ppxscal/embedding_network huggingface dataset:
Learning to Take Actions
Authors: Roni Khardon
Venue: Machine Learning (1999)

We formalize a model for supervised learning of action strategies in dynamic stochastic domains and show that PAC-learning results on Occam algorithms hold in this model as well. We then identify a class of rule-based action strategies for which polynomial time learning is possible. The representation of strategies is a generalization of decision lists&semi; strategies include rules with existentially quantified conditions, simple recursive predicates, and small internal state, but are syntactically restricted. We also study the learnability of hierarchically composed strategies where a subroutine already acquired can be used as a basic action in a higher level strategy. We prove some positive results in this setting, but also show that in some cases the hierarchical learning problem is computationally hard.
Multiple Multicast with Minimized Node Contention on Wormhole k-ary n-cube Networks
Authors: Ram Kesavan, Dhabaleswar K. Panda
Venue: IEEE Transactions on Parallel and Distributed Systems (1999)

This paper presents a new approach to minimize node contention while performing multiple multicast/broadcast on wormhole $k$-ary $n$-cube networks with overlapped destination sets. The existing multicast algorithms in the literature deliver poor performance under multiple multicast because these algorithms have been designed with only single multicast in mind. The new algorithms introduced in this paper do not use any global knowledge about the respective destination sets of the concurrent multicasts. Instead, only local information and a source-specific partitioning approach are used. For systems supporting unicast message-passing, a new SPUmesh (Source-Partitioned Umesh) algorithm is proposed and is shown to be superior than the conventional Umesh algorithm [2] for multiple multicast. Two different algorithms, SQHL (Source-Quadrant Hierarchical Leader) and SCHL (Source-Centered Hierarchical Leader), are proposed for systems with multidestination message-passing and shown to be superior than the HL scheme [3]. All of these algorithms perform 1) 5-10 times faster than the existing algorithms under multiple multicast and 2) as fast as existing algorithms under single multicast. Furthermore, the SCHL scheme demonstrates that the latency of multiple multicast can, in fact, be reduced as the degree of multicast increases beyond a certain number. Thus, these algorithms demonstrate significant potential to be used for designing fast and scalable collective communication libraries on current and future generation wormhole systems.
Mean Cost Cyclical Game
Authors: Rick L. Andrews, Ajay K. Manrai, Nikolai Pisaruk
Venue: Mathematics of Operations Research (1999)

We study the mean cost cyclical game in a more general setting than that in Gurvitch et al. (1988) and Karzanow and Lebedev (1993). The game is played on a directed graph and generalizes the single source shortest path problem, the minimum mean cycle problem (see Karp 1978), and the ergodic extension of matrix games (Moulin 1976). We prove the existence of a solution in uniform stationary strategies and present an algorithm for finding such optimal strategies. In fact, our algorithm is an extension of the algorithms due to Gurvitch et al. (1988) and Karzanow and Lebedev (1993), which were proved to be finite, but exponential in the worst case. We prove that all these algorithms are pseudopolynomial.
Stochastic Spatial Models
Authors: Rick Durrett
Venue: SIAM Review (1999)

In the models we will consider, space is represented by a grid of sites that can be in one of a finite number of states and that change at rates that depend on the states of a finite number of sites. Our main aim here is to explain an idea of Durrett and Levin (1994): the behavior of these models can be predicted from the properties of the mean field ODE, i.e., the equations for the densities of the various types that result from pretending that all sites are always independent. We will illustrate this picture through a discussion of eight families of examples from statistical mechanics, genetics, population biology, epidemiology, and ecology. Some of our findings are only conjectures based on simulation, but in a number of cases we are able to prove results for systems with "fast stirring" by exploiting connections between the spatial model and an associated reaction diffusion equation.
A New Projection Method for Variational Inequality Problems
Authors: M. V. Solodov, B. F. Svaiter
Venue: SIAM Journal on Control and Optimization (1999)

