Jeffrey R. Carter

Practical use of Ada 95's concurrency features

Ada 83 has numerous shortcomings for concurrent systems: it requires additional tasks, adding overhead and increasing interrupt latency, and it has difficulty handling asynchronous transfer of control. Ada 95 offers features that address these shortcomings and simplify concurrent implementation: protected units, interrupt handlers, priority entry queuing, dynamic task priorities, and asynchronous select statements. Using their Flexible Manufacturing System, the authors demonstrate how these features improve Ada and promote efficiency.

Removing and adding network connections with recursive-error-minimization equations

One of the key features of Recursive Error Minimization (REM) equations is the efficient computation of the second derivative of mean square error with respect to each connection. The approximate integration of this derivative provides an estimate of the effect of removing or adding connections. A network with a minimum number of connections can then be found for a specific learning task. This has two important consequences. First the explanation of network decisions is much simpler with a minimum net. Second the computational load is a function of the number of connections. Results are presented for learning the English alphabet and for a simpler task learning the first seven letters of the alphabet. 1.

Generalizing from a small set of training exemplars for handwritten digit recognition

The ability of a neural network to generalize from a small set of handwritten digit training exemplars is dramatically improved with two new techniques. First, the number of neural network inputs is drastically reduced by using a log-polar coordinate system to produce a centered, constant size, constant average brightness image of 65 pixels which still retains sufficient information for discrimination. Second, generalized training examples are constructed from the training exemplars with carefully chosen random variations. The results of this work are impressive. The prior state of the art, Le Cun et al., used binary images, 784 inputs, 4635 nodes, 98442 connections, 9840 training exemplars, and required three days to train on a Sun SPARCstation 1. This work used 65 inputs, 75 nodes, 660 connections, 160 training exemplars, and required one hour to train on an AT-class PC, yet its results appear to be similar to those reported by Le Cun et al.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The form of reusable Ada components for concurrent use

Abstract data types are often chosen to implement reusable Ada components for sequential use. Those who have attempted to expand from sequential to concurrent considerations have frequently continued to use abstract data types for their implementation. This approach is shown to violate software engineering principles. The use of abstract state machines for concurrent components is shown to resolve these problems.

MMAIM: a software development method for Ada

Traditional methods for software development fail to make use of Adas unique features to support software engineering principles. Several methods have been proposed to overcome this problem, but shortcomings have been identified with all of them. A method for Ada software development is presented which avoids the shortcomings of existing methods. Further work required on the method is also discussed.

Ada's design goals and object-oriented programming

Ada was designed to support and enforce software-engineering principles to promote the development of programs which are easy to read and understand. Ada 9X, the proposed revision to Ada 83, includes features for object-oriented programming, including inheritance and dispatching. Object-oriented programming is shown to emphasize ease of writing over readability and under-standability, violating one of Adas main design goals. A significant example demonstrates that object-oriented programming reduces readability and understandability.

Ada 9X reusable components

The inclusion of concurrency in Ada leads to multiple reusable components which implement th e same abstraction. The proposed modifications of Ada 9X contain features which may eliminate th e need for more than one version of an abstraction. An example of an Ada 9X component illustrates the use of these features.

Concurrent reusable abstract data types

A commonly used form of concurrent abstract data types always leads to erroneous execution. A corrected version of this form, suggested in the article which pointed out this problem, is not considered to be acceptable software engineering practice by the author. An acceptable correct form is presented.

Mobile Robot Navigation With Ambiguous Sparse Landmarks

A robust, non-linear filter with parametric memory is applied to the case of a mobile robot with inaccurate dead reckoning. The robot occasionally receives ambiguous information from known landmarks. The ability of the filter to fuse data in space and time is demonstrated and parametric navigation performance is presented.

MMAIM: a software development method for Ada, part II—Example

Part I of this paper described the notation and method for the Martin Marietta Ada Implementation Method (MMAIM). Part II demonstrates the use of MMAIM with an example. This allows the quality of the solution produced by MMAIM to be evaluated.