documents for this information.
A Tight Upper Bound on the Benefits of Replication and Consistency Control Protocols
Authors: Donald B. Johnson, Larry Raab
Venue:  (1990)

We present an upper bound on the performance provided by a protocol guaranteeing mutually exclusive access to a replicated resource in a network subject to component failure and subsequent partitioning. The bound is presented in terms of the performance of a single resource in the same network. The bound is tight and is the first such bound known to us. Since mutual exclusion is one of the requirements for maintaining the consistency of a database object, this bound provides an upper limit on the availability provided by any database consistency control protocol, including those employing dynamic data relocation and replication. We show that if a single copy provides availability A for 0 ? A ? 1, then no scheme can achieve availability greater than ?A in the same network. We show this bound to be the best possible for any network with availability greater than .25. Although, as we proved, the problem of calculating A is #P-complete, we describe a method for approximating the optimal location for a single copy which adjusts dynamically to current network characteristcs. This bound is most useful for high availabilities, which tend to be obtainable with modern networks and their constituent components.
Load profiling: a methodology for scheduling real-time tasks in a distributed system
Authors: A. Bestavros
Venue: Proceedings of the 17th International Conference on Distributed Computing Systems (ICDCS '97) (1997)

Traditionally, the goal of load management protocols for distributed systems has been to ensure that nodes are equally loaded. We show that for real time systems, load balancing is not desirable since it results in the available bandwidth being distributed equally amongst all nodes-in effect making all nodes in the system capable of offering almost the same bandwidth (e.g., in cycles per second) to incoming tasks. We show that this "one size fits all" practice leads to a higher rate of missed deadlines as incoming tasks may be denied service because they require bandwidth that cannot be granted at any single node-while plenty of fragmented bandwidth is collectively available in the system. We propose a new load profiling strategy that allows the nodes of a distributed system to be unequally loaded so as to maximize the chances of finding a node that would satisfy the computational needs of incoming real time tasks. The performance of the proposed protocol is evaluated via simulation, and is contrasted to other dynamic scheduling protocols for real time distributed systems.
Representation Inheritance: A Safe Form of "White Box'' Code Inheritance
Authors: Stephen H. Edwards
Venue: Proceedings of the 4th International Conference on Software Reuse (1996)

There are two approaches to using code inheritance for defining new component implementations in terms of existing implementations. Black box code inheritance allows subclasses to reuse superclass implementations as-is, without direct access to their internals. Alternatively, white box code inheritance allows subclasses to have direct access to superclass implementation details, which may be necessary for the efficiency of some subclass operations. Unfortunately, white box code inheritance violates the protection that encapsulation affords superclasses, opening up the possibility of a subclass interfering with the correct operation of its superclass' methods. Representation inheritance is proposed as a restricted form of white box code inheritance where subclasses have direct access to superclass implementation details, but are required to respect the representation invariant(s) and abstraction relation(s) of their ancestor(s). This preserves the protection that encapsulation provides, while allowing the freedom of access that component implementers sometimes desire.
Exploiting cost distributions for query optimization
Authors: Florian Waas, J. Pellenkoft
Venue:  (1998)

Large-scale query optimization is, besides its practical relevance, a hard test case for optimization techniques. Since exact methods cannot be applied due to the combinatorial explosion of the search space, heuristics and probabilistic strategies have been deployed for more than a decade. However, the results achieved are subject to discussion as several performance-critical effects still lack a sound explanation. In this paper we show how the cost distribution within these search spaces can be exploited. We analyze costing techniques and their principles to assess the difficulty of optimizing queries. Our investigation points out distinct characteristics of the cost distribution caused by the tree structure of the query plans. Applying basic stochastics to those distributions shows that random plan generation qualifies as a highly effective optimization technique under the precondition that every possible query plan may be generated with a positive probability. We present a run-time optimized algorithm meeting this requirement. Our experiments confirm the analytical results and demonstrate the algorithm''s efficiency.
A distributed global queue transmission strategy for a WDM optical fiber network
Authors: E. M. Foo, T. G. Robertazzi
Venue: Proceedings of the Fourteenth Annual Joint Conference of the IEEE Computer and Communication Societies (Vol. 1)-Volume - Volume 1 (1995)

A new distributed global queueing strategy and medium access protocol that users employ to schedule their transmissions to avoid receiver collisions is introduced for an optical fiber network. The network uses wavelength division multiplexing (WDM) for the data channels. The medium access control utilizes TDMA on the control channel to allow users to implement a global reservation scheme to send data packets. The data channels operate under a distributed demand assignment scheme that allows receiver collision-free operation and efficient scheduling. An analytical solution is obtained via equilibrium point analysis (EPA). It was shown that the maximum throughput obtained is approximately 42% which exceeds the maximum throughput of ALOHA based medium access protocols. The delay is shown to be relatively constant for a wide range of operation.
An Adaptive Object Storage System for Mobile Computers
Authors: Tatsuo Nakajima
Venue: Proceedings of the Seventh International Conference on Parallel and Distributed Systems: Workshops (2000)

This paper describes an adaptive object storage system for mobile computing environments. The object storage system adopts the object graph framework, and changes the configuration of its stricture according to computing environments. The object graph framework that is proposed in the paper is useful techniques for building adaptive software.
A Proof System for the pi-calculus
Authors: Roberto Amadio, Mads Dam
Venue:  (1996)

We study the problem of specifying and verifying properties of pi-calculus processes while relying on a bisimulation semantics. As our property specification language we use a version of the modal mu-calculus adapted to the pi-calculus. We show that the logical language is sufficiently expressive to characterize by means of a finite formula a process up to any approximation of the bisimulation relation. We consider the problem of checking that a process of the pi-calculus satisfies a specification expressed in this modal mu-calculus. We develop an algorithm which is sound in general, and complete for processes having a finite reachability property. Finally, we present a proof system which can be applied to prove non-recursive properties of arbitrary processes. We show that the system is complete on the non-recursive fragment of the logical language.