ppxscal/embedding_network huggingface dataset:
Systems reengineering patterns
Authors: Perdita Stevens, Rob Pooley
Venue: Proceedings of the 6th ACM SIGSOFT international symposium on Foundations of software engineering (1998)

The reengineering of legacy systems --- by which we mean those that have value and yet "significantly resist modification and evolution to meet new and constantly changing business requirements" --- is widely recognised as one of the most significant challenges facing software engineers. The problem is widespread, affecting all kinds of organisations; serious, as failure to reengineer can hamper an organisation's attempts to remain competitive; and persistent, as there seems no reason to be confident that today's new systems are not also tomorrow's legacy systems.This paper argues1. that the main problem is not that the necessary expertise does not exist, but rather, that it is hard for software engineers to become expert;2. that the diversity of the problem domain poses problems for conventional methodological approaches;3. that an approach via systems reengineering patterns can help.We support our contention by means of some candidate patterns drawn from our own experience and published work on reengineering. We discuss the scope of the approach, how work in this area can proceed, and in particular how patterns may be identified and confirmed.
A Multistrategy Approach to Relational Knowledge Discovery inDatabases
Authors: Katharina Morik, Peter Brockhausen
Venue: Machine Learning (1997)

When learning from very large databases, the reduction of complexity is extremely important. Two extremes of making knowledge discovery in databases (KDD) feasible have been put forward. One extreme is to choose a very simple hypothesis language, thereby being capable of very fast learning on real-world databases. The opposite extreme is to select a small data set, thereby being able to learn very expressive (first-order logic) hypotheses. A multistrategy approach allows one to include most of these advantages and exclude most of the disadvantages. Simpler learning algorithms detect hierarchies which are used to structure the hypothesis space for a more complex learning algorithm. The better structured the hypothesis space is, the better learning can prune away uninteresting or losing hypotheses and the faster it becomes.We have combined inductive logic programming (ILP) directly with a relational database management system. The ILP algorithm is controlled in a model-driven way by the user and in a data-driven way by structures that are induced by three simple learning algorithms.
Beyond the flow decomposition barrier
Authors: Andrew V. Goldberg, Satish Rao
Venue: Journal of the ACM (JACM) (1998)

We introduce a new approach to the maximum flow problem. This approach is based on assigning arc lengths based on the residual flow value and the residual arc capacities. Our approach leads to an O(min(n2/3, m1/2)m log(n2/m) log U) time bound for a network with n vertices, m arcs, and integral arc capacities in the range [1, &hellip;, U]. This is a fundamental improvement over the previous time bounds. We also improve bounds for the Gomory-Hu tree problem, the parametric flow problem, and the approximate s-t cut problem.
Statistical estimation of the cumulative distribution function for power dissipation in VLSI cirucits
Authors: Chih-Shun Ding, Qing Wu, Chen-Ta Hsieh, Massoud Pedram
Venue: Proceedings of the 34th annual Design Automation Conference (1997)

This paper proposes to use quantile points of the cumulative distributionfunction for power consumption to provide detailed informationabout the power distribution in a circuit. The paper also presentstwo techniques based on population pruning and stratification to improvethe efficiency of estimation. Both population pruning and stratificationare based on a lowcost predictor, such as zero-delay powerestimate. Experimental results show the effectiveness of the proposedtechniques in providing detailed power distribution information.
Comments on &ldquo;a reduced test suite for protocol conformance testing&rdquo;
Authors: Alexandre Petrenko
Venue: ACM Transactions on Software Engineering and Methodology (TOSEM) (1997)

A previousACM TOSEM article of Ph. Bernhard (&ldquo;A Reduced Test Suite of Protocol Conformance Testing,&rdquo; ACM Transactions on Software Engineering and Methodology, Vol. 3, No. 3, July 1994, pages 201-220) describes three new versions of the so-called W-method for solving the protocol-testing problem, i.e., solving the Mealy machine equivalence problem. The author claims that these versions all have the same fault detection capability as the original W-method. In this correspondence we prove that the results of that article are incorrect.
Deterministic Voting in Distributed Systems Using Error-Correcting Codes
Authors: Lihao Xu, Jehoshua Bruck
Venue: IEEE Transactions on Parallel and Distributed Systems (1998)

