ppxscal/embedding_network huggingface dataset:
Efficient Fast Hartley Transform Algorithms for Hypercube-Connected Multicomputers
Authors: Cevdet Aykanat, Argun Derviş
Venue: IEEE Transactions on Parallel and Distributed Systems (1995)

Although fast Hartley transform (FHT) provides efficient spectral analysis of real discrete signals, the literature that addresses the parallelization of FHT is extremely rare. FHT is a real transformation and does not necessitate any complex arithmetics. On the other hand, FHT algorithm has an irregular computational structure which makes efficient parallelization harder. In this paper, we propose a efficient restructuring for the sequential FHT algorithm which brings regularity and symmetry to the computational structure of the FHT. Then, we propose an efficient parallel FHT algorithm for medium-to-coarse grain hypercube multicomputers by introducing a dynamic mapping scheme for the restructured FHT. The proposed parallel algorithm achieves perfect load-balance, minimizes both the number and volume of concurrent communications, allows only nearest-neighbor communications and achieves in-place computation and communication. The proposed algorithm is implemented on a 32-node iPSC/21 hypercube multicomputer. High-efficiency values are obtained even for small size FHT problems.Index Terms¿Digital signal processing, fast Hartley transform, parallel computing, multicomputer, hypercube, load balance, nearest-neighbor communication.
A Result Concerning Controllability for the Navier-Stokes Equations
Authors: E. Fernandez-Cara, M. Gonzalez-Burgos
Venue: SIAM Journal on Control and Optimization (1995)

The main goal of this paper is to present a new result concerning controllability of the time-dependent Navier-Stokes equations. Here, the control variable is the trace of the velocity field on a "small" part of the boundary. The main result states that the linear space spanned by final states is dense in the $L^2$ space of admissible fields. For the proof, one uses a duality argument that is suggested by the linear theory. This reduces the task to an existence/regularity result for a nonlinear problem.
Worlds to die for
Authors: Lane A. Hemaspaandra, Ajit Ramachandran, Marius Zimand
Venue: ACM SIGACT News (1995)

We last had an "open problems" column eighteen months ago [Hem94]. It contained seven problems. Of the seven, one has since been resolved (at least insofar as one can resolve the problem without outright collapsing complexity classes) in an exciting FOCS paper by Cai and Sivakumar ([CS95], see also [Ogi95b,CNS95]), and for another I received a proof via email unfortunately followed quickly by another email retracting the proof. Overall score:Mysteries of Complexity Theory: 6.Theoretical Computer Scientists:1.If you go to Atlantic City, you know which side to bet on! But be of good cheer. This issue's column contains a new list of open problems (though some favorites from the old list have stowed away here too). And to stack the deck in favor of theoretical computer scientists, the problems are posed quite obliquely. Rather than asking you to prove "X," many of the problems (e.g., Problems 2, 4, 5, 6, and 7) just ask you to show that "In some oracle world, X." Sound easy? Dig in! And if your attempt to find a world where X holds becomes too frustrating, don't hesitate to go for the real glory --- by proving that X fails in the real world (and every relativized world)!
Numerical analysis using nonprocedural paradigms
Authors: Stephen J. Sullivan, Benjamin G. Zorn
Venue: ACM Transactions on Mathematical Software (TOMS) (1995)

This article presents a survey on the innovative features of a handful of languages that offer new features that can be valuable in numerical analysis, and a survey of the pros and cons of the languages with regards to work in numerical analysis. Language features such as polymorphism, first-class functions, and object-oriented programming offer improved writability, readability, reliability, and maintenance of computer software. The article discusses language features and uses, and includes a comparison of current implementations. It is intended both as an introduction to nonprocedural language features for persons working in numerical mathematics and as an exploration of some of the language requirements of numerical mathematics for persons working in language development. The article discusses C++, Fortran 77, Fortran 90, Haskell, Lisp/CLOS, Modula-3, Sather, and SML with respect to a variety of numerical analysis tasks: interpolation, optimization, array access and update, iteration, recursion, random number generation, and Gaussian elimination on sparse matrices.
Dynamic Programming and Pricing of Contingent Claims in an Incomplete Market
Authors: Nicole El Karoui, Marie-Claire Quenez
Venue: SIAM Journal on Control and Optimization (1995)

