Parallel (//) ELLPACK: A Problem Solving Environment for PDE Based Applications on Multicomputer Platforms

This paper presents the software architecture and implementation of the problem solving environment (PSE) IIELLPACK for modeling physical objects described by partial differenlial equations (FDEs). The scope of this PSE is broad as IIELLPACK incorporates many PDE solving systems and some of these, in (urn, include several specific PDE solving melhods. Its coverage for 1-0, 2·0 and 3-D elliptic or parabolic problems is quite broad, and it handles some hyperbolic problems. Since a PSE should provide complete support for the problem solving process, IIELLPACK also contains a large amOUnl of code to support graphical user interfaces, analytic tools, user help, domain or mesh panitioning, machine and data seleclion, visualization, and various other tasks. Its total size is well over 1 million lines of code. Its "open-ended" software architecture consists of five software layers. The top layer is an interaclive graphical interface for specifying the PDE model and its solution framework. This interface saves lhe resulr.s of the user specification in lhe form of a very high level PDE language which is lhe second layer of interface to the IfELLPACK system. This language also allows a user to specify the PDE problem and its solution framework tex.tually in a "nalural" form. In the third layer, the IIELLPACK language preprocessor generates a Fortran control program with the interfaces, caIls to specified components and libraries of lhe PDE solution framework, and functions defining lhe PDE problem. The fourth layer is an execution environment where the virtual parallel system is defined, where lhe execution mode, file system, and hardware resources are selected, and where the compilation, loading, and ex.ecution are controlled. Finally, lhe bottom layer consists of several PDE system libraries and their interfaces to lhe IfELLPACK system. The syslem employs several parallel reuse methodologies based on the decomposition of discrete geometric data to map sparse PDE compulations to parallel machines. An instance of the system is available as a Web server (Web//ELLPACK) for public use at the http://pellpack.cs.purdue.edu.