We propose a new projection algorithm for solving the variational inequality problem, where the underlying function is continuous and satisfies a certain generalized monotonicity assumption (e.g., it can be pseudomonotone). The method is simple and admits a nice geometric interpretation. It consists of two steps. First, we construct an appropriate hyperplane which strictly separates the current iterate from the solutions of the problem. This procedure requires a single projection onto the feasible set and employs an Armijo-type linesearch along a feasible direction. Then the next iterate is obtained as the projection of the current iterate onto the intersection of the feasible set with the halfspace containing the solution set. Thus, in contrast with most other projection-type methods, only two projection operations per iteration are needed. The method is shown to be globally convergent to a solution of the variational inequality problem under minimal assumptions. Preliminary computational experience is also reported.
Matrix-Dependent Multigrid Homogenization for Diffusion Problems
Authors: S. Knapek
Venue: SIAM Journal on Scientific Computing (1998)

For problems with strongly varying or discontinuous diffusion coefficients we present a method to compute coarse-scale operators and to approximately determine the effective diffusion tensor on the coarse-scale level. The approach is based on techniques that are used in multigrid, such as matrix-dependent prolongations and the construction of coarse-grid operators by means of the Galerkin approximation. In numerical experiments we compare our multigrid-homogenization method with continuous homogenization, renormalization, and simple averaging approaches.
Efficient Methods for Out-of-Core Sparse Cholesky Factorization
Authors: Edward Rothberg, Robert Schreiber
Venue: SIAM Journal on Scientific Computing (1999)

We consider the problem of sparse Cholesky factorization with limited main memory. The goal is to efficiently factor matrices whose Cholesky factors essentially fill the available disk storage, using very little memory (as little as 16 Megabytes (MBytes)). This would enable very large industrial problems to be solved with workstations of very modest cost.We consider three candidate algorithms. Each is based on a partitioning of the matrix into panels. The first is a robust, out-of-core multifrontal method that keeps the factor, the stack, and the large frontal matrices on disk. The others are left-looking methods. We find that straightforward implementations of all of them suffer from excessive disk I/O for large problems that arise in interior-point algorithms for linear programming. We introduce several improvements to these simple out-of-core methods and find that a left-looking method that nevertheless uses the multifrontal algorithm for portions of the matrix (subtrees of the supernodal elimination tree whose multifrontal stack fits in memory) is very effective. With 32 Mbytes of main memory, it achieves over 77% of its in-core performance on all but one of our 12 test matrices (67% in that one case), even though the size of the factor is, in all cases, hundreds of millions or even billions of bytes.
Experience in implementing a document delivery service
Authors: Francesco Gennai, Laura Abba, Marina Buzzi, Maria G. Balestri, Silvana Mangiaracina
Venue: Proceedings of the fifth ACM conference on Digital libraries (2000)

In this paper we propose an integration between electronic mail and web services for people such as library operators who need to send large files to Internet users. The proposed solution permits libraries to continue using the e-mail service to send large documents, but at the same time overcomes problems that users can encounter downloading large size files with e-mail agents. The library operator sends the document as an attachment to the destination address, on fly the e-mail server extracts and saves the attachments in a web-server disk file and substitutes them with a new messsage part that includes the URL pointing to the saved document. The reciever can download these large objects using a user-friendly browser.
A Natural Approach to the Numerical Integration of Riccati Differential Equations
Authors: Jeremy Schiff, S. Shnider
Venue: SIAM Journal on Numerical Analysis (1999)

This paper introduces a new class of methods, which we call Möbius schemes, for the numerical solution of matrix Riccati differential equations. The approach is based on viewing the Riccati equation in its natural geometric setting, as a flow on the Grassmannian of m-dimensional subspaces of an (n+m)-dimensional vector space. Since the Grassmannians are compact differentiable manifolds, and the coefficients of the equation are assumed continuous, there are no singularities or intrinsic instabilities in the associated flow. The presence of singularities and numerical instabilities is an artifact of the coordinate system, but since Möbius schemes are based on the natural geometry, they are able to deal with numerical instability and pass accurately through the singularities. A number of examples are given to demonstrate these properties.
Potential of the GSM air interface to support CDMA operation
Authors: J. A. Pons Puig, J. Dunlop
Venue: Wireless Networks (2000)

