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PDELAN: A MESH OPERATOR VARIANT OF FORTRAN

IP.com Disclosure Number: IPCOM000128357D
Original Publication Date: 1974-Dec-31
Included in the Prior Art Database: 2005-Sep-15
Document File: 14 page(s) / 38K

Publishing Venue

Software Patent Institute

Related People

John Gary: AUTHOR [+3]

Abstract

The objective of this language, which we call PDELAN, is to facilitate the coding of finite difference schemes for partial differ- ential equations. The aspect of these codes which we have emphasized is the difference equations.. An operator notation is provided so that the equations can be written as the numerical analyst frequently invites them prior to translation into.a program. That is U2 = Ul + DLT * DMC(Ul) where DXX represents the operator

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

PDELAN: A MESH OPERATOR VARIANT OF FORTRAN

by John Gary

Department of Computer Science University of'Colorado Boulder, Colorado Report #CU-CS- 049-74 August 1974

This design was performed under an ARPA Grant AFOS-74-2732

1. Introduction.

The objective of this language, which we call PDELAN, is to facilitate the coding of finite difference schemes for partial differ- ential equations. The aspect of these codes which we have emphasized is the difference equations.. An operator notation is provided so that the equations can be written as the numerical analyst frequently invites them prior to translation into.a program. That is U2 = Ul + DLT * DMC(Ul) where DXX represents the operator

(Equation Omitted)

and DLT = At. Implicit difference schemes can also be written in this opera-tor notation. The set up and solution of the resulting linear systems will be handled automatically. This treat ment of implicit schemes is the most powerful facility within PDkLAN.

The language is a dialect of Fortran rather than an extension. The conditional and iterati,)n commands are taken from PASCAL and thus allow a better structured progrqrming style than Fortran. These include

(Equation Omitted)

The language is coupled with a macro preprocessor which allows a topdown program- ming style [4]. The language is implemented as a preprocessor to Fortran. This is similar to the approach taken by Gear for a PL/I like language [5].

An earlier version ~f PDELAN was implemented at NCAR in 1971 [1]. The finite.difference language ha- received only light use; however, we feel this may be due to deficiencies in the earlier version which we can eliminate. Also, implicit schemes could not be treated with the previous version. In any case a language like this is intended for a specialized use and will apply to a small percentage of jobs even in-a computing center which does much continuous simulation.

Graphics and file management capability should be provided in a language for PDE problems. The earlier version does contain a sophisticated set of high level graphics commands, but no file management commands (2]. However, our effort concentrates on the difference equations and the macro preprocessor.

2. The basic language.

University of Colorado Page 1 Dec 31, 1974

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PDELAN: A MESH OPERATOR VARIANT OF FORTRAN

In this section we describe the basic set of instructions available in PDELAN. The syntax is somewhat different than in FORTRAN. The declarations are nested. For example, variable declarations are placed within the scope of a COMMON block in order to declare them,as COMMON variables. The conditional statements are similar to those in PASCAL. The 1/0 statements are similar to FORTRAN. An end-of-card is an end-of-statement unless the statement is continued. Our objective is to provide a structured base for the mesh operator constructs, but with minimal departure from FORTRAN. We proceed to a de...