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Full-Text Articles in Physical Sciences and Mathematics
Equation-Based Congestion Control For Unicast Applications, Jitendra Padhye
Equation-Based Congestion Control For Unicast Applications, Jitendra Padhye
Computer Science Department Faculty Publication Series
This paper proposes a mechanismfor equation-based congestion control for unicast traffic. Most best-effort traffic in the current Internet is well-served by the dominant transport protocol TCP. However, traffic such as best-effort unicast streaming multimedia could find use for a TCP-friendly congestion control mechanism that refrains from reducing the sending rate in half in response to a single packet drop. With our mechanism, the sender explicitly adjusts its sending rate as a function of the measured rate of loss events, where a loss event consists of one or more packets dropped within a single round-trip time. We use both simulations and …
Combining Reinforcement Learning With A Local Control Algorithm, Jette Randløv
Combining Reinforcement Learning With A Local Control Algorithm, Jette Randløv
Computer Science Department Faculty Publication Series
We explore combining reinforcement learning with a hand-crafted local controller in a manner suggested by the chaotic control algorithm of Vincent, Schmitt and Vincent (1994). A closedloop controller is designed using conventional means that creates a domain of attraction about a target state. Chaotic behavior is used or induced to bring the system into this region, at which time the local controller is turned on to bring the system to the target state and stabilize it there. We describe experiments in which we use reinforcement learning instead of, and in addition to, chaotic behavior to learn an efficient policy for …
A Model For Compound Type Changes Encountered In Schema Evolution, Barbara Staudt Lerner
A Model For Compound Type Changes Encountered In Schema Evolution, Barbara Staudt Lerner
Computer Science Department Faculty Publication Series
Schema evolution is a problem that is faced by long-lived data. When a schema changes, existing persistent data can become inaccessible unless the database system provides mechanisms to access data created with previous versions of the schema. Most existing systems that support schema evolution focus on changes local to individual types within the schema, thereby limiting the changes that the database maintainer can perform. We have developed a model of type changes incorporating changes local to individual types as well as compound changes involving multiple types. The model describes both type changes and their impact on data by defining derivation …
Surplus Fair Scheduling: A Proportional-Share Cpu Scheduling Algorithm For Symmetric Multiprocessors, Abhishek Chandra, Micah Adler, Pawan Goyal, Prashant Shenoy
Surplus Fair Scheduling: A Proportional-Share Cpu Scheduling Algorithm For Symmetric Multiprocessors, Abhishek Chandra, Micah Adler, Pawan Goyal, Prashant Shenoy
Computer Science Department Faculty Publication Series
In this paper, we present surplus fair scheduling (SFS), a proportional-share CPU scheduler designed for symmetric multiprocessors. We first show that the infeasibility of certain weight assignments in multiprocessor environments results in unfairness or starvation in many existing proportional-share schedulers. We present a novel weight readjustment algorithm to translate infeasible weight assignments to a set of feasible weights. We show that weight readjustment enables existing proportional-share schedulers to significantly reduce, but not eliminate, the unfairness in their allocations. We then present surplus fair scheduling, a proportional-share scheduler that is designed explicitly for multiprocessor environments. We implement our scheduler in the …
Software Mode Changes For Continuous Motion Tracking, E. G. Araujo
Software Mode Changes For Continuous Motion Tracking, E. G. Araujo
Computer Science Department Faculty Publication Series
Robot control in nonlinear and nonstationary run-time environments presents challenges to traditional software methodologies. In particular, robot systems in “open” domains can only be modeled probabilistically and must rely on run-time feedback to detect whether hardware/software configurations are adequate. Modifications must be effected while guaranteeing critical performance properties. Moreover, in multi-robot systems, there are typically many ways in which to compensate for inadequate performance. The computational complexity of high dimensional sensorimotor systems prohibits the use of many traditional centralized methodologies. We present an application in which a redundant sensor array, distributed spatially over an office-like environment can be used to …
Constructive Feature Learning And The Development Of Visual Expertise, Justus H. Piater
Constructive Feature Learning And The Development Of Visual Expertise, Justus H. Piater
Computer Science Department Faculty Publication Series
We present a framework for learning features for visual discrimination. The learning system is exposed to a sequence of training images. Whenever it fails to recognize a visual context adequately, new features are sought that discriminate further between the true and false classes. Features consist of hierarchical combinations of primitive features (local edge and texture characteristics) that are sampled from example images. The system continues to learn better features even after all recognition errors have been eliminated, similarly to mechanisms underlying human visual expertise. Whenever the probabilistic recognition algorithm returns any posterior class probabilities greater than zero and less than …
Verifying Properties Of Process Definitions, Jamieson M. Cobleigh
Verifying Properties Of Process Definitions, Jamieson M. Cobleigh
Computer Science Department Faculty Publication Series
It seems important that the complex processes that synergize humans and computers to solve widening classes of societal problems be subjected to rigorous analysis. One approach is to use a process definition language to specify these processes and to then use analysis techniques to evaluate these definitions for important correctness properties. Because humans demand flexibility in their participation in complex processes, process definition languages must incorporate complicated control structures, such as various concurrency, choice, reactive control, and exception mechanisms. The underlying complexity of these control abstractions, however, often confounds the users’ intuitions as well as complicates any analysis. Thus, the …
Eligibility Traces For Off-Policy Policy Evaluation, Doina Precup, Richard S. Sutton, Satinder Singh
Eligibility Traces For Off-Policy Policy Evaluation, Doina Precup, Richard S. Sutton, Satinder Singh
Computer Science Department Faculty Publication Series
Eligibility traces have been shown to speed reinforcement learning, to make it more robust to hidden states, and to provide a link between Monte Carlo and temporal-difference methods. Here we generalize eligibility traces to off-policy learning, in which one learns about a policy different from the policy that generates the data. Off-policy methods can greatly multiply learning, as many policies can be learned about from the same data stream, and have been identified as particularly useful for learning about subgoals and temporally extended macro-actions. In this paper we consider the off-policy version of the policy evaluation problem, for which only …