The problem of pricing contingent claims or options from the price dynamics of certain securities is well understood in the context of a complete financial market. This paper studies the same problem in an incomplete market. When the market is incomplete, prices cannot be derived from the absence of arbitrage, since it is not possible to replicate the payoff of a given contingent claim by a controlled portfolio of the basic securities. In this situation, there is a price range for the actual market price of the contingent claim. The maximum and minimum prices are studied using stochastic control methods. The main result of this work is the determination that the maximum price is the smallest price that allows the seller to hedge completely by a controlled portfolio of the basic securities. A similar result is obtained for the minimum price (which corresponds to the purchase price).
Algorithm 749: fast discrete cosine transform
Authors: Barry G. Sherlock, Donald M. Monro
Venue: ACM Transactions on Mathematical Software (TOMS) (1995)

An in-place algorithm for the fast, direct computation of the forward and inverse discrete cosine transform is presented and evaluated. The transform length may be an arbitrary power of two.
Interrupts as threads
Authors: Steve Kleiman, Joe Eykholt
Venue: ACM SIGOPS Operating Systems Review (1995)

Most operating system implementations contain two fundamental forms of asynchrony; processes (or equivalently, internal threads) and interrupts. Processes (or threads) synchronize using primitives such as mutexes and condition variables, while interrupts are synchronized by preventing their occurrence for a period of time. The latter technique not only is expensive, but it locks out interrupts on the possibility that an interrupt will occur and interfere with the particular critical section of code that was interrupted.In the Solaris 2 implementation of UNIX [Eykholt 92] [Kleiman 92], these two forms are unified into a single model, threads. Interrupts are converted into threads using a low overhead technique. This allows a single synchronization model to be used throughout the kernel. In addition, it lowers the number of times in which interrupts are locked out, it removes the overhead of masking interrupts, and allows modular code to be oblivious to the interrupt level it is called at.
Parallel linear general relativity and CMB anisotropies
Authors: Paul Bode, Edmund Bertschinger
Venue: Proceedings of the 1995 ACM/IEEE conference on Supercomputing (CDROM) (1995)

We have developed a code which links the primeval fluctuations in the early universe with those observable at the present time by integrating the coupled, linearized, Einstein, Boltzmann, and fluid equations governing the evolution of metric perturbations and density fluctuations; this is the most accurate treatment to date of both the physics and the numerical integration. The results are useful both for calculations of the cosmic microwave background (CMB) anisotropy and the linear power spectrum of matter fluctuations. The serial code (LINGER) is highly efficient on vector machines. Furthermore, this application is perfectly suited for coarse-grained parallelism. A portable, parallel implementation (PLINGER) using common message-passing libraries (PVM, MPI, MPL, and PVMe) has been completed; it achieves Gflop/sec rates on current parallel supercomputers such as the T3D and SP2. LINGER and PLINGER are publically available as part of the COSMICS software package.
The semantics of Scheme with future
Authors: Luc Moreau
Venue: ACM SIGPLAN Notices (1996)

We present the formal semantics of future in a Scheme-like language which has both side-effects and first-class continuations. Correctness is established by proving that programs annotated by future have the same observable behaviour as their non-annotated counterparts, even though evaluation may be parallel.
Assessing computer security vulnerability
Authors: Jim Alves-Foss, Salvador Barbosa
Venue: ACM SIGOPS Operating Systems Review (1995)

