ppxscal/embedding_network huggingface dataset:
Self-consistent Langevin simulation of Coulomb collisions in charged-particle beams
Authors: Ji Qiang, Robert D. Ryne, Salman Habib
Venue: Proceedings of the 2000 ACM/IEEE conference on Supercomputing (CDROM) (2000)

In many plasma physics and charged-particle beam dynamics problems, Coulomb collisions are modeled by a Fokker-Planck equation. In order to incorporate these collisions, we present a three-dimensional parallel Langevin simulation method using a Particle-In-Cell (PIC) approach implemented on high-performance parallel computers. We perform, for the first time, a fully self-consistent simulation, in which the friction and diffusion coefficients are computed from first principles. We employ a two-dimensional domain decomposition approach within a message passing programming paradigm along with dynamic load balancing. Object oriented programming is used to encapsulate details of the communication syntax as well as to enhance reusability and extensibility. Performance tests on the SGI Origin 2000, IBM SP RS/6000 and the Cray T3E-900 have demonstrated good scalability. As a test example, we demonstrate the collisional relaxation to a final thermal equilibrium of a beam with an initially ansiotropic velocity distribution.
Fast priority queues for cached memory
Authors: Peter Sanders
Venue: Journal of Experimental Algorithmics (JEA) (2000)

The cache hierarchy prevalent in todays high performance processors has to be taken into account in order to design algorithms that perform well in practice. This paper advocates the adaption of external memory algorithms to this purpose. This idea and the practical issues involved are exemplified by engineering a fast priority queue suited to external memory and cached memory that is based on <i>k</i>-way merging. It improves previous external memory algorithms by constant factors crucial for transferring it to cached memory. Running in the cache hierarchy of a workstation the algorithm is at least two times faster than an optimized implementation of binary heaps and 4-ary heaps for large inputs.
Comment on weighted increment linear search for scatter tables
Authors: S. K. Bandyopadhyay
Venue: Communications of the ACM (1977)

I would like to comment on an article by Fabrizio Luccio [1] which discusses weighted increment linear search for scatter tables.
Research issues in authorization models for hypertext systems
Authors: Elisa Bertino, Pierangela Samarati
Venue: Proceedings of the 1995 workshop on New security paradigms (1995)

The characteristics proper of hypertext systems, such as absence of schema, connections among the different &ldquo;chunks&rdquo; of information, possibility of navigating in the hypertext, make conventional authorization models not adequate for their protections. These characteristics, on one side raise new protection requirements, thus making the problem of protections much harder; on the other side, they provide a flexibility in the specification of authorizations greater than in more structured data models. We are currently working on an authorization model for the protection of information in distributed hypertext systems. In this paper we illustrate the new requirements that arise and discuss some of the issues we are currently investigating.
ARPA: a visible means of support
Authors: James P. Titus
Venue: Communications of the ACM (1967)

The Advanced Research Projects Agency has probably done more to lift computer science from other disciplines and to put it on its own feet than any organization inside or outside of government. Even today, when support of computing is spread throughout the government, ARPA is practically alone in its belief that computing deserves to be a separate discipline. Ironically, the computer profession knows little about this friendly benefactor.
Scheduling to reduce conflict in meetings
Authors: Joseph E. Grimes
Venue: Communications of the ACM (1970)

Conflicts in scheduling can be treated as defining an undirected linear graph independently of the relation of the activities in conflict to additional constraints of time and space. Each connected component of such a graph, which can be found by an algorithm described by Gotlieb and Corneil, corresponds to a set of events that must be scheduled at different times.
Documentation problems: ALGOL 60
Authors: Peter Naur
Venue: Communications of the ACM (1963)

In presenting the following notes I wish to make it clear that they express only my private views. Thus although these views naturally have been greatly influenced by the experience I have gained through my participation in the international ALGOL effort they do not represent the agreed opinion of any group and I alone should be held responsible for any misrepresentations.
Design and Evaluation of a Switch Cache Architecture for CC-NUMA Multiprocessors
Authors: Ravishankar R. Iyer, Laxmi N. Bhuyan
Venue: IEEE Transactions on Computers (2000)

