Send mail to: mgnet@cs.yale.edu for the digests or bakeoff mgnet-requests@cs.yale.edu for comments or help Current editor: Craig Douglas douglas-craig@cs.yale.edu Anonymous ftp repository: casper.cs.yale.edu (128.36.12.1) Today's editor: Craig Douglas (douglas-craig@cs.yale.edu) Volume 2, Number 2 (February 14, 1992) Happy Valentine's Day Today's topics: GMD Communications Library References Multigrid Course ------------------------------------------------------- Date: Tue, 28 Jan 92 18:03:25 GMT From: gmap21@f1euler.gmd.de (Hubert Ritzdorf) Subject: The GMD Communications Library A survey of the GMD Communications Library for Grid-Oriented Problems One important class of applications for high performance parallel computers is based on regular grid data structures. Multigrid and CFD codes using finite difference or finite volume discretizations fall into this category. As the communication parts of these programs are similar, a central communications library has been created, with subroutines covering all communication requirements of the parallel application programs (the communication of all the multigrid programs developed in Institute I1 of the GMD is performed by the Communications Library). Because this GMD Communications Library is based on the ANL/GMD Macros (PARMACS), the library and the application programs are portable between all machines for which the PARMACS are available. The GMD Communications Library is, of course, not the first subroutine library for inter-process communication on parallel machines. The philosophy of this library, however, is that it is written on a fairly high level rather than simply exchanging, for example, a send operation by a more portable construct. Instead, more complex tasks are performed by the library routines, facilitating the optimization of the underlying algorithm on the machine used. In the definition of the communications library routines, care has been taken in order that they are not designed to the special requirements of only one application. This would obviously unnecessarily restrict the range of use. Furthermore, it is important that the library supplies routines for as many communication tasks of the applications program as possible, because otherwise the user again has to write special communication routines himself. The definition of the library is a dynamic process (currently, the library contains about 40,000 lines of code); additions are made as new requirements become apparent. So far, all communication requirements of multigrid programs and similar, grid-related problems, in two- and three-dimensions on rectangular or cubic domains are covered. Often, for CFD applications, block-structured domains are used. Library routines for these more general domains have, to date, only been implemented for 2-dimensional block-structures. Currently, the Communications Library for 2- and 3-dimensional process grids performs the following tasks (among other tasks): * Creation of node processes * Exchange of grid function values along inner boundaries * Redistribution of grid functions (``agglomeration''), change of the process grid (for coarse multigrid levels). The Communications Library for 2-dimensional block-structured grids performs the following tasks (among other tasks): * Creation of node processes * Transferring the grid coordinates to the node processes * Distribution of alteration rights at block boundaries * Setting up the update sequence to exchange the grid functions along inner boundaries * Computation of the areas which have to be sent to the neighbouring blocks * Exchange of the grid functions along inner boundaries The following tasks can also be performed in a process grid application as well as in a block-structured application: * Initialization and termination of the host process * Global operations (for example additions, supremum norms, ...) over all node processes * Send of subarrays to a specific process * Node triggered abort of the distributed application * Writing messages of grid functions from the node processes * Process synchronization * Inspection of the mailbox * A Link between the Communications Library and the ANL/GMD Macros It is planned to integrate cell-centred discretization schemes and local refinements in the block-structured part of the Communications Library. The GMD Communications Library is available from the GMD (contact Hubert Ritzdorf, gmap21@f1euler.gmd.de) and from PALLAS GmbH. ------------------------------------------------------- Date: Tue, 28 Jan 92 17:47:27 GMT From: gmap21@f1euler.gmd.de (Hubert Ritzdorf) Subject: Some Papers of Possible Interest \item Brakhagen F.; Fogwell T.W.: {\it Multigrid Methods for Systems of Partial Differential Equations with Discontinuous Coefficients.} Proceedings of the Third International Conference on Hyperbolic Problems, Uppsala, Sweden, June 11--15, 1990 (B. Engquist, B. Gustafson eds.), Studentlitteratur, Lund, Sweden, 1991. \item Brakhagen F.; Fogwell T.W.: {\it Multigrid Methods for the Fully Implicit Formulation of the Equations for Multiphase Flow in Porous Media.} Proceedings of the Third European Conference on Multigrid Methods, Bonn, October 1--4, 1990, Multigrid Methods : Special Topics and Applications II, GMD-Studie Nr. 189, St. Augustin, 1991 (W. Hackbusch, U. Trottenberg eds.). \item G\"artel, U.; Ressel, K.: {Parallel Multigrid : Grid Partitioning versus Domain Decomposition.