Distributed voting is an important problem in reliable computing. In an N Modular Redundant (NMR) system, the N computational modules execute identical tasks and they need to periodically vote on their current states. In this paper, we propose a deterministic majority voting algorithm for NMR systems. Our voting algorithm uses error-correcting codes to drastically reduce the average case communication complexity. In particular, we show that the efficiency of our voting algorithm can be improved by choosing the parameters of the error-correcting code to match the probability of the computational faults. For example, consider an NMR system with 31 modules, each with a state of m bits, where each module has an independent computational error probability of 10¿3. In this NMR system, our algorithm can reduce the average case communication complexity to approximately 1.0825m compared with the communication complexity of 31m of the naive algorithm in which every module broadcasts its local result to all other modules. We have also implemented the voting algorithm over a network of workstations. The experimental performance results match well the theoretical predictions.
Code compression
Authors: Jens Ernst, William Evans, Christopher W. Fraser, Todd A. Proebsting, Steven Lucco
Venue: ACM SIGPLAN Notices (1997)

Current research in compiler optimization counts mainly CPU time and perhaps the first cache level or two. This view has been important but is becoming myopic, at least from a system-wide viewpoint, as the ratio of network and disk speeds to CPU speeds grows exponentially.For example, we have seen the CPU idle for most of the time during paging, so compressing pages can increase total performance even though the CPU must decompress or interpret the page contents. Another profile shows that many functions are called just once, so reduced paging could pay for their interpretation overhead.This paper describes: bull; Measurements that show how code compression can save space and total time in some important real-world scenarios. bull; A compressed executable representation that is roughly the same size as gzipped x86 programs and can be interpreted without decompression. It can also be compiled to high-quality machine code at 2.5 megabytes per second on a 120MHz Pentium processor bull; A compressed "wire" representation that must be decompressed before execution but is, for example, roughly 21% the size of SPARC code when compressing gcc.
A method for parallel program generation with an application to the Booster language
Authors: Edwin M. Paalvast, Arjan J. van Gemund, Henk J. Sips
Venue: Proceedings of the 4th international conference on Supercomputing (1990)

This paper describes a translation method for the automatic parallelization of programs based on a separately specified representation of the data. The method unifies the concept of data-representation on the algorithm-level as well as machine-level, based on the so-called view concept. It is shown that given a decomposition of the data, application of the translation method to the view-based Booster programming language results in efficient SPMD-code for distributed- as well as shared-memory architectures. It will be argued that the method is not restricted to Booster, but can also be applied to other languages.
Network performance effects of HTTP/1.1, CSS1, and PNG
Authors: Henrik Frystyk Nielsen, James Gettys, Anselm Baird-Smith, Eric Prud'hommeaux, Håkon Wium Lie, Chris Lilley
Venue: ACM SIGCOMM Computer Communication Review (1997)

