Using Message Passing Instead of the GOTO Construct

This report describes research conducted at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for this research was provided in part by the Office of Naval Research of the Department of Defense under Contract N00014-75-C-0522.This paper advocates a programming methodology using message passing. Efficient programs are derived for fast exponentiation, merging ordered sequences, and path existence determination in a directed graph. The problems have been proposed by John Reynolds as interesting ones to investigate because they illustrate significant issues in programming. The methodology advocated here is directed toward the production of programs that are intended to execute efficiently in a computing environment with many processors. The absence of the GOTO construct does not seem to be constricting in any respect in the development of efficient programs using the programming methodology advocated here.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

Transforming EVENT B Models into Verified C# Implementations

The refinement-based approach to developing software is based on the correct-by-construction paradigm where software systems are constructed via the step-by-step refinement of an initial high-level specification into a final concrete specification. Proof obligations, generated during this process are discharged to ensure the consistency between refinement levels and hence the system’s overall correctness. Here, we are concerned with the refinement of specifications using the EVENT B modelling language and its associated toolset, the RODIN platform. In particular, we focus on the final steps of the process where the final concrete specification is transformed into an executable algorithm. The transformations involved are (a) the transformation from an EVENT B specification into a concrete recursive algorithm and (b) the transformation from the recursive algorithm into its equivalent iterative version. We prove both transformations correct and verify the correctness of the final code in a static program verification environment for C# programs, namely the Spec# programming syste

Evolving Parallel Programs

This report describes research conducted at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for this research was provided in part by the Office of Naval Research of the Department of Defense under Contract N00014-75-C-0522.Message passing is directed toward the production of programs that are intended to execute efficiently in a computing environment with a large number of processors. The paradigm attempts to address the computational issues of state change and communication directly with appropriate primitives. Efficient programs are evolved for fast factorial and path existence determination in a directed graph. This paper is a contribution to the continuing debate on programming methodology. It advocates that simple initial implementations of programs should be constructed and then the implementations should be evolved to meet their partial specifications where it is anticipated that the partial specifications will themselves evolve with time. The programming methodology used in this paper is intended for use with an actor machine which consists of a large number of processors connected by a high bandwidth network. We evolve implementations for factorial and for the path existence problem that execute in the logarithm of the amount of time required on a conventional machine. The implementation (with no redundant exploration) of the path existence problem evolved in this paper is more efficient than any implementation that can be programmed in a dialect of pure LISP that allows the arguments to a function to be evaluated in parallel. This is evidence that applicative programming in languages like pure LISP is apparently less efficient in some practical applications. The efficiency of such applicative languages is important because many computer scientists are proposing to use them on future generation parallel machines whose architectures exploit ultra large scale integration.MIT Artificial Intelligence Laboratory Department of Defense Advanced Research Projects Agenc

Slivers, computational modularity via synchronized lazy aggregates

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (p. 435-442).by Farnklyn Albin Turbak.Ph.D