16104056
Performance analysis and design of a logic simulation machine
The high costs associated with logic simulation of large VLSI circuits has led to the need for new computer architectures tailored to the simulation task. Such architectures have the potential for significant speed-ups over software-based logic simulators executing on standard sequential computers. This paper presents a model of one class of multiprocessor simulation architectures and compares the performance of some of these machines using data obtained from simulations of VLSI circuits. In addition, we discuss the implications of our results on machine design and examine the sensitivity of the model to variations in circuit characteristics.
11030217
The open network laboratory
The Open Network Laboratory (ONL) is a remotely accessible network testbed of high performance routers which has been designed with an eye towards ease of use for users from the naïve to the expert. The system is built around a set of high-performance routers that are extendible and easily configurable through the Remote Laboratory Interface (RLI), an intuitive graphical interface. The RLI also makes it easy to configure packet filters in the routers, assign flows or flow aggregates to separate queues with configurable QoS and attach hardware monitoring points to real-time charts. The RLI's real-time charts and user data facility make it easy to directly view the effects of traffic as it moves through a router, allowing the user to gain better insight into system behavior and create compelling demonstrations. Each port of the router is equipped with an embedded processor that supports software plugins which allow users to extend the system's functionality. This paper describes the ONL and how it can be used in networking education. Our web site onl.arl.wustl.edu includes a short video and a tutorial.
15226793
Code migration through transformations: an experience report
One approach to dealing with spiraling maintenance costs, manpower shortages and frequent breakdowns for legacy code is to "migrate" the code into a new platform and/or programming language. The objective of this paper is to explore the feasibility of semi-automating such a migration process in the presence of performance and other constraints for the migrant code. In particular, the paper reports on an experiment involving a medium-size software system written in PL/IX. Several modules of the system were migrated to C++, first by hand and then through a semiautomatic tool. After discovering that the migrant code was performing up to 50% slower than the original, a second migration effort was conducted which improved the performance of the migrant code substantially. The paper reports on the transformation techniques used by the transformation process and the effectiveness of the prototype tools that were developed. In addition, the paper presents preliminary results on the evaluation of the experiment.
17291567
Understanding software systems using reverse engineering technology perspectives from the Rigi project
Software engineering research has focused mainly on software construction and has neglected software maintenance and evolution. Proposed is a shift in research from synthesis to analysis. Reverse engineering is introduced as a possible solution to program understanding and software analysis. Presented is reverse engineering technology developed as part of the Rigi project. The Rigi approach involves the identification of software artifacts in the subject system and the aggregation of these artifacts to form more abstract architectural models. Reported are some analyses on the source code of SQL/DS, performed by the authors while visiting the Program Understanding project at the IBM Centre for Advanced Studies in Toronto.
33091738
SHAPES: A Novel Approach for Learning Search Heuristics in Under-Constrained Optimization Problems
Although much research in machine learning has been carried out on acquiring knowledge for problem-solving in many problem domains, little effort has been focused on learning search-control knowledge for solving optimization problems. This paper reports on the development of SHAPES, a system that learns heuristic search guidance for solving optimization problems in intractable, under-constrained domains based on the Explanation-Based Learning (EBL) framework. The system embodies two new and novel approaches to machine learning. First, it makes use of explanations of varying levels of approximation as a mean for verifying heuristic-based decisions, allowing heuristic estimates to be revised and corrected during problem-solving. The provision of such a revision mechanism is particularly important when working in intractable and under-constrained domains, where heuristics tend to be highly over-generalized, and hence at times will give rise to incorrect results. Second, it employs a new linear and quadratic programming-based weight-assignment algorithm formulated to direct search toward optimal solutions under best-first search. The algorithm offers a direct method for assigning rule strengths and, in so doing, avoids the need to address the credit-assignment problem faced by other iterative weight-adjustment methods.
37472111
Extending the superimposed codeword indexing scheme to handle incomplete information
In order to use Prolog as a basis for database applications, techniques are required for rapid retrieval of clauses from large data sets. Various researchers have contributed to the development of indexing strategies for this purpose. One such strategy is known as superimposed codeword+mask bits (SCW+MB). One extension of Prolog which is useful in the development of deductive databases is the ability to handle incomplete information. A form of incomplete information based on sets has been introduced and used in a deductive database system. In order to provide efficient access to clauses containing incomplete information, existing strategies need to be adapted accordingly. This paper presents an extension to the SCW+MB algorithm to cover incomplete information, and describes how this can be realized in hardware.
34037807
EDS: A Parallel Computer System for Advanced Information Processing
The European Declarative System (EDS) is a high performance computer server designed for developing advanced information processing systems (e.g. extended database systems, knowledge based systems, ... etc.). One major application target of EDS is to serve the needs of existing and future commercial and business professionals; and the application domain ranges from simple data-intensive on-line transaction processing to complex computation-intensive decision support systems. To achieve high performance, parallelism is exploited extensively in both the hardware and the software. In this paper, an overview of the EDS architectures and the advanced commercial applications running on the EDS system are described.