We describe our investigation of the effect of persistent connections, pipelining and link level document compression on our client and server HTTP implementations. A simple test setup is used to verify HTTP/1.1's design and understand HTTP/1.1 implementation strategies. We present TCP and real time performance data between the libwww robot [27] and both the W3C's Jigsaw [28] and Apache [29] HTTP servers using HTTP/1.0, HTTP/1.1 with persistent connections, HTTP/1.1 with pipelined requests, and HTTP/1.1 with pipelined requests and deflate data compression [22]. We also investigate whether the TCP Nagle algorithm has an effect on HTTP/1.1 performance. While somewhat artificial and possibly overstating the benefits of HTTP/1.1, we believe the tests and results approximate some common behavior seen in browsers. The results confirm that HTTP/1.1 is meeting its major design goals. Our experience has been that implementation details are very important to achieve all of the benefits of HTTP/1.1.For all our tests, a pipelined HTTP/1.1 implementation outperformed HTTP/1.0, even when the HTTP/1.0 implementation used multiple connections in parallel, under all network environments tested. The savings were at least a factor of two, and sometimes as much as a factor of ten, in terms of packets transmitted. Elapsed time improvement is less dramatic, and strongly depends on your network connection.Some data is presented showing further savings possible by changes in Web content, specifically by the use of CSS style sheets [10], and the more compact PNG [20] image representation, both recent recommendations of W3C. Time did not allow full end to end data collection on these cases. The results show that HTTP/1.1 and changes in Web content will have dramatic results in Internet and Web performance as HTTP/1.1 and related technologies deploy over the near future. Universal use of style sheets, even without deployment of HTTP/1.1, would cause a very significant reduction in network traffic.This paper does not investigate further performance and network savings enabled by the improved caching facilities provided by the HTTP/1.1 protocol, or by sophisticated use of range requests.
Performance issues of enterprise level web proxies
Authors: Carlos Maltzahn, Kathy J. Richardson, Dirk Grunwald
Venue: Proceedings of the 1997 ACM SIGMETRICS international conference on Measurement and modeling of computer systems (1997)

Enterprise level web proxies relay world-wide web traffic between private networks and the Internet. They improve security, save network bandwidth, and reduce network latency. While the performance of web proxies has been analyzed based on synthetic workloads, little is known about their performance on real workloads. In this paper we present a study of two web proxies (CERN and Squid) executing real workloads on Digital's Palo Alto Gateway. We demonstrate that the simple CERN proxy architecture outperforms all but the latest version of Squid and continues to outperform cacheless configurations. For the measured load levels the Squid proxy used at least as many CPU, memory, and disk resources as CERN, in some configurations significantly more resources. At higher load levels the resource utilization requirements will cross and Squid will be the one using fewer resources. Lastly we found that cache hit rates of around 30% had very little effect on the requests service time.
Exploiting off-chip memory access modes in high-level synthesis
Authors: Preeti Ranjan Panda, Nikil D. Dutt, Alexandru Nicolau
Venue: Proceedings of the 1997 IEEE/ACM international conference on Computer-aided design (1997)

Memory-intensive behaviors often contain large arrays that are synthesized into off-chip memories. With the increasing gap between on-chip and off-chip memory access delays, it is imperative to exploit the efficient access mode features of modern-day memories (e.g., page-mode DRAMs) in order to alleviate the memory bandwidth bottleneck. Our work addresses this issue by: (a) modeling realistic off-chip memory access modes for High-Level Synthesis (HLS), (b) presenting algorithms to infer applicability of HLS with these memory access modes, and (c) transforming input behavior to provide further memory access optimizations during HLS. We demonstrate the utility of our approach using a suite of memory-intensive benchmarks with a realistic DRAM library module. Experimental results show a significant performance improvement (more than 40\%) as a result of our optimization techniques.
Parallel Execution of Hash Joins in Parallel Databases
Authors: Hui-I Hsiao, Ming-Syan Chen, Philip S. Yu
Venue: IEEE Transactions on Parallel and Distributed Systems (1997)

In this paper, we explore two important issues, processor allocation and the use of hash filters, to improve the parallel execution of hash joins. To exploit the opportunity of pipelining for hash join execution, a scheme to transform a bushy execution tree to an allocation tree is first devised. In an allocation tree, each node denotes a pipeline. Then, using the concept of synchronous execution time, processors are allocated to the nodes in the allocation tree in such a way that inner relations in a pipeline can be made available at approximately the same time. Also, the approach of hash filtering is investigated to further improve the parallel execution of hash joins. Extensive performance studies are conducted via simulation to demonstrate the importance of processor allocation and to evaluate various schemes using hash filters. It is experimentally shown that processor allocation is, in general ,the dominant factor to performance, and the effect of hash filtering becomes more prominent as the number of relations in a query increases.
Simulation: &ldquo;What to do with the model afterward&rdquo;
Authors: Daniel J. Muller
Venue: Proceedings of the 28th conference on Winter simulation (1996)