The ongoing development of third generation systems sets the path for evolution of the existing second generation systems. Important issues are the need for compatibility and the establishment of a path of migration from the current operative mobile systems. This paper considers the feasibility of supporting CDMA capabilities within the GSM air interface in order to provide UMTS services. It produces performance estimates for two specific examples&colon; Joint Detection CDMA channels, and Multicarrier DS&dash;CDMA channels. It is shown that a number of advantages can be obtained by using a hybrid CDMA scheme.
A New Convergence Theorem for Successive Overrelaxation Iterations
Authors: A. J. Hughes Hallett, Laura Piscitelli
Venue: Computational Economics (1999)

This paper contains a new convergence theorem for Gauss-Seidel (SOR) iterations for an arbitrary equation system. We use that theorem to show how to reorder equations and to extend their radius of convergence. It is not generally optimal to minimise the number or size of the above diagonal elements in a non-recursive system.
The relevance of software education: A survey and some recommendations
Authors: Timothy C. Lethbridge
Venue: Annals of Software Engineering (1999)

We summarize the results of a survey of software practitioners in which we asked about the relevance of their education. We analyze the data and highlight potential changes to computer science or software engineering curricula, based on mismatches between the extent to which the topic is taught and its importance in the careers of the participants. We also present some advice to companies regarding topics in which they should train employees&semi; we compare this advice to a list of skills that employers have indicated they wish employees to possess.
Trace preconstruction
Authors: Quinn Jacobson, James E. Smith
Venue: Proceedings of the 27th annual international symposium on Computer architecture (2000)

Trace caches enable high bandwidth, low latency instruction supply, but have a high miss penalty and relatively large working sets. Consequently, their performance may suffer due to capacity and compulsory misses. Trace preconstruction augments a trace cache by performing a function analogous to prefetching. The trace preconstruction mechanism observes the processor's instruction dispatch stream to detect opportunities for jumping ahead of the processor. After doing so, the preconstruction mechanism fetches static instructions from the predicted future region of the program, and constructs a set of traces in advance of when they are needed. Trace preconstruction can significantly increase both the performance of the trace cache and the robustness of the trace cache to varying workloads. All but one of the SPECint95 benchmarks see a notable reduction in trace cache miss rates from preconstruction. The three benchmarks that have the largest working set (gee, go and vortex) see a 30% to 80% reduction in trace cache misses. We also consider the integration of preconstruction with another trace-specific mechanism (preprocessing) to produce a high performance frontend. When combined, preconstruction and trace preprocessing produce an average speedup of 14% for the SPECint95 benchmarks.
Designing virtual communities for work
Authors: Lori Toomey, Gloria Mark, John C. Tang, Lia Adams
Venue: ACM SIGGROUP Bulletin (1998)

While the popularity of networked virtual communities has been growing, their us has been mainly to engage in online socializing. Given the necessity of communication and collaboration among distributed workers, it seems natural to consider how these spaces might be used to support work and the surrounding social interactions. This collection of papers summarizes a workshop that was held at CSCW '98 that focused on understanding how organizations are currently using virtual communities, and how they could be enhanced to better support the needs of collaborative workers. By "virtual communities" we think primarily of MUDs, and other collaboration software involving some text, graphics, and/or other media. The workshop explored how to take advantage of the inherently engaging attributes of virtual communities to accomplish work, preserve organizational memory, promote corporate culture, and encourage professional networking. We identified issues that were common to the various groups exploring work-based virtual communities and shared the design approaches currently being tried out.
Hardware Implementation of a Pulse Density Neural Network Using Simultaneous Perturbation Learning Rule
Authors: Yutaka Maeda, Atsushi Nakazawa, Yakichi Kanata
Venue: Analog Integrated Circuits and Signal Processing (1999)