} Arbeitspapiere der GMD, Nr. 599, GMD, St. Augustin, 1991 \item Hempel, R.; Ritzdorf, H.: {\it The GMD Communications Library for Grid--Oriented Problems.} Arbeitspapiere der GMD, Nr. 589, GMD, St. Augustin, 1991 \item Hempel, R.; Ritzdorf, H.: {\it The GMD Communications Library for Grid--Oriented Problems. -- User's Reference Manual --} Internal documentation, GMD, St. Augustin, 1991 \item Joppich, W.: {\it A Multigrid Algorithm with Time-dependent, locally refined Grids for Solving the Nonlinear Diffusion Equation on a Nonrectangular Geometry - Practical Aspects.} Arbeitspapiere der GMD, Nr. 516, GMD, St. Augustin, 1991 \item Joppich, W.; Lorentz, R. A.: {\it High Order Positive, Monotone and Convex Multigrid Interpolations.} Arbeitspapiere der GMD, Nr. 558, GMD, St. Augustin, 1991 \item Lonsdale, G.; Sch\"uller, A.: {\it Parallel and vector aspects of a multigrid Navier-Stokes solver.} Arbeitspapiere der GMD, Nr. 550, GMD, St. Augustin, 1991 (submitted for publication in SIAM J. on Scientific and Statistical Computing). \item Lonsdale, G.; Sch\"uller, A.: {\it Maintaining multigrid and parallel efficiency for the Navier-Stokes equations.} Proceedings of the Conference on ``Parallel Computational Fluid Dynamics'', Stuttgart, Germany, 10-12 June 1991 (Reinsch et al., eds.), Elsevier Science Publishers B.V., Amsterdam. \item Lonsdale, G.; St\"uben, K.: {\it The LiSS Package.} Arbeitspapiere der GMD, Nr. 524, GMD, St. Augustin, 1991 \item Lorentz, R. A.; Madych, W.R.: {\it Spline Wavelets for Ordinary Differential Equations.} Arbeitspapiere der GMD, Nr. 562, GMD, St. Augustin, 1991 \item Lorentz, R. A.; Madych, W.R.: {\it Wavelets and Generalized Box Splines.} Arbeitspapiere der GMD, Nr. 563, GMD, St. Augustin, 1991 \item McBryan, O.A.; Frederickson, P.O.; Linden, J.; Sch\"uller, A.; Solchenbach, K.; St\"uben, K.; Thole, C.-A.; Trottenberg, U.: {\it Multigrid methods on parallel computers -- a survey of recent developments.} IMPACT of Computing in Science and Engineering 3, 1-75, 1991. \item Sch\"uller, A.; Solchenbach, K.; Trottenberg, U.: {\it Grid partitioning for CFD applications.} Proceedings of the Conference on ``Parallel Computational Fluid Dynamics'', Stuttgart, Germany, 10-12 June 1991 (Reinsch et al., eds.), Elsevier Science Publishers B.V., Amsterdam. \item Sch\"uller, A.: {\it Parallelizing particle simulations based on the Boltzmann equation.} Arbeitspapiere der GMD, Nr. 557, GMD, St. Augustin, 1991 (to be published 1992 in Parallel Computing). ------------------------------------------------------- Date: Tue, 4 Feb 92 12:42:14 GMT From: gmap21@f1euler.gmd.de (Hubert Ritzdorf) Subject: Multigrid Course Multigrid Course 1992 -- GMD-Sankt Augustin The GMD will give a multigrid course on June 22 - 26, 1992 at Sankt Augustin near Bonn, Germany. The principal lecturer is Professor Achi Brandt from the Weizmann Institute, Rehovot, Israel, one of the pioneers of multigrid. The other lecturers are members of the GMD multigrid research group. The topics of this course will cover the basic principles of multigrid, recent developments and applications. The main scope of the course is to provide with an understanding of multigrid. The visitor will, at the end of the course, be able to write a multigrid program for model problems. Additionally, the course will supply with an overview of multigrid application and recent research activities. The course is especially designed for all those which have to solve partial differential equations in practice. Multigrid, or more general multilevel computational methods have evolved into an independent discipline by itself, interacting with numerous engineering application areas and impacting fundamental developments in several sciences. The recent past shows an increased development of multilevel solvers for various areas, including: aerodynamics, atmospheric and oceanic research, structural mechanics, robotics, quantum mechanics, astrophysics, condensed matter, VLSI design, and tomography. This enormous spectrum was opened by the following facts: The typical multilevel algorithm uses local processing on each scale of the problem, with inter-scale interactions. As a result, fine scales can be employed very sparingly, and sometimes only at special or representative small regions. The theory states that a multigrid solution is generally obtained in a time directly proportional to the number of unknowns on serial computers. As indicated by the above examples, further research and developments showed the potential of the multigrid principle which allows the application of multigrid algorithms and multigrid ideas to highly complex problems. The inherent locality of the multigrid components allows a very efficient parallelization with nearly optimal speed up. Recent research activities have verified this for a wide class of parallel machines. For further information, please contact: Barbara Steckel, Wolfgang Joppich Institut f\"ur Methodische Grundlagen (I1/T) Gesellschaft f\"ur Mathematik und Datenverarbeitung (GMD) Postfach 1316 W-5205 Sankt Augustin 1 Federal Republic of Germany Phone: (0)2241 14 2768 or - 2748 Fax: (0)2241 14 2460 Email: gmap16@dbngmd21.bitnet ------------------------------------------------------- End of MGNet Digest **************************