Once the simulation analysis is completed, what becomes of the simulation model? Often all the efforts and costs incurred during the simulation project are forgotten once the results of the simulation are determined. Simulation models can have a second life, in which they provide training, educating, and the means to assist the decision making process. Although simulation projects often involve the key individuals necessary for defining, analyzing, and evaluating the simulation models, they often overlook the individuals whom the simulation results will greatly impact. This paper discusses the need for education in the simulation process and some approaches for structuring models to be used for training and educational use.
A Comparative Analysis of Methods for Pruning Decision Trees
Authors: Floriana Esposito, Donato Malerba, Giovanni Semeraro
Venue: IEEE Transactions on Pattern Analysis and Machine Intelligence (1997)

In this paper, we address the problem of retrospectively pruning decision trees induced from data, according to a top-down approach. This problem has received considerable attention in the areas of pattern recognition and machine learning, and many distinct methods have been proposed in literature. We make a comparative study of six well-known pruning methods with the aim of understanding their theoretical foundations, their computational complexity, and the strengths and weaknesses of their formulation. Comments on the characteristics of each method are empirically supported. In particular, a wide experimentation performed on several data sets leads us to opposite conclusions on the predictive accuracy of simplified trees from some drawn in the literature. We attribute this divergence to differences in experimental designs. Finally, we prove and make use of a property of the reduced error pruning method to obtain an objective evaluation of the tendency to overprune/underprune observed in each method.
Task-wait-for graphs and their application to handling tasking deadlocks
Authors: Jingde Cheng
Venue: Proceedings of the conference on TRI-ADA '90 (1990)

A formal representation of the state of tasking object interaction in concurrent Ada programs is indispensable in order to handle tasking deadlocks occurring in the programs correctly. This paper presents a formal model, named &ldquo;Task-Wait-For Graphs&rdquo;, for the state of tasking object interaction and shows its application to handling tasking deadlocks. After defining the model and showing its basic properties, the paper gives a complete classification for tasking deadlocks, shows necessary and sufficient conditions for occurrences of these tasking deadlocks, points out that none of tasking deadlock detection methods proposed in recent years is correct in the sense of detecting all tasking deadlocks in any Ada program, and discusses how to detect the tasking deadlocks correctly based on the model.
Adaptive TTL schemes for load balancing of distributed Web servers
Authors: Michele Colajanni, Philip S. Yu
Venue: ACM SIGMETRICS Performance Evaluation Review (1997)

With ever increasing web traffic, a distributed Web system can provide scalability and flexibility to cope with growing client demands. Load balancing algorithms to spread the load across multiple Web servers are crucial to achieve the scalability. Various domain name server (DNS) based schedulers have been proposed in the literature, mainly for multiple homogeneous servers. DNS provides (logical) host name to IP-address mapping (i.e., the server assignment), but the mapping is not done for each server access. This is because the address mapping is cached for a time-to-live (TTL) period to reduce network traffic. The presence of heterogeneous Web servers not only increases the complexity of the DNS scheduling problem, but also makes previously proposed algorithms for homogeneous distributed systems such as round robin not directly applicable. This leads us to propose new policies, called adaptive TTL algorithms, that take both the uneven distribution of client request rates and heterogeneity of Web servers into account to adaptively set the TTL value for each address mapping request. Extensive simulation results show that these strategies are effective in balancing load among geographically distributed heterogeneous Web servers.
Heterogeneous Simulation&mdash;Mixing Discrete-Event Models with Dataflow
Authors: Wan-Teh Chang, Soonhoi Ha, Edward A. Lee
Venue: Journal of VLSI Signal Processing Systems (1997)