The choice of the learning scheme is very important in the implementation of neural networks to take advantage of their learning ability. Usually, the back-propagation method is widely used as a learning rule in neural networks. Since back-propagation requires so-called error back propagation to update weights, it is relatively difficult to realize hardware neural networks using the back-propagation method. In this paper, we present a pulse density neural network system with learning ability. As a learning rule, the simultaneous perturbation method is used. The learning rule requires only forward operations of networks to update weights instead of the error back-propaga- tion. Thus, we can construct the network system with learning ability without the need for a complicated circuit that calculates gradients of an error function. Pulse density is used to represent the basic quantities in this system. The pulse system has some attractive properties which includes robustness against a noisy environment. A combina- tion of the simultaneous perturbation learning rule and the pulse density system results in an interesting architec- ture of hardware neural systems. Results for the exclusive OR problem and a simple identity problem are shown.
Efficient geometry-based similarity search of 3D spatial databases
Authors: Daniel A. Keim
Venue: ACM SIGMOD Record (1999)

Searching a database of 3D-volume objects for objects which are similar to a given 3D search object is an important problem which arises in number of database applications &mdash; for example, in Medicine and CAD. In this paper, we present a new geometry-based solution to the problem of searching for similar 3D-volume objects. The problem is motivated from a real application in the medical domain where volume similarity is used as a basis for surgery decisions. Our solution for an efficient similarity search on large databases of 3D volume objects is based on a new geometric index structure. The basic idea of our new approach is to use the concept of hierarchical approximations of the 3D objects to speed up the search process. We formally show the correctness of our new approach and introduce two instantiations of our general idea, which are based on cuboid and octree approximations. We finally provide a performance evaluation of our new index structure revealing significant performance improvements over existing approaches.
Sequencing-by-hybridization at the information-theory bound: an optimal algorithm
Authors: Franco P. Preparata, Eli Upfal
Venue: Proceedings of the fourth annual international conference on Computational molecular biology (2000)

In a recent paper [PFU99) we have introduced a novel probing scheme for DNA sequencing by hybridization (SBH). The new gapped-probe scheme combines natural and universal bases in a well defined periodic pattern. It was shown in [PFU99] that the performance of the gapped-probe scheme (in terms of the length of a sequence that can be uniquely reconstructed using a given library size of probes) is significantly better than the standard scheme based on oligomer probes. In this paper we present and analyze a new, more powerful, sequencing algorithm for the gapped-probe scheme. We prove that the new algorithm exploits the full potential of the SBH technology with high-confidence performance, that comes within a small constant factor (about 2) of the information-theory bound. Moreover, this performance is achieved while maintaining running time linear in the target sequence length.
A Posteriori Finite Element Error Estimation for Diffusion Problems
Authors: Slimane Adjerid, Belkacem Belguendouz, Joseph E. Flaherty
Venue: SIAM Journal on Scientific Computing (1999)

Adjerid, Babuska, and Flaherty [ Math. Models Methods Appl. Sci., 9 (1999), pp. 261--286] and Yu [Math. Numer. Sinica, 13 (1991), pp. 89--101] and [Math. Numer. Sinica, 13 (1991), pp. 307--314] show that a posteriori estimates of spatial discretization errors of piecewise bi- p polynomial finite element solutions of elliptic and parabolic problems on meshes of square elements may be obtained from jumps in solution gradients at element vertices when p is odd and from local elliptic or parabolic problems when p is even. We show that these simple error estimates are asymptotically correct for other finite element spaces. The key requirement is that the trial space contain all monomial terms of degree p + 1 except for $ x_1^{p+1}$ and $ x_2^{p+1}$ in a Cartesian (x1,x2 ) frame. Computational results show that the error estimates are accurate, robust, and efficient for a wide range of problems, including some that are not supported by the present theory. These involve quadrilateral-element meshes, problems with singularities, and nonlinear problems.
Advanced CORBA programming with C++
Authors: Michi Henning, Steve Vinoski
Venue: Addison-Wesley Professional Computing Series (1999)