Cache coherent nonuniform memory access (CC-NUMA) multiprocessors provide a scalable design for shared memory. But, they continue to suffer from large remote memory access latencies due to comparatively slow memory technology and large data transfer latencies in the interconnection network. In this paper, we propose a novel hardware caching technique, called switch cache, to improve the remote memory access performance of CC-NUMA multiprocessors. The main idea is to implement small fast caches in crossbar switches of the interconnect medium to capture and store shared data as they flow from the memory module to the requesting processor. This stored data acts as a cache for subsequent requests, thus reducing the need for remote memory accesses tremendously. The implementation of a cache in a crossbar switch needs to be efficient and robust, yet flexible for changes in the caching protocol. The design and implementation details of a CAche Embedded Switch ARchitecture, CAESAR, using wormhole routing with virtual channels is presented. We explore the design space of switch caches by modeling CAESAR in a detailed execution driven simulator and analyze the performance benefits. Our results show that the CAESAR switch cache is capable of improving the performance of CC-NUMA multiprocessors by up to 45 percent reduction in remote memory accesses for some applications. By serving remote read requests at various stages in the interconnect, we observe improvements in execution time as high as 20 percent for these applications. We conclude that switch caches provide a cost-effective solution for designing high performance CC-NUMA multiprocessors.
Parametric temporal logic for &ldquo;model measuring&rdquo;
Authors: Rajeev Alur, Kousha Etessami, Salvatore La Torre, Doron Peled
Venue: ACM Transactions on Computational Logic (TOCL) (2001)

We extend the standard model checking paradigm of linear temporal logic, LTL, to a &ldquo;model measuring&rdquo; paradigm where one can obtain more quantitative information beyond a &ldquo;Yes/No&rdquo; answer. For this purpose, we define a parametric temporal logic, PLTL, which allows statements such as &ldquo;a request p is followed in at most x steps by a response q,&rdquo; where x is a free variable. We show how one can, given a formula ***(x1...,xk) of PLTL and a system model K satisfies the property ***, but if so find valuations which satisfy various optimality criteria. In particular, we present algorithms for finding valuations which minimize (or maximize) the maximum (or minimum) of all parameters. Theses algorithms exhibit the same PSPACE complexity as LTL model checking. We show that our choice of syntax for PLTL lies at the threshold of decidability for parametric temporal logics, in that several natural extensions have undecidable &ldquo;model measuring&rdquo; problems.
Basis Norm Rescaling for Nonlinear Parameter Estimation
Authors: Kari Brusdal, Trond Mannseth
Venue: SIAM Journal on Scientific Computing (1999)

We consider the ill-posed, nonlinear problem of recovering the diffusion function in a one-dimensional elliptic equation. Previous work has revealed a correlation between high nonlinearity, low sensitivity, and short scale for this problem. It was noted that representing the unknown function by the multiscale Haar basis gave faster convergence than use of a local basis. The superior performance of the Haar basis was found to be related to the norms of the individual basis elements of this basis not being equal. The norm decreases with decreasing scale, enhancing the influence of parameters associated with low nonlinearity. Also, a hierarchical scale-by-scale approach was suggested to utilize the correlation between nonlinearity, scale, and sensitivity to increase the convergence speed of the parameter estimation. Through numerical experiments, we consider the effect of a systematic rescaling of the norms of the basis elements on the efficiency of the Broydon--Fletcher--Goldfarb--Shanno (BFGS) quasi-Newton minimization procedure. Norm rescaling is considered both for estimation of all parameters simultaneously, and for hierarchical scale-by-scale optimization.
Querying ATSQL databases with temporal logic
Authors: Jan Chomicki, David Toman, Michael H. Böhlen
Venue: ACM Transactions on Database Systems (TODS) (2001)

We establish a correspondence between temporal logic and a subset of ATSQL, a temporal extension of SQL-92. In addition, we provide an effective translation from temporal logic to ATSQL that enables a user to write high-level queries which are then evaluated against a space-efficient representation of the database. A reverse translation, also provided in this paper, characterizes the expressive power of a syntactically defined subset of ATSQL queries.
Creating and supporting learning environments
Authors: Igor Hawryszkiewycz
Venue: Proceedings of the Australasian conference on Computing education (2000)

The paper describes ways to create a variety of learning environments. It describes a metamodel for defining such environments and a system that implements the metamodel. The environments described include classroom teaching, group support, distance moderation and monitoring of groups. The paper then describes a system, called LiveNet [3], which can be used to configure a variety of learning environments in terms of the metamodel, and describes experiences in its use.
Toward automatic program synthesis
Authors: Zohar Manna, Richard J. Waldinger
Venue: Communications of the ACM (1971)

An elementary outline of the theorem-proving approach to automatic program synthesis is given, without dwelling on technical details. The method is illustrated by the automatic construction of both recursive and iterative programs operating on natural numbers, lists, and trees. In order to construct a program satisfying certain specifications, a theorem induced by those specifications is proved, and the desired program is extracted from the proof. The same technique is applied to transform recursively defined functions into iterative programs, frequently with a major gain in efficiency. It is emphasized that in order to construct a program with loops or with recursion, the principle of mathematical induction must be applied. The relation between the version of the induction rule used and the form of the program constructed is explored in some detail.
Power estimation of behavioral descriptions
Authors: F. Ferrandi, F. Fummi, E. Macii, M. Poncino, D. Sciuto
Venue: Proceedings of the conference on Design, automation and test in Europe (1998)

