Dietmar Ratz – författare

PASCAL-XSC (PASCAL-eXtension for Scientific Computation) ist eine Erweiterung der weitverbreiteten Programmiersprache PASCAL. Sie verfolgt das Ziel, das Programmieren, insbesondere im Bereich technisch-wissenschaftlicher Anwendungen, durch zusätzliche Sprachkonzepte wie Module, dynamische Felder und Operatoren erheblich zu vereinfachen. Eine optimale Arithmetik mit hochgenauen Standardfunktionen und exakter Ausdrucksauswertung ermöglicht eine automatisierte, zuverlässige Kontrolle der berechneten Ergebnisse. Damit unterstützt PASCAL-XSC die Entwicklung von Routinen mit automatischer Ergebnisverifikation. Mittels der Compiler-Implementierung in C kann PASCAL-XSC auf PC's, Workstations, Großrechnern und Supercomputern gleichermaßen eingesetzt werden. In dem vorliegenden Lehr- und Handbuch wird PASCAL-XSC vollständig beschrieben. Zur praktischen Verwendung und zum leichteren Kennenlernen und Vertrautwerden mit den über PASCAL hinausgehenden neuen Sprachelementen ist ein ausführlicher Abschnitt mit Übungsaufgaben und Lösungen aufgenommen worden. Ein kompletter Satz von Syntaxdiagrammen, sowie ausführliche Register und Verzeichnisse schließen dieses Buch ab.

This manual describes a PASCAL extension for scientific computation with the short title PASCAL-XSC (PASCAL eXtension for Scientific Computation). The language is the result of a long term effort of members of the Institute for Applied Mathematics of Karlsruhe University and several associated scientists. PASCAL­ XSC is intended to make the computer more powerful arithmetically than usual. It makes the computer look like a vector processor to the programmer by providing the vector/matrix operations in a natural form with array data types and the usual operator symbols. Programming of algorithms is thus brought considerably closer to the usual mathematical notation. As an additional feature in PASCAL-XSC, all predefined operators for real and complex numbers and intervals, vectors, matrices, and so on, deliver an answer that differs from the exact result by at most one rounding. Numerical mathematics has devised algorithms that deliver highly accurate and automatically verified results by applying mathematical fixed point theorems. That is, these computations carry their own accuracy control. However, their imple­ mentation requires arithmetic and programming tools that have not been available previously. The development of PASCAL-XSC has been aimed at providing these tools within the PASCAL setting. Work on the subject began during the 1960's with the development of a general theory of computer arithmetic. At first, new algorithms for the realization of the arithmetic operations had to be developed and implemented.

As suggested by the title of this book Numerical Toolbox for Verified Computing, we present an extensive set of sophisticated tools to solve basic numerical problems with a verification of the results. We use the features of the scientific computer language PASCAL-XSC to offer modules that can be combined by the reader to his/her individual needs. Our overriding concern is reliability - the automatic verification of the result a computer returns for a given problem. All algorithms we present are influenced by this central concern. We must point out that there is no relationship between our methods of numerical result verification and the methods of program verification to prove the correctness of an imple~entation for a given algorithm. This book is the first to offer a general discussion on • arithmetic and computational reliability, • analytical mathematics and verification techniques, • algorithms, and • (most importantly) actual implementations in the form of working computer routines. Our task has been to find the right balance among these ingredients for each topic. For some topics, we have placed a little more emphasis on the algorithms. For other topics, where the mathematical prerequisites are universally held, we have tended towards more in-depth discussion of the nature of the computational algorithms, or towards practical questions of implementation. For all topics, we present exam­ ples, exercises, and numerical results demonstrating the application of the routines presented.