SAND REPORT SAND2003-2927 Unlimited Release Printed August 2003 An Overview of Trilinos Michael Heroux, Roscoe Bartlett, Vicki Howle Robert Hoekstra, Jonathan Hu, Tamara Kolda, Richard Lehoucq, Kevin Long, Roger Pawlowski, Eric Phipps, Andrew Salinger, Heidi Thornquist, Ray Tuminaro, James Willenbring and Alan Williams Sandia National Laboratories P.O. Box 5800 Albuquerque, NM 87185-1110 Prepared by Sandia National Laboratories Albuquerque, New Mexico 87185 and Livermore, California 94550 Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000. Approved for public release; further dissemination unlimited. Issued by Sandia National Laboratories, operated for the United States Department of Energy by Sandia Corporation. NOTICE: This report was prepared as an account of work sponsored by an agency of the United States Government. 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Box 5800 Albuquerque, NM 87185-1110 Abstract The Trilinos Project is an effort to facilitate the design, development, inte- gration and ongoing support of mathematical software libraries. In particular, our goal is to develop parallel solver algorithms and libraries within an object- oriented software framework for the solution of large-scale, complex multi- physics engineering and scientific applications. Our emphasis is on developing 3 TrilinosTM Overview robust, scalable algorithms in a software framework, using abstract interfaces for flexible interoperability of components while providing a full-featured set of concrete classes that implement all abstract interfaces. Trilinos uses a two-level software structure designed around collections of packages. A Trilinos package is an integral unit usually developed by a small team of experts in a particular algorithms area such as algebraic precondition- ers, nonlinear solvers, etc. Packages exist underneath the Trilinos top level, which provides a common look-and-feel, including configuration, documenta- tion, licensing, and bug-tracking. Trilinos packages are primarily written in C++, but provide some C and Fortran user interface support. We provide an open architecture that allows easy integration with other solver packages and we deliver our software to the outside community via the Gnu Lesser General Public License (LGPL) [19]. This report provides an overview of Trilinos, discussing the objectives, history, current development and future plans of the project. 4 TrilinosTM Overview Acknowledgments The authors would like to acknowledge the support of the ASCI and LDRD pro- grams that funded development of Trilinos. 5 TrilinosTM Overview Intentionally Left Blank 6 CONTENTS TrilinosTM Overview Contents Nomenclature....................................... ....................... 9 1 Background........................................ .................. 12 2 Introduction...................................... .................... 13 3 TrilinosDesignPhilosophy.......................... ................ 14 3.1 Services Provided by Trilinos . ........... 14 4 Petra and TSF: Two Special Package Collections . ......... 17 4.1 Epetra.......................................... .......... 17 4.2 ThyraandTSFExtended ............................. ........ 18 5 CommonToolsPackage: Teuchos........................ .......... 18 6 Trilinos Package Interoperability Mechanisms......... ............. 20 7 Overview of Current Package Development............... .......... 22 7.1 ThePetraObjectModel............................. ......... 22 Epetra: Essential Implementation of Petra Object Model . ........ 22 Tpetra: Templated C++ Implementation of Petra Object Model ...... 23 Jpetra: Java Implementation of Petra Object Model . ....... 23 7.2 TSF: The Trilinos Abstract Class Packages . .......... 24 7.3 AztecOO: Concrete Preconditioned Iterative Solvers . ............ 25 7.4 Belos: Generic Implementation of Krylov Methods . .......... 26 7.5 Amesos: Object-oriented Interface to Direct Solvers . ............ 26 7.6 Komplex: Solver Suite for Complex-valued Linear Systems......... 27 7.7 Ifpack: Parallel Algebraic Preconditioners . .............. 28 7.8 ML: Multi-level Preconditioner Package . ............ 28 7.9 Meros ........................................... ......... 29 7.10 NOX: Nonlinear Solver Package . .......... 30 7.11 LOCA: Library of Continuation Algorithms . ............ 31 7.12 Anasazi: Eigensolver package . ........... 31 7.13 FuturePackages ................................. .......... 32 8 Conclusions....................................... ................... 32 References......................................... ........................ 37 Appendix A Brief Overview of Some Object-Oriented Concepts ........ ............ 39 Object-oriented Programming . ............ 39 7 TrilinosTM Overview FIGURES SomeKeyOOPTerms.................................... ....... 40 Figures 1 Current collection of Trilinos Packages . .......... 15 8 FIGURES TrilinosTM Overview Nomenclature Trilinos The name of the project. Also a Greek term which, loosely translated means “a string of pearls,” meant to evoke an image that each Trilinos package is a pearl in its own right, but is even more valuable when combined with other packages. Package A self-contained collection of software in Trilinos focused on one primary class of numerical methods. Also a fundamental, integral unit in the Trilinos framework. Didasko The tutorial of Trilinos. Offers a quick introduction to several Trilinos pack- ages. It contains a printable PDF document and a variety of well-commented browsable examples that illustrate how to use Trilinos. Didasko contains examples for the following Trilinos packages: Teuchos, Epetra, EpetraExt, TriUtils, Galeri, AztecOO, IFPACK,ML, NOX, Anasazi, TPe- tra. new package A sample Trilinos package containing all of the infrastructure to install a new package into the Trilinos framework. Contains the basic directory structure, a collection of sample configuration and build files and a sample “Hello World” package. Also a website. Amesos The Direct Sparse Solver Package in Trilinos. The goal of Amesos is to make AX=B as easy as it sounds, at least for direct methods. Amesos provides clean and consistent interfaces to several popular third party libraries. Anasazi An extensible and interoperable framework for large-scale eigenvalue algo- rithms.The motivation for this framework is to provide a generic interface to a collection of algorithms for solving large-scale eigenvalue problems. AztecOO Linear solver package based on preconditioned Krylov methods. A follow-on to the Aztec solver package [46]. Supports all Aztec interfaces and function- ality, but also provides significant new functionality. Belos A Greek term meaning “arrow.” Belos is the next generation of iterative solvers. Belos solvers are written using “generic” programming techniques. In other words, Belos is written using TSF abstract interfaces and therefore has no explicit dependence on any concrete linear algebra library. Instead, Belos solvers can be used with any concrete linear algebra library that imple- ments the TSF abstract interfaces. Claps Claps is a collection of domain decomposition preconditioners and solvers. Epetra See description under ”Petra”. 9 TrilinosTM Overview FIGURES EpetraExt A set of extensions to Epetra.