Dan I. Moldovan

On the design of algorithms for VLSI systolic arrays

This paper is concerned with the mapping of cyclic loop algorithms into special-purpose VLSI arrays. The mapping procedure is based on the mathematical transformations of index sets and data dependence vectors. Necessary and sufficient conditions for the existence of valid transformations are given for algorithms with constant data dependences. Two examples of different algorithms are given to illustrate the proposed mapping procedure; first is the LU decomposition of a matrix which leads to constant data dependence vectors, and secondly is the dynamic programming which leads to dependences which are functions on the index set and are more difficult to be mapped into VLSI arrays.

On the Analysis and Synthesis of VLSI Algorithms

This correspondence is concerned with the development of algorithms for special-purpose VLSI arrays. The approach used in this correspondence is to identify algorithm transformations which modify favorably the index set and the data dependences, but perserve the ordering imposed on the index set by the data dependences. Conditions for the existance of such transformations are given for a class of algorithms. Also, a methodology is proposed for the synthesis of VLSI algorithms.

Acquisition of linguistic patterns for knowledge-based information extraction

The paper presents an automatic acquisition of linguistic patterns that can be used for knowledge based information extraction from texts. In knowledge based information extraction, linguistic patterns play a central role in the recognition and classification of input texts. Although the knowledge based approach has been proved effective for information extraction on limited domains, there are difficulties in construction of a large number of domain specific linguistic patterns. Manual creation of patterns is time consuming and error prone, even for a small application domain. To solve the scalability and the portability problem, an automatic acquisition of patterns must be provided. We present the PALKA (Parallel Automatic Linguistic Knowledge Acquisition) system that acquires linguistic patterns from a set of domain specific training texts and their desired outputs. A specialized representation of patterns called FP structures has been defined. Patterns are constructed in the form of FP structures from training texts, and the acquired patterns are tuned further through the generalization of semantic constraints. Inductive learning mechanism is applied in the generalization step. The PALKA system has been used to generate patterns for our information extraction system developed for the fourth Message Understanding Conference (MUC-4). >

ADVIS: A Software Package for the Design of Systolic Arrays

A methodology for mapping numerical algorithms into systolic arrays is presented in this paper. This mapping is done using a transformation function which transforms the original sequential algorithm into a suitable parallel form. A program was developed to automatically generate this transformation. We consider both the case of arbitrarily large systolic arrays as well as the more realistic case of fixed-size systolic arrays requiring algorithm partitioning. An example of the algorithm is given to present the methodology and the results obtained with the program.

Parallelism detection and transformation techniques useful for VLSI algorithms

Abstract An algorithm model is introduced in which the time/space characteristics of an algorithm are implicitly represented by a set of data dependencies. The concepts of execution ordering, syntactical algorithm equivalence, algorithm transformation, and dependent computations are defined in terms of the model. Sufficient conditions for the existence of large sets of independent computations are derived. The concepts of linear and relaxed orderings are introduced to allow the description of “fast” execution orderings. Sufficient conditions for the use of linear and relaxed orderings as execution orderings for a given algorithm are also given. On the basis of these conditions, time transformations are defined and it is shown how they can be selected so that equivalent transformed algorithms have short execution times. A model for VLSI array (computation) is introduced and it is shown how to select a space transformation for mapping an algorithm into a new (VLSI) algorithm.

Acquisition of semantic patterns for information extraction from corpora

A knowledge acquisition tool to extract semantic patterns for a memory-based information retrieval system is presented. The major goal of this tool is to facilitate the construction of a large knowledge base of semantic patterns. The system acquires semantic patterns from texts with a small amount of user interaction. It acquires new phrasal patterns from the input text, maps each element of the pattern to a meaning frame, generalizes the acquired pattern, and merges it into the current knowledge base. Interaction with the user is introduced at some decision points, where the ambiguity cannot be resolved automatically without other pieces of predefined knowledge. The acquisition process is described in detail, and a preliminary experimental result is discussed.<<ETX>>

Data broadcasting in linearly scheduled array processors

A major problem in executing algorithms in array processors is the implementation of broadcasts without unnecessary speed-up factor degradation. We discuss when and how broadcasts can be eliminated or reduced to easily implementable sequences of reduced local broadcasts. Algorithms are modelled as a structured set of indexed computations which operate on variables associated with a referencing or indexing function. The discussion is restricted to variables with linear indexing functions and to algorithms linearly scheduled for execution in array processors. Linear indexing functions are represented as affine matricial functions of the index set of the algorithm. The linear part of such representation is a coefficient matrix denoted the indexing matrix. Linear schedules are defined as linear time-space allocation functions mapping the computations of an algorithm into time and processors. We discuss necessary and sufficient conditions for the occurrence of broadcasts in a linearly scheduled algorithm. Necessary and sufficient conditions and constructive criteria are given for selecting linear schedules for which all broadcasts are eliminated or reduced to sequences of small local broadcasts.

The state of the art in parallel production systems

Abstract The production system paradigm occupies a prominent place in artificial intelligence. Production systems have not yet been widely accepted in industry mainly due to their slow performance. Continuing research in knowledge processing requires larger and larger production systems, which would only exacerbate the performance problem. For this reason, it is important to apply parallel processing technology to production systems because it may provide the speed improvement necessary for future production systems. This paper examines recent research efforts in production systems. It begins by discussing the architecture of production systems and the cause of their slow performance. It groups the research efforts into three categories, faster sequential match algorithms, parallel match production systems, and multiple rule firing production systems, and analyzes the strength and weakness of each approach. A uniform terminology is used throughout the paper. By considering each category individually and comparing them collectively, a clear picture of recent research efforts in production systems is obtained.

RUBIC: a multiprocessor for rule-based systems

It is shown how sequential production systems can be transformed into equivalent parallel forms by performing an analysis of rule interdependence. In the parallel production system model, rules fire simultaneously and the search space is reduced from the original form. A multiprocessor called RUBIC (rule-based inference computer) was designed to implement the parallel processing model. RUBIC has a message-passing architecture. The partitioning and mapping of production systems into the multiprocessor is achieved by optimizing a performance index such that inherent parallelism is maximized and interprocessor communication is minimized. >

Report on workshop on high performance computing and communications for grand challenge applications: computer vision, speech and natural language processing, and artificial intelligence

The findings of a workshop, the goals of which were to identify applications, research problems, and designs of high performance computing and communications (HPCC) systems for supporting applications are discussed. In computer vision, the main scientific issues are machine learning, surface reconstruction, inverse optics and integration, model acquisition, and perception and action. In speech and natural language processing (SNLP), issues were identified statistical analysis in corpus-based speech and language understanding, search strategies for language analysis, auditory and vocal-tract modeling, integration of multiple levels of speech and language analyses, and connectionist systems. In AI, important issues that need immediate attention include the development of efficient machine learning and heuristic search methods that can adapt to different architectural configurations, and the design and construction of scalable and verifiable knowledge bases, active memories, and artificial neural networks. >