195862034
Error bounded Pade approximation via bilinear conformal transformation
Since asymptotic waveform evaluation (AWE) was introduced, many interconnect model order reduction methods via Pade approximation have been proposed. Although the stability and precision of model reduction methods have been greatly improved, the following important question has not been answered: "What is the error bound in the time domain?". This problem is mainly caused by the "gap" between the frequency domain and the time domain, i.e., a good approximated transfer function in the frequency domain may not be a good approximation in the time domain. All of the existing methods approximate the transfer function directly in the frequency domain and hence can not provide error bounds in the time domain. In this paper, we present new moment matching methods which can provide guaranteed error bounds in the time domain. Our methods are based on the classic work by Teasdale (1953) which performs Pade approximation in a transformed domain by the bilinear conformal transformation s=(1-z)/(1+z).
7360354
Fast performance-driven optimization for buffered clock trees based on Lagrangian relaxation
Delay, power, skew, area, and sensitivity are the most important concerns in current clock-tree design. We present in this paper an algorithm for simultaneously optimizing the above objectives by sizing wires and buffers in clock trees. Our algorithm, based on Lagrangian relaxation method, can optimally minimize delay, power, and area simultaneously with very low skew and sensitivity. With linear storage overall and linear runtime per iteration, our algorithm is extremely economical, fast, and accurate; for example, our algorithm can solve a 6201-wire-segment clock-free problem using about 1-minute runtime and 1.3-MB memory and still achieve pico-second precision on an IBM RS/6000 workstation.
61819982
Optimal non-uniform wire-sizing under the Elmore delay model
We consider non-uniform wire-sizing for general routing trees under the Elmore delay model. Three minimization objectives are studied: (1) total weighted sink-delays; (2) total area subject to sink-delay bounds; and (3) maximum sink delay. We first present an algorithm NWSA-wd for minimizing total weighted sink-delays based on iteratively applying the wire-sizing formula in [1]. We show that NWSA-wd always converges to an optimal wire-sizing solution. Based on NWSA-wd and the Lagrangian relaxation technique, we obtained two algorithms NWSA-db and NWSA-md which can optimally solve the other two minimization objectives. Experimental results show that our algorithms are efficient both in terms of runtime and storage. For example, NWSA-wd, with linear runtime and storage, can solve a 6201-wire segment routing-tree problem using about 1.5-second runtime and 1.3-MB memory on an IBM RS/6000 workstation.
12098402
Noise-aware repeater insertion and wire-sizing for on-chip interconnect using hierarchical moment-matching
Recently, several algorithms for interconnect optimization via repeater insertion and wire sizing have appeared based on the Elmore delay model. Using the Devgan noise metric a noise-aware repeater insertion technique has also been proposed recently. Recognizing the conservatism of these delay and noise models, we propose a moment-matching based technique to interconnect optimization that allows for much higher accuracy while preserving the hierarchical nature of Elmore-delay-based techniques. We also present a novel approach to noise computation that accurately captures the effect of several attackers in linear time with respect to the number of attackers and wire segments. Our practical experiments with industrial nets indicate that the corresponding reduction in error afforded by these more accurate models justifies this increase in runtime for aggressive designs which is our targeted domain. Our algorithm yields delay and noise estimates within 5% of circuit simulation results.
21349955
A unified optimization framework for microelectronics industry
In this paper, an object-oriented unified optimization framework (UOF) for general problem optimization is proposed. Based on evolutionary algorithms, numerical deterministic methods, and C++ objective design, the UOF possesses real-world applications for various optimization problems. The UOF is with interface between defining a general problem and generic solver; hence the two areas are bridged. The UOF's components are categorized into problem and solver parts, and they work independently. Therefore, the reusable high level code allows the adaptation to new problem and solver quickly. Practical applications in microelectronics industry confirm the functionality of the developed unified optimization framework.
26496434
Visual interfaces to digital libraries
Today's digital libraries (DLs) are content rich, multimedia, multilingual collections that are distributed and accessed worldwide. Designing useful interfaces to access, understand, and manage this knowledge has become an active and challenging field of study. Visual interfaces to DLs aim to shift the user's mental load from slow reading to faster perceptual processes such as visual pattern recognition. They draw on progress in the new field of Information Visualization.The workshop in 2002 continues the theme started at JCDL 2001. In addition, the growth of the field warrants new perspectives on some of the issues we have addressed last year.
260704
An implementation of parallel dynamic load balancing for adaptive computing in VLSI device simulation
A new parallel semiconductor device simulation using the dynamic load balancing approach is presented. This semiconductor device simulation based on adaptive finite volume error estimation, and monotone iterative methods has been developed and implemented on a Linux-cluster with MPI library. Two different parallel versions of the algorithm to perform a complete device simulation are proposed. The first one is a dynamic parallel domain decomposition approach. The second version is a parallel current-voltage characteristic points simulation. The implementation shows that a well-designed load balancing simulation can reduce the execution time up to an order of magnitude. Compared with the measured data, numerical simulations on P-N diode, N-MOSFET, and DTMOS devices are presented to show the accuracy and efficiency of the method.
