16718437
Practical Formal Verification in Microprocessor Design
Practical application of formal methods requires more than advanced technology and tools; it requires an appropriate methodology. A verification methodology for data-path-dominated hardware combines model checking and theorem proving in a customizable framework. This methodology has been effective in large-scale industrial trials, including verification of an IEEE-compliant floating-point adder.
208909301
Parametric Representations of Boolean Constraints.
9909428
Formal verification of iterative algorithms in microprocessors
Contemporary microprocessors implement many iterative algorithms. For example, the front-end of a microprocessor repeatedly fetches and decodes instructions while updating internal state such as the program counter; floating-point circuits perform divide and square root computations iteratively. Iterative algorithms often have complex implementations because of performance optimizations like result speculation, re-timing and circuit redundancies. Verifying these iterative circuits against high-level specifications requires two steps: reasoning about the algorithm itself and verifying the implementation against the algorithm. In this paper we discuss the verification of four iterative circuits from Intel microprocessor designs. These verifications were performed using Forte, a custom-built verification system; we discuss the Forte features necessary for our approach. Finally, we discuss how we maintained these proofs in the face of evolving design implementations.
17231423
Lifted-FL: A Pragmatic Implementation of Combined Model Checking and Theorem Proving
Combining theorem proving and model checking offers the tantalizing possibility of efficiently reasoning about large circuits at high levels of abstraction. We have constructed a system that seamlessly integrates symbolic trajectory evaluation based model checking with theorem proving in a higher-order classical logic. The approach is made possible by using the same programming language (fl) as both the meta and object language of theorem proving. This is done by "lifting" fl, essentially deeply embedding fl in itself. The approach is a pragmatic solution that provides an efficient and extensible Verification environment. Our approach is generally applicable to any dialect of the ML programming language and any model-checking algorithm that has practical inference rules for combining results.
62688407
Extended subject access to hypertext online documentation. Parts I and II: The search-support and maintenance problems
The DFT (DOCUMENT, FIND, THESEUS) online documentation system resembles other hypertext software in managing a full‐text database with reference links (pointers) between passages (nodes). But DFT's prime role as an end‐user reference service at a computer center where text updates are frequent required extra access methods often neglected in hypertext systems. To solve the problem of rapid, high‐recall search for specific answer passages we combined syntactical interface features (substring and fuzzy matching of search terms) with a semantic expansion of the system's entry vocabulary. Extensive aliasing increased the number of descriptions under which any passage could be found. Conversion of the NBS GAMS classification scheme for mathematical software into descriptors allowed us to impose a virtual organization on our subroutine documentation that supports easy, task‐oriented retrieval without tedious path walking. To solve the problem of reliable database maintenance amid frequent passage revisions we developed software tools for flexible input of text and entry‐term changes, as well as for thorough and versatile status reporting. These, together with special features for testing and privately simulating changes and for coordinating the sequence of text and entry‐term updates for maximum efficiency, yielded a robust and practical answer‐delivery system. © 1991 John Wiley & Sons, Inc.
7974229
Efficient validity checking for processor verification
We describe an efficient validity checker for the quantifier-free logic of equality with uninterpreted functions. This logic is well suited for verifying microprocessor control circuitry since it allows the abstraction of datapath values and operations. Our validity checker uses special data structures to speed up case splitting, and powerful heuristics to reduce the number of case splits needed. In addition, we present experimental results and show that this implementation has enabled the automatic verification of an actual high-level microprocessor description.
11914137
TREC-10 Experiments at University of Maryland CLIR and Video
The University of Maryland Researchers participated in both the Arabic-English Cross Language Information Retrieval (CLIR) and Video tracks of TREC-10. In the CLIR track, our goal was to explore effective monolingual Arabic IR techniques and effective query translation from English to Arabic for cross language IR. For the monolingual part, the use of the different index terms including words, stems, roots, and character n-grams were explored. For the English-Arabic CLIR, the use of MT, wordlist based translation, and non-dictionary words transliteration was explored. In the video track, we participated in the shot boundary detection, and known item search with the primary goals being to evaluate existing technology for shot detection and a new approach to extending simple visual image queries to video sequences. We present a general overview of the approaches, summarize the results in discuss how the algorithms are being extended.
10387396
N Semantic Classes are Harder than Two
We show that we can automatically classify semantically related phrases into 10 classes. Classification robustness is improved by training with multiple sources of evidence, including within-document cooccurrence, HTML markup, syntactic relationships in sentences, substitutability in query logs, and string similarity. Our work provides a benchmark for automatic n-way classification into WordNet's semantic classes, both on a TREC news corpus and on a corpus of substitutable search query phrases.
14017645
Cyclic Weighted Reference Counting without Delay
Weighted Reference Counting is a low communication distributed storage reclamation scheme for loosely-couple multiprocessors. The algorithm we present herein extends weighted reference counting to allow the collection of cyclic data structures. To do so, the algorithm identifies candidate objects that may be part of cycles and performs a tricolour mark-scan on their subgraph in a lazy manner to discover whether the subgraph is still in use. The algorithm is concurrent in the sense that multiple useful computation processes and garbage collection processes can be performed simultaneously.
17471934
Designing a trace format for heap allocation events
Dynamic storage allocation continues to play an important role in the performance and correctness of systems ranging from user productivity software to high-performance servers. While algorithms for dynamic storage allocation have been studied for decades, much of the literature is based on measuring the performance of benchmark programs unrepresentative of many important allocation-intensive workloads. Furthermore, to date no standard has emerged or been proposed for publishing and exchanging representative allocation workloads. In this paper, we describe a preliminary design of a trace format for such workloads and investigate its effectiveness at representing large allocation traces. Our proposal allows for a flexible encoding of information in the trace to achieve greater compression. We evaluate our preliminary design in two dimensions. First, we measure how effective these encodings are at reducing trace size. Second we consider how a meta-level specification language could be used to describe such formats and to generate trace readers and writers automatically.
6044805
GCspy: an adaptable heap visualisation framework
GCspy is an architectural framework for the collection, transmission, storage and replay of memory management behaviour. It makes new contributions to the understanding of the dynamic memory behaviour of programming languages (and especially object-oriented languages that make heavy demands on the performance of memory managers). GCspy's architecture allows easy incorporation into any memory management system: it is not limited to garbage-collected languages. It requires only small changes to the system in which it is incorporated but provides a simple to use yet powerful data-gathering API. GCspy scales to allow very large heaps to be visualised effectively and efficiently. It allows already-running, local or remote systems to be visualised and those systems to run at full speed outside the points at which data is gathered. GCspy's visualisation tool presents this information in a number of novel ways.Deep understanding of program behaviour is essential to the design of the next generation of garbage collectors and explicit allocators. Until now, no satisfactory tools have been available to assist the implementer in gaining an understanding of heap behaviour. GCspy has been demonstrated to be a practical solution to this dilemma. It has been used to analyse production Java virtual machines running applications of realistic sizes. Its use has revealed important insights into the interaction between application program and JVM and has led to the development of better garbage collectors.