The lack of a standard gauge for quantifying computer system vulnerability is a hindrance to communicating information about vulnerabilities, and is thus a hindrance to reducing those vulnerabilities. The inability to address this issue through uniform semantics often leads to uncoordinated efforts at combating exposure to common avenues of exploitation. The de-facto standard for evaluating computer security is the government's Trusted Computer Evaluation Criteria, also known as the Orange Book. However, it is a generally accepted fact that the majority of non-government multi-user computer systems are classified into one of its two lower classes. The link between the higher classes and government classified data, makes the measure unsuitable for commercial use.This project presents a feasible approach for resolving this problem by introducing a standardized assessment. It introduces a method, termed the System Vulnerability Index (SVI), that analyzes a number of factors that affect security. These factors are evaluated and combined, through the use of special rules, to provide a measure of vulnerability. The strength of this method is in its abstraction of the problem, which makes it applicable to various operating systems and hardware implementations. User and superuser actions, as well as clues to a potentially breached state of security, serve as the basis for the security relevant factors. Facts for assessment are presented in a form suitable for implementation in a rule-based expert system.
On the shortest paths between two convex polyhedra
Authors: Avikam Balstan, Micha Sharir
Venue: Journal of the ACM (JACM) (1988)

The problem of computing the Euclidean shortest path between two points in three-dimensional space bounded by a collection of convex and disjoint polyhedral obstacles having n faces altogether is considered. This problem is known to be NP-hard and in exponential time for arbitrarily many obstacles; it can be solved in O(n2log n) time for a single convex polyhedral obstacle and in polynomial time for any fixed number of convex obstacles. In this paper Mount's technique is extended to the case of two convex polyhedral obstacles and an algorithm that solves this problem in time O(n3 &middot; 2O{&agr;(n)4}log n) (where &agr;(n) is the functional inverse of Ackermann's function, and is thus extremely slowly growing) is presented, thus improving significantly Sharir's previous results for this special case. This result is achieved by constructing a new kind of Voronoi diagram, called peeper's Voronoi diagram, which is introduced and analyzed in this paper, and which may be of interest in its own right.
Safety as a system property
Authors: Nancy G. Leveson
Venue: Communications of the ACM (1995)

When computers are used to control potentially dangerous devices, new issues and concerns are raised for software engineering. Simply focusing on building software that matches its specifications is not enough. Accidents occur even when the individual system components are highly reliable and have not &ldquo;failed.&rdquo; That is, accidents in complex systems often arise in the interactions among the system components, each one operating according to its specified behavior but together creating a hazardous system state.
LeRec: a NN/HMM hybrid for on-line handwriting recognition
Authors: Yoshua Bengio, Yann LeCun, Craig Nohl, Chris Burges
Venue: Neural Computation (1995)

We introduce a new approach for on-line recognition of handwritten words written in unconstrained mixed style. The preprocessor performs a word-level normalization by fitting a model of the word structure using the EM algorithm. Words are then coded into low resolution "annotated images" where each pixel contains information about trajectory direction and curvature. The recognizer is a convolution network that can be spatially replicated. From the network output, a hidden Markov model produces word scores. The entire system is globally trained to minimize word-level errors.
An $\cal NC$ Algorithm for Evaluating Monotone Planar Circuits
Authors: A. L. Delcher, S. Rao Kosaraju
Venue: SIAM Journal on Computing (1995)

Goldschlager first established that a special case of the monotone planar circuit problem can be solved by a Turing machine in $O(\log^2 n)$ space. Subsequently, Dymond and Cook refined the argument and proved that the same class can be evaluated in $O(\log^2 n)$ time with a polynomial number of processors. In this paper, we prove that the general monotone planar circuit value problem can be evaluated in $O(\log^4 n)$ time with a polynomial number of processors, settling an open problem posed by Goldschlager and Parberry.
Tough Ramsey Graphs Without Short Cycles
Authors: Noga Alon
Venue: Journal of Algebraic Combinatorics: An International Journal (1995)