42451139
Visualizing scientific paradigms: An introduction
This special topic issue includes a collection of seven articles on visualizing scientific paradigms. All articles in this special issue reflect the influence of Thomas Kuhn’s structure of scientific revolutions on our understanding of the growth of scientific knowledge. On the other hand, each article represents a unique perspective of how one may pursue the quest for transforming something as intangible and empirically evasive as invisible colleges and competing paradigms into something that is more accessible and traceable to scholars and professions of various disciplines, ranging from historians, philosophers, and educators to scientists and engineers. The opening article is Henry Small’s personal account of the endeavor in probing scientific paradigms using science mapping. His article, entitled “Paradigms, Citations and Maps of Science: A Personal History,” provides a valuable introduction to the key issues involved in this area and reveals an overview of promising avenues as well as challenging routes. He identifies an emerging trend that reflects and redefines Kuhn’s paradigms and emphasizes the empirical viability of research methodologies in understanding the growth of scientific knowledge. He suggests that revolutionary and normal science should be seen as extremes on a continuum of rates of change rather than, as Kuhn originally asserted, as an all-or-none proposition. The second and third articles take a prominent historical perspective in depicting the evolution of scientific citations. Eugene Garfield and his collaborators’ article is entitled “Why Do We Need Algorithmic Historiography?” They explain the rationale for creating HistCite, their new program that produces historiographs of scholarly topics. These historiographs help analysts and historians identify key events, people, and journals in a particular field. Scholars can evaluate the evolution of a scientific paradigm by studying the genealogic profile of such evolution. The third article is entitled “Timeline Visualization of Research Fronts.” Steven Morris and his colleagues focus on temporal changes in research fronts and explain the power of timeline visualizations. They first cluster documents into research fronts based on bibliographic coupling and then visualize research fronts using horizontal timeline tracks. Documents from research fronts are plotted along corresponding timeline tracks. Because time line visualizations can reveal temporal relations among research fronts and their member documents, time lines are potentially useful tools in identifying new research fronts as well as existing research expertise and research excellence. Although both the fourth and fifth articles have connections to Pathfinder networks, they address different topics. Howard White’s article, entitled “Pathfinder Networks and Author Cocitation Analysis: A Remapping of Paradigmatic Information Scientists,” clarifies an important methodological issue, whereas Chen and Kuljis focus on a general framework for visualizing scientific paradigms in their article. Author Cocitation Analysis (ACA) is a long established methodology for studying intellectual structures. Researchers have routinely used Pearson correlation coefficients rather than raw cocitation counts as the measure of similarity between author pairs. Howard White compellingly demonstrates the advantages of using raw cocitation counts in Pathfinder network visualizations of author cocitation structures. He compares Pathfinder networks of the information scientists derived from raw cocitation counts and Pearson correlation coefficients, respectively. In the fifth article “The Rising Landscape: A Visual Exploration of Superstring Revolutions in Physics,” Chen and Kuljis introduce a general framework for visualizing the growth of scientific paradigms based on Kuhn’s theory on scientific revolutions. They illustrate the use of this framework in a case study of superstring revolutions in physics. The evolution of cocitation networks is depicted and explained through animated visualizations of citations and cocitation links. Visual-spatial properties as well as structural patterns associated with superstring revolutions are identified. The sixth and seventh articles deal with heterogeneous data sources. In their article entitled “Indicator-Assisted Evaluation and Funding of Research: Visualizing the Influ© 2003 Wiley Periodicals, Inc.
11939689
Delineating the citation impact of scientific discoveries
Identifying the significance of specific concepts in the diffusion of scientific knowledge is a challenging issue concerning many theoretical and practical areas. We introduce an innovative visual analytic approach to integrate microscopic and macroscopic perspectives of a rapidly growing scientific knowledge domain. Specifically, our approach focuses on statistically unexpected phrases extracted from unstructured text of titles and abstracts at the microscopic level in association with the magnitude and timeliness of their citation impact at the macroscopic level. The H-index, originally defined to measure individual scientists. productivity in terms of their citation profiles, is extended in two ways: 1) to papers and terms as a means of dividing these items into two groups so as to replace the less optimal threshold-based divisions, and 2) to take into account the timeliness of the impact of knowledge diffusion in terms of the timing of citations and publications so that attention is particularly drawn towards potentially significant and timely papers. The selected terms are connected to higher-level performance indicators, such as measures derived from the H-index, in the form of decision trees. A top-down traversal of such decision trees provides an intuitive walkthrough of concepts and phrases that may underline potentially significant but currently still latent scientific discoveries. Timeliness measures can also help to identify institutions that are at the forefront of a research field. We illustrate how widely accessible tools such as Google Earth can be utilized to disseminate such insights. The practical significance for digital libraries and fostering scientific discoveries is demonstrated through the astronomical literature related to the Sloan Digital Sky Survey (SDSS).