Although detractors of functional programming sometimes claim that functional programming is too difficult or counterintuitive for most programmers to understand and use, evidence to the contrary can be found by looking at the popularity of spreadsheets. The spreadsheet paradigm, a first-order subset of the functional programming paradigm, has found wide acceptance among both programmers and end users. Still, there are many limitations with most spreadsheet systems.

Recent progress in worst case timing analysis of programs has made it possible to perform accurate timing analysis of pipelined execution and instruction caching, which is necessary when a RISC processor is used as the target processor of a real-time system. However, there has not been much progress in worst case timing analysis of data caching. This is mainly due to load/store instructions that reference multiple memory locations such as those used to implement array and pointer-based references. These load/store instructions are called dynamic load/store instructions and most current analysis techniques take a very conservative approach to their timing analysis. In many cases, it is assumed that each of the references from a dynamic load/store instruction will miss in the cache and replace a cache block that would otherwise lead to a cache hit. This conservative approach results in severe overestimation of the worst case execution time (WCET). This paper proposes two techniques to minimize the WCET overestimation due to such load/store instructions. The first technique uses a global data flow analysis technique to reduce the number of load/store instructions that are misclassified as dynamic load/store instructions. The second technique utilizes data dependence analysis to minimize the adverse impact of dynamic load/store instructions. This paper also compares the WCET bounds of simple benchmark programs that are predicted with and without applying the proposed techniques. The results show that they significantly (up to 20%) improve the accuracy of WCET estimation especially for programs with a large number of references from dynamic load/store instructions. 1.

In this paper we describe how to increase the visualization and interaction in the automata theory course through the use of the tools JFLAP and Pat'e. We also describe new features in these tools that allow additional visualization and interaction. New features in JFLAP include the addition of regular expressions and exploring their conversion from and to nondeterministic finite automata (NFA), and increasing the interaction in the conversion of automata to grammars. New features in Pat'e include the display of a parse tree while parsing unrestricted grammars, and improved interaction with parsing and the transformation of grammars. 1

The introduction of educational software such as JFLAP into the course Formal Languages and Automata (FLA) has created a learning environment with automatic feedback on theoretical topics. In this paper we show how we further increase the interaction in the FLA course with the expansion of additional theoretical topics in JFLAP, and how we have added grading support into JFLAP for instructors.

An automata theory course can be taught in an interactive, hands-on manner using a computer. At Duke we have been using the software tool JFLAP to provide interaction and feedback in CPS 140, our automata theory course. JFLAP is a tool for designing and running nondeterministic versions of finite automata, pushdown automata, and Turing machines. Recently, we have enhanced JFLAP to allow one to study the proofs of several theorems that focus on conversions of languages, from one form to another, such as converting an NFA to a DFA and then to a minimum state DFA. In addition, our enhancements combined with other tools allow one to interactively study LL and LR parsing methods.

There are several algorithms for producing the canonical DFA from a given NFA. While the theoretical complexities of these algorithms are known, there has not been a systematic empirical comparison between them. In this work we propose a probabilistic framework for testing the performance of automatatheoretic algorithms. We conduct a direct experimental comparison between Hopcroft 's and Brzozowski's algorithms. We show that while Hopcroft's algorithm has better overall performance, Brzozowski's algorithm performs better for "highdensity " NFA. We also consider the universality problem, which is traditionally solved explicitly via the subset construction. We propose an encoding that allows this problem to be solved symbolically via a model-checker. We compare the performance of this approach to that of the standard explicit algorithm, and show that the explicit approach performs significantly better.

Abstract. We present the development of a theory of stored threads and their execution. The work builds upon Maurer’s theory of computer instructions and the thread algebra of Bergstra et al. The theory being developed is primarily relevant to the design of new processor architectures. We also relate Maurer’s model for computers with Turing machines, and stored threads with programs as considered in the program algebra of Bergstra et al.

Abstract. While processor based systems often enforce memory protection to prevent the unintended sharing of data between processes, current systems built around reconfigurable hardware typically offer no such protection. Several reconfigurable cores are often integrated onto a single chip where they share external resources such as memory. While this enables small form factor and low cost designs, it opens up the opportunity for modules to intercept or even interfere with the operation of one another. We investigate the design and synthesis of a memory protection mechanism capable of enforcing policies expressed as a formal language. Our approach includes a specialized compiler that translates a policy of legal sharing to reconfigurable logic blocks which can be directly transferred to an FPGA. The efficiency of our access language design flow is evaluated in terms of area and cycle time across a variety of security scenarios.

We have developed visual and interactive tools to be used by instructors to teach computer science and by students to learn concepts in a visual and hands-on manner. We describe two such tools and their use in computer science courses, JAWAA for easy creation of animations and JFLAP for experimenting with different types of automata and grammars.

This paper describes an Automatic Speech Understanding (ASU) system used in a human-robot interface for the remote control of a mobile robot. The intended application is that of an operator issuing telecontrol commands to one or more robots from a remote workstation. ASU is supposed to be performed with continuous speech, speaker independence, and quasi real time conditions. Training and testing of the system was based on speech data collected by means of Wizard of Oz simulations. Two kinds of robustness factors are introduced: the first is a recognition-errortolerant approach to semantic interpretation, the second is based on a technique for evaluating the reliability of the ASU system output with respect to the input utterance. Preliminary results are 93% correct semantic interpretations, and 96.5% correct detection of out-of-domain sentences at the cost of rejecting 6.7% correct in-domain sentences. I. Introduction This paper describes an Automatic Speech Understanding (ASU) syste...