15818010
Automatic Partitioner for Behavior Level Distributed Logic Simulation
As the complexity of circuit design increases, verification through simulation has become a bottleneck of the IC design process. Distributed parallel simulation is one way to solving the problem. In order to distribute the simulation workload to multiple processors, the design must be carefully partitioned first. While most previous work focus on gate level partitioning, our work extends a previously implemented Verilog gate-level partitioner to support RTL and behavior level partitioning. Techniques to partition special constructs specific to these levels, such as global access, function calls and memory access, are described in this paper. The experimental results show that our techniques are capable of finding partitions which can accelerate simulation.
14390424
A Temporal Assertion Extension to Verilog
Many circuit designs need to follow some temporal rules. However, it is hard to express and verify them in the past. Therefore, a temporal assertion extension to Verilog, called Temporal Wizard, is proposed in this paper. It provides several Verilog system tasks for the users to write assertions in testbench directly. Two new concepts, tag and thread, are also introduced so that data can be associated with temporal assertions and provide more functionalities than previous temporal assertion checkers.
61942372
Simulation-based bug trace minimization with BMC-based refinement
Finding the cause of a bug can be one of the most time-consuming activities in design verification. This is particularly true in the case of bugs discovered in the context of a random simulation- based methodology, where bug traces, or counter-examples, may contain several hundred thousand cycles. In this work we propose Butramin, a bug trace minimizer. Butramin considers a bug trace produced by a random simulator or a semi-formal verification software and produces an equivalent trace of shorter length. Butramin applies a range of minimization techniques, deploying both simulation-based and formal methods, with the objective of producing highly reduced traces that still expose the original bug. We evaluated Butramin on a range of designs, including the publicly available picoJava microprocessor. Our experiments show that in most cases Butramin is able to reduce traces to a small fraction of their initial size, in terms of cycle length and signals involved.
5912642
Predicate rewriting for translating Boolean queries in a heterogeneous information system
Searching over heterogeneous information sources is difficult in part because of the nonuniform query languages. Our approach is to allow users to compose Boolean queries in one rich front-end language. For each user query and target source, we transform the user query into a subsuming query that can be supported by the source but that may return extra documents. The results are then processed by a filter query to yield the correct final results. In this article we introduce the architecture and associated mechanism for query translation. In particular, we discuss techniques for rewriting predicates in Boolean queries into native subsuming forms, which is a basis of translating complex queries. In addition, we present experimental results for evaluating the cost of postfiltering. We also discuss the drawbacks of this approach and cases when it may not be effective. We have implemented prototype versions of these mechanisms and demonstrated them on heterogeneous Boolean systems.
206782514
Top-k Query Processing in Uncertain Databases
Top-k processing in uncertain databases is semantically and computationally different from traditional top-k processing. The interplay between score and uncertainty makes traditional techniques inapplicable. We introduce new probabilistic formulations for top-k queries. Our formulations are based on "marriage" of traditional top-k semantics and possible worlds semantics. In the light of these formulations, we construct a framework that encapsulates a state space model and efficient query processing techniques to tackle the challenges of uncertain data settings. We prove that our techniques are optimal in terms of the number of accessed tuples and materialized search states. Our experiments show the efficiency of our techniques under different data distributions with orders of magnitude improvement over naive materialization of possible worlds.
5758816
Boolean Query Mapping Across Heterogeneous Information Sources
Searching over heterogeneous information sources is difficult because of the nonuniform query languages. Our approach is to allow a user to compose Boolean queries in one rich front end language. For each user query and target source, we transform the user query into a subsuming query that can be supported by the source but that may return extra documents. The results are then processed by a filter query to yield the correct final result. We introduce the architecture and associated algorithms for generating the supported subsuming queries and filters. We show that generated subsuming queries return a minimal number of documents; we also discuss how minimal cost filters can be obtained. We have implemented prototype versions of these algorithms and demonstrated them on heterogeneous Boolean systems.
4362821
PEBL: positive example based learning for Web page classification using SVM
Web page classification is one of the essential techniques for Web mining. Specifically, classifying Web pages of a user-interesting class is the first step of mining interesting information from the Web. However, constructing a classifier for an interesting class requires laborious pre-processing such as collecting positive and negative training examples. For instance, in order to construct a "homepage" classifier, one needs to collect a sample of homepages (positive examples) and a sample of non-homepages (negative examples). In particular, collecting negative training examples requires arduous work and special caution to avoid biasing them. We introduce in this paper the Positive Example Based Learning (PEBL) framework for Web page classification which eliminates the need for manually collecting negative training examples in pre-processing. We present an algorithm called Mapping-Convergence (M-C) that achieves classification accuracy (with positive and unlabeled data) as high as that of traditional SVM (with positive and negative data). Our experiments show that when the M-C algorithm uses the same amount of positive examples as that of traditional SVM, the M-C algorithm performs as well as traditional SVM.
32378250
Using Distributed Objects to Build the Stanford Digital Library Infobus
For digital libraries to thrive, the providers of information processing services must be able to evolve their systems autonomously. However, as the complexity of their offerings increases, software tools more sophisticated than existing Web facilities are needed. Distributed object technology may be the answer. The availability of high-volume, increasingly sophisticated information is making the need for metadata facilities more urgent. Traditional, library-based approaches break down when used in an advanced digital library. More modular mechanisms are needed, and the CORBA system is one approach. Digital libraries are affected at a deep technical level by the widely differing user traditions of Web users and library patrons. The challenge and opportunity of digital libraries will be the synthesis of these traditions. The authors set out to create a technical infrastructure to support the construction of digital libraries. In their view, a digital library comprises widely distributed resources that can be maintained autonomously by different organizations and will not require adherence to uniform interfaces.