This paper presents a methodology for power estimation of designs described at the behavioral-level as the interconnection of functional modules. The input/output behavior of each module is implicitly stored using BDDs, and the power consumed by the network is estimated using a novel and accurate entropy-based approach. As a demonstration example, we have used the proposed power estimation technique to evaluate and compare the effects of some architectural transformations applied to a reference design specification on the power dissipation of the corresponding implementations.
Detection of Spurious Maxima through Random Draw Tests and Specification Tests
Authors: Robert E. Dorsey, Walter J. Mayer
Venue: Computational Economics (2000)

Consistent estimation requires finding the global maximum of some specified objective function. Local maxima are often easy to find, but do not necessarily yield consistent estimates. In many nonlinear applications, the researcher can rarely be certain that a found local maximum is global. This paper examines the ability of random draw tests and specification tests to detect spurious maxima. For random draw tests we analyze Veall (1990) and a test introduced here based on a generalized beta distribution. Specification tests routinely used by researchers are also examined as methods for detecting spurious maxima. Monte Carlo results are reported on various test functions. The results suggest that specification testa are more useful than the random draw tests for detecting spurious maxima.
Some new methods of detecting step edges in digital pictures
Authors: Bruce J. Schachter, Azriel Rosenfeld
Venue: Communications of the ACM (1978)

This note describes two operators that respond to step edges, but not to ramps. The first is similar to the digital Laplacian, but uses the max, rather than the sum, of the x and y second differences. The second uses the difference between the mean and median gray levels in a neighborhood. The outputs obtained from these operators applied to a set of test pictures are compared with each other and with the standard digital Laplacian and gradient. A third operator, which uses the distance between the center and centroid of a neighborhood as an edge value, is also briefly considered; it turns out to be equivalent to one of the standard digital approximations to the gradient.
A Fault-Tolerant Routing Scheme for Meshes with Nonconvex Faults
Authors: Chun-Lung Chen, Ge-Ming Chiu
Venue: IEEE Transactions on Parallel and Distributed Systems (2001)

In this paper, we propose a fault-tolerant routing scheme for meshes with solid faults. A flag bit is introduced for guiding misrouted messages. By fully utilizing virtual channels of each class, our algorithm uses only three virtual channels to ensure the property of deadlock freeness. Our scheme is able to handle solid faults whose associated fault rings overlap. In addition, the proposed algorithm can be used to route messages when fault regions touch the boundaries of the mesh.
Exploiting Wavefront Parallelism on Large-Scale Shared-Memory Multiprocessors
Authors: Naraig Manjikian, Tarek S. Abdelrahman
Venue: IEEE Transactions on Parallel and Distributed Systems (2001)

Wavefront parallelism, in which parallelism is limited to hyperplanes in an iteration space, can arise when compilers apply tiling to loop nests to enhance locality. Previous approaches for scheduling wavefront parallelism focused on maximizing parallelism, balancing workloads, and reducing synchronization. In this paper, we show that on large-scale shared-memory multiprocessors, locality is a crucial factor. We make the distinction between intratile and intertile locality and show that as the number of processors grows, intertile locality becomes more important. We consider and experimentally evaluate existing strategies for scheduling wavefront parallelism. We show that dynamic self-scheduling can be efficiently used on a small number of processors, but performs poorly at large scale because it does not enhance intertile locality. By contrast, static scheduling strategies enhance intertile locality for small tiles, maintaining parallelism and resulting in better performance at large scale. Results from a Convex SPP1000 multiprocessor demonstrate the importance of taking intertile locality into account. Static scheduling outperforms dynamic self-scheduling by a factor of up to 2.3 on 30 processors.
A snap-on placement tool
Authors: X. Yang, M. Wang, K. Eguro, M. Sarrafzadeh
Venue: Proceedings of the 2000 international conference on Computer-aided design (2001)

The standard cell placement problem has been extensively studied in the past twenty years. Many approaches were proposed and proven effective in practice. However, successful placement tools need enormous time in the course of development. In this paper we propose a new snap-on placement tool, which is based on multilevel hierarchical placement method. It has great flexibility to combine existing packages and techniques in its top-down framework. In addition, it can be used to build a good placement tool in a short amount of time. Some important issues in multilevel hierarchical placement are discussed here. We investigate the behavior of net-cut and wirelength objectives in global placement problem, propose a +??? level clustering technique and design a new top-down placement method based on partitioning, annealing and +??? level technique. We also work on the trade-off between solution quality and running time during the hierarchical placement. Experimental results show that strength of proposed placement tool, it produces very good results on all benchmarks and the best known result on the largest MCNC benchmark. (avql).
Automatic contour map
Authors: G. Cottafava, G. Le Moli
Venue: Communications of the ACM (1969)