A graph G is t-tough if any induced subgraph of it with x > 1 connected components is obtained from G by deleting at least tx vertices. It is shown that for every t and g there are t-tough graphs of girth strictly greater than g. This strengthens a recent result of Bauer, van den Heuvel and Schmeichel who proved the above for g &equals; 3, and hence disproves in a strong sense a conjecture of Chv&aacute;tal that there exists an absolute constant t0 so that every t0-tough graph is pancyclic. The proof is by an explicit construction based on the tight relationship between the spectral properties of a regular graph and its expansion properties. A similar technique provides a simple construction of triangle-free graphs with independence number m on &Omega;(m4/3) vertices, improving previously known explicit constructions by Erd&ouml;s and by Chung, Cleve and Dagum.
ParaSol: a multithreaded system for parallel simulation based on mobile threads
Authors: Edward Mascarenhas, Felipe Knop, Vernon Rego
Venue: Proceedings of the 27th conference on Winter simulation (1995)

ParaSol is a novel multithreaded system for shared-and distributed-memory parallel simulation, designed to support a variety of domain-specific simulation object libraries. We report on the design of the ParaSol kernel, which drives executions based on optimistic and adaptive synchronization protocols. The active-transaction flow methodology we advocate is enabled by an underlying, efficient lightweight process system. Though this process- and object-interaction view is known to both simplify and speed transition from model design to simulation implementation, migratable threads and objects pose many serious challenges to efficient kernel operation. Good solutions to these challenging problems are key to good simulator performance. We present techniques for the support of optimistic parallel simulations, addressing synchronization, state-saving, rollback, inter-process communication, and process scheduling.
The Graz digital library effort
Authors: H. Maurer
Venue: ACM SIGWEB Newsletter (1995)

Tile Graz Digital Library effort is based on an extension of WWW, the "first second generation hypermedia system" Hyper-G. The reason for choosing Hyper-G is that it not only supports all kinds of searches, but allows to define arbitrary scopes for searches, tlnat it supports multitinguality and that, due to its link concept, allows to (a) conduct discussions around any part of any document and (b) allows to customize the data base for personal purposes. For more information on Hyper-G see http://hyperg.iicm.tu-graz.ac.at.
Evaluating The Mediator Method: Prism as a Case Study
Authors: Kevin J. Sullivan, Ira J. Kalet, David Notkin
Venue: IEEE Transactions on Software Engineering (1996)

A software engineer's confidence in the profitability of a novel design technique depends to a significant degree on previous demonstrations of its profitability in practice. Trials of proposed techniques are thus of considerable value in providing factual bases for evaluation. In this paper we present our experience with a previously presented design approach as a basis for evaluating its promise and problems. Specifically, we report on our use of the mediator method to reconcile tight behavioral integration with ease of development and evolution of Prism, a system for planning radiation treatments for cancer patients. Prism is now in routine clinical use in several major research hospitals. Our work supports two claims. In comparison to more common design techniques, the mediator approach eases the development and evolution of integrated systems; and the method can be learned and used profitably by practicing software engineers.
Coherent network interfaces for fine-grain communication
Authors: Shubhendu S. Mukherjee, Babak Falsafi, Mark D. Hill, David A. Wood
Venue: Proceedings of the 23rd annual international symposium on Computer architecture (1996)

Historically, processor accesses to memory-mapped device registers have been marked uncachable to insure their visibility to the device. The ubiquity of snooping cache coherence, however, makes it possible for processors and devices to interact with cachable, coherent memory operations. Using coherence can improve performance by facilitating burst transfers of whole cache blocks and reducing control overheads (e.g., for polling).This paper begins an exploration of network interfaces (NIs) that use coherence---coherent network interfaces (CNIs)---to improve communication performance. We restrict this study to NI/CNIs that reside on coherent memory or I/O buses, to NI/CNIs that are much simpler than processors, and to the performance of fine-grain messaging from user process to user process.Our first contribution is to develop and optimize two mechanisms that CNIs use to communicate with processors. A cachable device register---derived from cachable control registers [39,40]---is a coherent, cachable block of memory used to transfer status, control, or data between a device and a processor. Cachable queues generalize cachable device registers from one cachable, coherent memory block to a contiguous region of cachable, coherent blocks managed as a circular queue.Our second contribution is a taxonomy and comparison of four CNIs with a more conventional NI. Microbenchmark results show that CNIs can improve the round-trip latency and achievable bandwidth of a small 64-byte message by 37% and 125% respectively on the memory bus and 74% and 123% respectively on a coherent I/O bus. Experiments with five macrobenchmarks show that CNIs can improve the performance by 17-53% on the memory bus and 30-88% on the I/O bus.
Bounds on information exchange for Byzantine agreement
Authors: Danny Dolev, Rüdiger Reischuk
Venue: Journal of the ACM (JACM) (1985)

