11330765
Transparent filtering of streams in GLADE
Note: Also available as Technical Report EPFL 97/241 Reference LGL-CONF-1997-009 Record created on 2005-09-20, modified on 2016-08-08
62754021
Transparent replication for fault tolerance in distributed Ada 95
In this paper we present the foundations of RAPIDS ("Replicated Ada Partitions In Distributed Systems"), an implementation of the PCS supporting the transparent replication of partitions in distributed Ada 95 using semi-active replication. The inherently non-deterministic executions of multi-tasked partitions are modeled as piecewise deterministic histories. I discuss the validity and correctness of this model of computation and show how it can be used for efficient semi-active replication. The R APIDS prototype ensures that replicas of a partition all go through the same history and are hence consistent.
196094
Integrating object-oriented programming and protected objects in Ada 95
Integrating concurrent and object-oriented programming has been an active research topic since the late 1980's. There is a now a plethora of methods for achieving this integration. The majority of approaches have taken a sequential object-oriented language and made it concurrent. A few approaches have taken a concurrent language and made it object-oriented. The most important of this latter class is the Ada 95 language, which is an extension to the object-based concurrent programming language Ada 83. Arguably, Ada 95 does not fully integrate its models of concurrency and object-oriented programming. For example, neither tasks nor protected objects are extensible. This article discusses ways in which protected objects can be made more extensible.
31197886
Object-Oriented Programming and Protected Objects in Ada 95
Integrating concurrent and object-oriented programming has been an active research topic since the late 1980s. The majority of approaches have taken a sequential object-oriented language and made it concurrent. A few approaches have taken a concurrent language and made it object-oriented. The most important of this latter class is the Ada 95 language which is an extension to the object-based concurrent programming language Ada 83. Arguably, Ada 95 does not fully integrate its models of concurrency and object-oriented programming. This paper discusses ways in which protected objects can be made more extensible.
1643372
Fault Tolerance by Transparent Replication for Distributed Ada 95
This paper presents the foundations of RAPIDS ("Replicated Ada Partitions In Distributed Systems"), an implementation of the Distributed Systems Annex E incorporating the transparent replication of partitions in distributed Ada 95 applications. RAPIDS is a replication manager for semi-active replication based on a piecewise deterministic computation model. It guarantees replica consistency for arbitrary Ada 95 partitions despite the inherent non-determinism of multitasking, offering k-resilient partitions. The RAPIDS prototype is implemented for the GNAT compiler and evolved from its PCS, Garlic.
1084067
On exceptions as first-class objects in Ada 95
This short position paper argues that it might be beneficial to try to bring the exception model of Ada 95 more in-line with the object-oriented model of programming. In particular, it is felt that exceptions --- being such an important concept for the development of fault-tolerant software --- have deserved a promotion to first-class objects of the language. It is proposed to resolve the somewhat awkward dichotomy of exceptions and exception occurrences as it exists now in Ada 95 by treating exceptions as (tagged) types, and exception occurrences as their instances.
19107527
Investigating DEs with CRACK and related programs
The aim of the package to be described is to try modularizing the investigation of differential equations for which there are no complete algorithms available yet. All, that is available for such problems are algorithms for special situations, e.g. when first integrals with a simple structure exist (e.g. polynomial in first derivatives) or when the problem has infinitesimal symmetries. In all such cases, finally a system of differential equations has to be solved which is overdetermined in the sense that more conditions have to be satisfied than there are unknown functions. To do a variety of such investigations efficiently, like a symmetry analysis, application of symmetries, determination of first integrals, differential factors, equivalent Lagrangians, the strategy is to have one package (CRACK) for simplifying DEs and solving simple DEs as effective as possible and to use this program as the main tool for all the above mentioned investigations. For each investigation there is then only a short program necessary to just formulate the necessary conditions in form of an overdetermined DE-system and to call CRACK to solve this, possibly in a number of successive calls. The examples below shall indicate the range of possible applications.
1703030
Optimizing GoTools' Search Heuristics using Genetic Algorithms
GoTools is a program which solves life & death problems in the game of Go. This paper describes experiments using a Genetic Algorithm to optimize heuristic weights used by GoTools' tree-search. The complete set of heuristic weights is composed of different subgroups, each of which can be optimized with a suitable fitness function. As a useful side product, an MPI interface for FreePascal was implemented to allow the use of a parallelized fitness function running on a Beowulf cluster. The aim of this exercise is to optimize the current version of GoTools, and to make tools available in preparation of an extension of GoTools for solving open boundary life & death problems, which will introduce more heuristic parameters to be fine tuned.
23941957
Model Checking
Die Gewährleistung der korrekten
Funktionsweise von Hard- und Software ist ein entscheidender
Faktor bei der heutigen Systementwicklung. Dies trifft ganz
besonders auf das Gebiet der sog. „sicherheitskritischen“
Systeme zu, bei dem ein Systemversagen Menschenleben gefährden
kann.
9140187
The integration of systems of linear PDEs using conservation laws of syzygies
A new integration technique is presented for systems of linear partial differential equations (PDEs) for which syzygies can be formulated that obey conservation laws. These syzygies come for free as a by-product of the differential Grobner basis computation. Compared with the more obvious way of integrating a single equation and substituting the result in other equations the new technique integrates more than one equation simultaneously and therefore introduces temporarily fewer new functions of integration that in addition depend on fewer variables. Especially for high order PDE systems in many variables the conventional integration technique may lead to an explosion of the number of functions of integration which is avoided with the new method. A further benefit is that redundant free functions in the solution are either prevented or that their number is at least reduced.
30440565
Ein optisches Meßsystem zur Echtzeitanalyse von Konturen mit der PLL-Schaltung
Mit einer einfachen analogen Phasenmestechnik, der PLL-Schaltung, lassen sich Phasenmessungen mit hoher Genauigkeit in Echtzeit realisieren. Insbesondere in optischen Messystemen, in denen mit einer Phasenbestimmung aus einem harmonischen Intensitatsmuster die gesuchte physikalische Mesgrose extrahiert werden mus, stellt die hier vorgestellte Methode eine lohnende Alternative zu den bekannten digitalen Auswertemethoden dar. Dabei entfallen sowohl die Beschrankung auf statische Phasenbilder sowie Problematiken bei der Phasenentfaltung. Die Konturmessung an einem Kalibrierkor per sowie ein Versuch zur Bestimmung des Kriechverhaltens eines PE-Schaumes werden als Beispielmessungen vorgestellt.