This paper relates to system-level design of signal processing systems, which are often heterogeneous in implementation technologies and design styles. The heterogeneous approach, by combining small, specialized models of computation, achieves generality and also lends itself to automatic synthesis and formal verification. Key to the heterogeneous approach is to define interaction semantics that resolve the ambiguities when different models of computation are brought together. For this purpose, we introduce a tagged signal model as a formal framework within which the models of computation can be precisely described and unambiguously differentiated, and their interactions can be understood. In this paper, we will focus on the interaction between dataflow models, which have partially ordered events, and discrete-event models, with their notion of time that usually defines a total order of events. A variety of interaction semantics, mainly in handling the different notions of time in the two models, are explored to illustrate the subtleties involved. An implementation based on the Ptolemy system from U.C. Berkeley is described and critiqued.
Domain Decomposition using Spectral Expansions of Steklov--Poincaré Operators II: A Matrix Formulation
Authors: Ramesh Natarajan
Venue: SIAM Journal on Scientific Computing (1997)

We describe a matrix formulation of the iterative domain decomposition method in Natarajan [SIAM J. Sci. Comput., 16 (1995), pp. 470--495]. From one point of view, this method can be regarded as a preconditioning technique for the interface Schur-complement operator obtained from a decomposition into nonoverlapping subdomains. From another point of view, it can be viewed as a method of the Schwarz type for overlapping subdomains, but with an "overlap" between the physical space in one subdomain and the leading components of the eigenspace induced by the Steklov--Poincaré operator in the complementary domain.
Remark on Algorithm 716
Authors: F. J. Testa, Robert J. Renka
Venue: ACM Transactions on Mathematical Software (TOMS) (1999)

The curve-fitting package TSPACK has been converted to double precision. Also, portability has been improved by eliminating some potential errors.
The user's mental model of an information retrieval system
Authors: Christine L. Borgman
Venue: Proceedings of the 8th annual international ACM SIGIR conference on Research and development in information retrieval (1985)

An empirical study was performed to train naive subjects in the use of a prototype Boolean logic-based information retrieval system on a bibliographic database. Subjects were undergraduates with little or no prior computing experience. Subjects trained with a conceptual model of the system performed better than subjects trained with procedural instructions, but only on complex, problem-solving tasks. Performance was equal on simple tasks. Differences in patterns of interaction with the system (based on a stochastic process model) showed parallel results. Most subjects were able to articulate some description of the system's operation, but few articulated a model similar to the card catalog analogy provided in training. Eleven of 43 subjects were unable to achieve minimal competency in system use. The failure rate was equal between training conditions and genders; the only differences found between those passing and failing the benchmark test were academic major and in frequency of library use.
Computing rank-revealing QR factorizations of dense matrices
Authors: Christian H. Bischof, G. Quintana-Ortí
Venue: ACM Transactions on Mathematical Software (TOMS) (1998)

We develop algorithms and implementations for computing rank-revealing QR (RRQR) factorizations of dense matrices. First, we develop an efficient block algorithm for approximating an RRQR factorization, employing a windowed version of the commonly used Golub pivoting strategy, aided by incremental condition estimation. Second, we develop efficiently implementable variants of guaranteed reliable RRQR algorithms for triangular matrices originally suggested by Chandrasekaran and Ipsen and by Pan and Tang. We suggest algorithmic improvements with respect to condition estimation, termination criteria, and Givens updating. By combining the block algorithm with one of the triangular postprocessing steps, we arrive at an efficient and reliable algorithm for computing an RRQR factorization of a dense matrix. Experimental results on IBM RS/6000 SGI R8000 platforms show that this approach performs up to three times faster that the less reliable QR factorization with column pivoting as it is currently implemented in LAPACK, and comes within 15% of the performance of the LAPACK block algorithm for computing a QR factorization without any column exchanges. Thus, we expect this routine to be useful in may circumstances where numerical rank deficiency cannot be ruled out, but currently has been ignored because of the computational cost of dealing with it.