Byzantine Agreement has become increasingly important in establishing distributed properties when errors may exist in the systems. Recent polynomial algorithms for reaching Byzantine Agreement provide us with feasible solutions for obtaining coordination and synchronization in distributed systems. In this paper the amount of information exchange necessary to ensure Byzantine Agreement is studied. This is measured by the total number of messages the participating processors have to send in the worst case. In algorithms that use a signature scheme, the number of signatures appended to messages are also counted. First it is shown that &OHgr;(nt) is a lower bound for the number of signatures for any algorithm using authentication, where n denotes the number of processors and t the upper bound on the number of faults the algorithm is supposed to handle. For algorithms that reach Byzantine Agreement without using authentication this is even a lower bound for the total number of messages. If n is large compared to t, these bounds match the upper bounds from previously known algorithms. For the number of messages in the authenticated case we prove the lower bound &OHgr;(n + t2). Finally algorithms that achieve this bound are presented.
Parallel algorithms for image histogramming and connected components with an experimental study (extended abstract)
Authors: David A. Bader, Joseph JáJá
Venue: Proceedings of the fifth ACM SIGPLAN symposium on Principles and practice of parallel programming (1995)

This paper presents efficient and portable implementations of two useful primitives in image processing algorithms, histogramming and connected components. Our general framework is a single-address space, distributed memory programming model. We use efficient techniques for distributing and coalescing data as well as efficient combinations of task and data parallelism. Our connected components algorithm uses a novel approach for parallel merging which performs drastically limited updating during iterative steps, and concludes with a total consistency update at the final step. The algorithms have been coded in Split-C and run on a variety of platforms. Our experimental results are consistent with the theoretical analysis and provide the best known execution times for these two primitives, even when compared with machine-specific implementations. More efficient implementations of Split-C will likely result in even faster execution times.
Browsing and querying in online documentation: a study of user interfaces and the interaction process
Authors: Morten Hertzum, Erik Frøkjær
Venue: ACM Transactions on Computer-Human Interaction (TOCHI) (1996)

A user interface study concerning the usage effectiveness of selected retrieval modes was conducted using an experimental text retrieval system, TeSS, giving access to online documentation of certain programming tools. Four modes of TeSS were compared: (1) browsing, (2) conventional boolean retrieval, (3) boolean retrieval based on Venn diagrams, and (4) these three combined. Further, the modes of TeSS were compared to the use of printed manuals. The subjects observed were 87 computing new to them. In the experiment the use of printed manuals is faster and provides answers of higher quality than any of the electronic modes. Therefore, claims about the effectiveness of computer-based text retrieval have to by vary in situations where printed manuals are manageable to the user. Among the modes of TeSS, browsing is the fastest and the one causing the fewest operational errors. On the same two variables, time and operational errors, the Venn diagram mode performs better than conventional boolean retrieval. The combined mode scores worst on the objective performance measures; nonetheless nearly all subject prefer this mode. Concerning the interaction process, the subjects tend to manage the complexities of the information retrieval tasks by issuing series of simple commands and exploiting the interactive capabilities of TeSS. To characterize the dynamics of the interaction process two concepts are introduced; threads and sequences of tactics. Threads in a query sequence describes the continuity during retrieval. Sequences of tactics concern the combined mode and describe how different retrieval modes succeed each other as the retrieval process evolves.