Probabilistic diagnostics with P-graphs

This paper presents a novel approach for solving the probabilistic diagnosis problem in multiprocessor systems. The main idea of the algorithm is based on the reformulation of the diagnostic procedure as a P-graph model. The same, well-elaborated mathematical paradigm - originally used to model material flow - can be applied in our approach to model information flow. This idea is illustrated by deriving a maximum likelihood diagnostic decision procedure. The diagnostic accuracy of the solution is considered on the basis of simulation measurements, and a method of constructing a general framework for different aspects of a complex problem is demonstrated with the use of P-graph models

Gradient based system-level diagnosis

Traditional approaches in system-level diagnosis in multiprocessor systems are usually based on the oversimplified PMC test invalidation model, however Blount introduced a more general model containing conditional probabilities as parameters for different test invalidation situations. He suggested a lookup table based approach, but no algorithmic solution has been elaborated until our P-graph based solution introduced in previous publications. In this approach the diagnostic process is formulated as an optimization problem and the optimal solution is determined. Although the average behavior of the algorithm is quite good, the worst case complexity is exponential. In this paper we introduce a novel group of fast diagnostic algorithms that we named gradient based algorithms. This approach only approximates the optimal maximum likelihood or maximum a posteriori solution, but it has a polynomial complexity of the magnitude of O\left (N \cdot NbCount + N^2\right ), where N is the size of the system and NbCount is number of neighbors of a single unit. The idea of the base algorithm is that it takes an initial fault pattern and iterates till the likelihood of the actual fault pattern can be increased with a single state-change in the pattern. Improvements of this base algorithm, complexity analysis and simulation results are also presented. The main, although not exclusive application field of the algorithms is wafer-scale diagnosis, since the accuracy and the performance is still good even if relative large number of faults are present

DESIGN FOR TESTABILITY WITH HW-SW CODESIGN

Current trends in the development of design automation tools aim at a radical increase in productivity by offering highly automated design tools. As applications include even critical control applications, dependability becomes an important design issue. A novel approach supporting concurrent diagnostic engineering using a dataflow behavioural description is presented in this paper. The basic idea of this new method is the extension of the descriptions of the functional elements with the models of fault effects and fault propagation at each level of the hardware-software codesign hierarchy, thus allowing design for testability of digital computing systems. Using the presented approach test generation can be done cuncurrently with the system design and not only in the back-end design phase as it had been done previously. For test generation purposes the generalized forms of the well-known logic gate level test design algorithms call be used

Sponsors

This conference is the fifth in a series. The organizers have tried to get together those PhD students who work on any fields of computer science and its applications to help them possibly in writing their first abstract and paper, and may be to give their first scientific talk. As far as we know, this is one of the few such conferences. The aims of the scientific meeting were determined on the council meeting of the Hungarian PhD Schools in Informatics: it should • provide a forum for PhD students in computer science to discuss their ideas and research results, • give a possibility to have constructive criticism before they present the results in professional conferences, • promote the publication of their results in the form of fully refereed journal articles, and finally • promote hopefully fruitful research collaboration among the participants. The best talks will be awarded with the help of our sponsors. The papers emerging from the presented talks will be forwarded to the journals of Acta Cybernetica (Szeged), and Periodica Polytechnica (Budapest); and the mathematics oriented papers to Publicationes Mathematica