9952136
Using a distributed single address space operating system to support modern cluster computing
Recent 64-bit microprocessors have made a huge 18.4 quintillion byte address space potentially available to programs. This has led to the design of operating systems that provide a single virtual address space in which all code and data reside in and across all levels of storage and all nodes of a distributed system. These operating systems, called single address space operating systems (SASOSs), have characteristics that can be used to support modern cluster computing in a distributed system in ways that provide an improved program development environment and higher performance than is available from conventional operating systems. Sombrero, our SASOS design, makes use of its hardware support for object-grained protection, separate thread-related protection domains and implicit protection domain crossing to provide support for modern cluster computing which is not available in SASOSs built on stock processors. Its design, which provides direct system-level support for object-oriented programming, includes a number of features targeted specifically at modern cluster computing.
35435747
The Sombrero Single Address Space Operating System Prototype A Testbed for Evaluating Distributed Persistent System Concepts and Implementation
The Sombrero distributed single address space operating system prototype is currently being implemented. The prototype includes an emulation of CPU-resident protection hardware necessary to fully utilize the properties of a single address space. The primary objective of the Sombrero project is to demonstrate that software development costs are sharply reduced in a single address space environment with no reduction in performance. This paper presents Sombrero design decisions and implementation mechanisms developed in order to support protection, communication, resource access and control transfer across a very large persistent distributed address space. Included are changes to operating system architecture, evolution of programming types and a new approach to distributed consistency management in a single address space based-DSM system that is being integrated into the prototype.
17886110
Using a single address space operating system for distributed computing and high performance
Recent 64-bit microprocessors have made a huge 18.4 quintillion byte address space potentially available to programs. This has led to the design of Operating Systems that provide a single virtual address space in which all code and data reside in and that spans all levels of storage and all nodes of a distributed system. These operating systems called SASOSs, have characteristics that can be used to support synchronization and coherency in a distributed system in ways that provide an improved program development environment and higher performance than that available from conventional operating systems. Sombrero, our SASOS design, makes use of its hardware support for object-grained protection, separate thread related protection domains and implicit protection domain crossing to provide synchronization and coherency support for distributed object copy set management not available in SASOSs built on stock processors. Its design, which provides direct system level support for object oriented programming includes a number of system architectural features targeted at modern distributed computing.
3255666
Logic Programming in a Fragment of Intuitionistic Linear Logic
The intuitionistic notion of context is refined by using a fragment of J.-Y. Girard's (Theor. Comput. Sci., vol.50, p.1-102, 1987) linear logic that includes additive and multiplicative conjunction, linear implication, universal quantification, the of course exponential, and the constants for the empty context and for the erasing contexts. It is shown that the logic has a goal-directed interpretation. It is also shown that the nondeterminism that results from the need to split contexts in order to prove a multiplicative conjunction can be handled by viewing proof search as a process that takes a context, consumes part of it, and returns the rest (to be consumed elsewhere). Examples taken from theorem proving, natural language parsing, and database programming are presented: each example requires a linear, rather than intuitionistic, notion of context to be modeled adequately. >
16135339
A multiple-conclusion meta-logic
The theory of cut-free sequent proofs has been used to motivate and justify the design of a number of logic programming languages. Two such languages, /spl lambda/Prolog and its linear logic refinement, Lolli (J. Hodas and D. Miller, 1994), provide for various forms of abstraction (modules, abstract data types, higher-order programming) but lack primitives for concurrency. The logic programming language, LO (Linear Objects) (J. Andreoli and R. Pareschi, 1991) provides for concurrency but lacks abstraction mechanisms. We present Forum, a logic programming presentation of all of linear logic that modularly extends the languages /spl lambda/Prolog, Lolli, and LO. Forum, therefore, allows specifications to incorporate both abstractions and concurrency. As a meta-language, Forum greatly extends the expressiveness of these other logic programming languages. To illustrate its expressive strength, we specify in Forum a sequent calculus proof system and the operational semantics of a functional programming language that incorporates such nonfunctional features as counters and references.<<ETX>>
17425751
A Mixture of Experts Classifier with Learning Based on Both Labelled and Unlabelled Data
We address statistical classifier design given a mixed training set consisting of a small labelled feature set and a (generally larger) set of unlabelled features. This situation arises, e.g., for medical images, where although training features may be plentiful, expensive expertise is required to extract their class labels. We propose a classifier structure and learning algorithm that make effective use of unlabelled data to improve performance. The learning is based on maximization of the total data likelihood, i.e. over both the labelled and unlabelled data subsets. Two distinct EM learning algorithms are proposed, differing in the EM formalism applied for unlabelled data. The classifier, based on a joint probability model for features and labels, is a "mixture of experts" structure that is equivalent to the radial basis function (RBF) classifier, but unlike RBFs, is amenable to likelihood-based training. The scope of application for the new method is greatly extended by the observation that test data, or any new data to classify, is in fact additional, unlabelled data - thus, a combined learning/classification operation - much akin to what is done in image segmentation - can be invoked whenever there is new data to classify. Experiments with data sets from the UC Irvine database demonstrate that the new learning algorithms and structure achieve substantial performance gains over alternative approaches.
42391520
Are You Being Served?
There has been a lot of talk about service robots over the past decade, and indeed some service robots are starting to make their way into the real world; delivering food in hospitals, turning book pages for people with physical diabilities, and the like. Unfortunately, while functional, these robots perform their jobs with all the panache of machines. When people want service robots they really want “servant robots” but without the social guilt that now often accompanies the hiring of actual human servants. To do servants correctly, it is necessary to have a hierarchy in the ‘help’. Only the Dark Knight has been able to maintain style and social standing with a single servant The AAAI-97 Conference Reception is the AI community’s social event of the season. Here, as with almost all AI activities, style and social standing are everything. AI researchers work hard, and when they party, they want to be pampered. Procuring one’s own food is gauche; the AI community wants to be served. Towards this end, KIPR is creating a pair of servant robots (Capt. Peacock and Mr. Humphries) to serve and cater to their charges every gastromical need, while maintaining that old-world flavor that lets you know that while your servants may be smarter, stronger and more expensive than you, they are definitely your social inferiors.
3091178
Using Linear Logic to Reason about Sequent Systems
Linear logic can be used as a meta-logic for the specification of some sequent calculus proof systems. We explore in this paper properties of such linear logic specifications. We show that derivability of one proof system from another has a simple decision procedure that is implemented simply via bounded logic programming search. We also provide conditions to ensure that an encoded proof system has the cut-elimination property and show that this can be decided again by simple, bounded proof search algorithms.