Some methods for contour mapping by means of a digital plotter are dicussed, and a new method is presented that is simple enough to be implemented by programs with a rather small number of instructions (about 120 FORTRAN IV instructions are required). Comparisons with some methods proposed by other authors are also performed. A FORTRAN IV program implementing the proposed method is availabel at the Istituto di Elettrotecnica ed Elettronica, Politecnico di Milano.
Secure safe ambients
Authors: Michele Bugliesi, Giuseppe Castagna
Venue: ACM SIGPLAN Notices (2001)

Secure Safe Ambients (SSA) are a typed variant of Safe Ambients [9], whose type system allows behavioral invariants of ambients to be expressed and verified. The most significant aspect of the type system is its ability to capture both explicit and implicit process and ambient behavior: process types account not only for immediate behavior, but also for the behavior resulting from capabilities a process acquires during its evolution in a given context. Based on that, the type system provides for static detection of security attacks such as Trojan Horses and other combinations of malicious agents.We study the type system of SSA, define algorithms for type checking and type reconstruction, define powerful languages for expressing security properties, and study a distributed version of SSA and its type system. For the latter, we show that distributed type checking ensures security even in ill-typed contexts, and discuss how it relates to the security architecture of the Java Virtual Machine.
From service configuration through performance monitoring to fault detection: implementing an integrated and automated network maintenance platform for enhancing wide area transaction access services
Authors: Symeon Papavassiliou, Mike Pace
Venue: International Journal of Network Management (2000)

The design and implementation of integrated and automated network&ndash;service management platforms that can seamlessly configure services, monitor service&ndash;network performance, and detect network faults are of great importance and interest to the service and network providers. In this paper we describe a set of integrated Operations Support Systems &lpar;OSS&rpar; that implement proactive network maintenance process in Wide Area Transaction Access Services. Copyright &copy; 2000 John Wiley Sons, Ltd.
Phenotypical characterization of c-kit receptor deficient mouse femora using non-destructive high-resolution imaging techniques and biomechanical testing
Authors: E. D. Cindik, M. Maurer, M. K. Hannan, R. Müller, W. C. Hayes, L. Hovy, A. A. Kurth
Venue: Technology and Health Care (2000)

Objective: Pathological processes in bone can lead to fatal health consequences. Therefore, it is important to study factors that possibly influence the activity of bone cells. The mast cell is a normal component of bone, storing and producing many potent bioactive substances. One of the most important factors to influence mast cell number, function, and phenotype is the c-kit ligand. A defect of the c-kit receptor leads to mast cell deficiency. In literature oversight, evidence for the importance of mast cells in skeletal homeostasis is compiled. Methods: To investigate the influence of c-kit receptor deficiency on bone mass, geometry, microstructure, and strength, 30 femora of profoundly c-kit receptor deficient mouse mutants and 30 control group animals aged 8--20 weeks were phenotypically characterized using peripheral quantitative computed tomography (pQCT), micro-computed tomography (\muCT) and 3-point-bending. Results: The femora of the c-kit receptor and therefore mast cell deficient animals were significantly altered in bone mass and geometry but not in bone density and microstructure. The mutants had a lighter femur with a thinner shape. The lower load bearing capacity of the femora of mast cell deficient mouse mutants is more likely explained by the smaller amount of bone material than due to a change in intrinsic material properties. Technical considerations: With the little dimensions of mouse bones, it is of prime importance to have precise methods to phenotypically characterize the bone. The pQCT allows the separate assessment and analysis of trabecular and cortical bone density, as well as a statement about bone geometry. Beyond it, the \muCT-technique delivers a 3-D analysis of bone microstructure, which so far was only achieved with 2-D histomorphometry. \muCT is an efficient alternative to destructive histological preparations allowing further biomechanical testing of the same specimens to also deliver measures for bone strength.
A note on conditional expressions
Authors: Daniel P. Friedman, David S. Wise
Venue: Communications of the ACM (1978)

Evaluation of a conditional expression may succeed even when the &ldquo;deciding predicate&rdquo; diverges and the alternatives are records (or nodes) whose fields have different content.
Tight bounds for k-set agreement
Authors: Soma Chaudhuri, Maurice Erlihy, Nancy A. Lynch, Mark R. Tuttle
Venue: Journal of the ACM (JACM) (2000)

We prove tight bounds on the time needed to solve k-set agreement. In this problem, each processor starts with an arbitrary input value taken from a fixed set, and halts after choosing an output value. In every execution, at most k distinct output values may be chosen, and every processor's output value must be some processor's input value. We analyze this problem in a synchronous, message-passing model where processors fail by crashing. We prove a lower bound of f/k+1 degree of coordination required, and the number of faults tolerated, even in idealized models like the synchronous model. The proof of this result is interesting because it is the first to apply topological techniques to the synchronous model.