PELLPACK - A PROBLEM-SOLVING ENVIRONMENT FOR PDE-BASED APPLICATIONS ON MULTICOMPUTER PLATFORMS

This article presents the software architecture and implementation of the problem-solving environment (PSE) PELLPACK for modeling physical o bjects described by partial differential equations (PDEs). The scope o f this PSE is broad, as PELLPACK incorporates many PDE solving systems , and some of these, in turn, include several specific PDE solving met hods. Its coverage for 1D, 2D, and 3D elliptic or parabolic problems i s quite broad, and it handles some hyperbolic problems. Since a PSE sh ould provide complete support for the problem-solving process, PELLPAC K also contains a large amount of code to support graphical user inter faces, analytic tools, user help, domain or mesh partitioning, machine and data selection, visualization, and various other tasks. Its total size is well over 1 million lines of code. Its open-ended software ar chitecture consists of several software layers. The top layer is an in teractive graphical interface for specifying the PDE model and its sol ution framework. This interface saves the results of the user specific ation in the form of a very high level PDE language which is an altern ative interface to the PELLPACK system. This language also allows a us er to specify the PDE problem and its solution framework textually in a natural form. The PELLPACK language preprocessor generates a Fortran control program with the interfaces, calls to specified components an d libraries of the PDE solution framework, and functions defining the PDE problem. The PELLPACK program execution is supported by a high-lev el tool where the virtual parallel system is defined, where the execut ion mode, file system, and hardware resources are selected, and where the compilation, loading, and execution are controlled. Finally, the P ELLPACK PSE integrates several PDE libraries and PDE systems available in the public domain. The system employs several parallel reuse metho dologies based on the decomposition of discrete geometric data to map sparse PDE computations to parallel machines. An instance of the syste m is available as a Web server (WebPELLPACK) for public use at http:// pellpack.cs.purdue.edu.