Here is the CORBA book that every C++ software engineer has been waiting for. Advanced CORBA® Programming with C++ provides designers and developers with the tools required to understand CORBA technology at the architectural, design, and source code levels. This book offers hands-on explanations for building efficient applications, as well as lucid examples that provide practical advice on avoiding costly mistakes. With this book as a guide, programmers will find the support they need to successfully undertake industrial-strength CORBA development projects.The content is systematically arranged and presented so the book may be used as both a tutorial and a reference. The rich example programs in this definitive text show CORBA developers how to write clearer code that is more maintainable, portable, and efficient. The authors' detailed coverage of the IDL-to-C++ mapping moves beyond the mechanics of the APIs to discuss topics such as potential pitfalls and efficiency. An in-depth presentation of the new Portable Object Adapter (POA) explains how to take advantage of its numerous features to create scalable and high-performance servers. In addition, detailed discussion of advanced topics, such as garbage collection and multithreading, provides developers with the knowledge they need to write commercial applications.Other highlights:In-depth coverage of IDL, including common idioms and design trade-offsComplete and detailed explanations of the Life Cycle, Naming, Trading, and Event ServicesDiscussion of IIOP and implementation repositoriesInsight into the dynamic aspects of CORBA, such as dynamic typing and the new DynAny interfacesAdvice on selecting appropriate application architectures and designsDetailed, portable, and vendor-independent source code
Twenty dirty tricks to train software engineers
Authors: Ray Dawson
Venue: Proceedings of the 22nd international conference on Software engineering (2000)

Many employers find that graduates and sandwich students come to them poorly prepared for the every day problems encountered at the workplace. Although many university students undertake team projects at their institutions, an education environment has limitations that prevent the participants experiencing the full range of problems encountered in the real world. To overcome this, action was taken on courses at the Plessey Telecommunications company and Loughborough University to disrupt the students' software development progress. These actions appear mean and vindictive, and are labeled 'dirty tricks' in this paper, but their value has been appreciated by both the students and their employers. The experiences and learning provided by twenty 'dirty tricks' are described and their contribution towards teaching essential workplace skills is identified. The feedback from both students and employers has been mostly informal but the universally favourable comments received give strong indications that the courses achieved their aim of preparing the students for the workplace. The paper identifies some limitations on the number and types of 'dirty tricks' that can be employed at a university and concludes that companies would benefit if such dirty tricks were employed in company graduate induction programmes as well as in university courses.
Bandwidth Management and Switch Buffer Allocation in High-speed Networks with Bursty Traffic
Authors: Anna Hać
Venue: International Journal of Network Management (1996)

This article proposes the bandwidth management algorithm that allows for packet transfer in the switch and admits packets based on the switch and network occupancy.
Pre-sampling as an approach for exploiting temporal uncertainty
Authors: Margaret L. Loper, Richard M. Fujimoto
Venue: Proceedings of the fourteenth workshop on Parallel and distributed simulation (2000)

In this paper we describe an approach to exploit temporal uncertainty in parallel and distributed simulation by utilizing time intervals rather than precise time stamps. Unlike previously published work that propose new message ordering semantics, our approach is based on conservative, time stamp order execution and enhancing the lookahead of the simulation by pre-drawing random numbers from a distribution that models temporal uncertainty. The advantages of this approach are that it allows time intervals to be exploited using a conventional Time Stamp Order (TSO) delivery mechanism, and it offers the modeler greater statistical control over the assigned time stamps. An implementation of this approach is described and initial performance measurements are presented.