Send mail to: mgnet@cs.yale.edu for the digests mgnet-requests@cs.yale.edu for comments or help Anonymous ftp repository: casper.cs.yale.edu (128.36.12.1) ftp.cerfacs.fr (138.63.200.33) World Wide Web: http://na.cs.yale.edu/mgnet/www/mgnet.html or http://www.cerfacs.fr/~douglas/mgnet.html Today's editor: Craig Douglas (douglas-craig@cs.yale.edu) Volume 5, Number 11 (approximately November 30, 1995) Today's topics: Preprints by Zhang et al Preprints by Pasciak et al Papers by Shapira UG Software available CFD short course Book by D'yakonov Faculty opening at CU-Denver Faculty opening at Virginia Tech Updated preprint by Douglas ------------------------------------------------------- Date: Mon, 20 Nov 1995 13:53:32 -0500 From: Jun Zhang Subject: Preprints by Zhang et al An Accurate and Stable Multigrid Method for Convection-Diffusion Equations Murli M. Gupta, Jules Kouatchou and Jun Zhang Department of Mathematics The George Washington University Washington, DC 20052, USA Abstract: We introduce a high-order compact difference scheme with multigrid algorithm to solve the convection-diffusion equations with constant coefficients. This high-order discretization scheme is shown to be more accurate and stable than the usual five-point discretization scheme. It solves the convection- diffusion equations directly without using any preconditioner or adding any artificial dissipation terms. This method is shown to converge faster than some of the existing methods and to achieve higher accuracy. Numerical experiments are presented to validate the conclusions. Editor's Note: in mgnet/papers/Gupta-Kouatchou-Zhang/con_diff.ps.gz and ------------- mgnet/papers/Gupta-Kouatchou-Zhang/con_diff.abs. Acceleration of Five-point Red-Black Gauss-Seidel in Multigrid for Poisson Equation Jun Zhang Department of Mathematics The George Washington University, Washington, DC 20052, USA Abstract: A new relaxation analysis and two acceleration schemes are proposed for the five-point Red-Black Gauss-Seidel smoothing in multigrid for solving two dimensional Poisson equation. For a multigrid V cycle, we discovered that under-relaxation is applicable to restriction half cycle and over-relaxation is applicable to interpolation half cycle. Numerical experiments using modified multigrid V cycle algorithms show that our simple acceleration schemes accelerate the convergence rate by as much as 34% with negligible cost. This result is contrary to the existing belief that SOR is not suitable for using as a smoother in multigrid for Poisson equation, because the gain in computational savings would not pay for the cost of implementing it. More important is the idea of employing different parameters to accelerate the reduction of low and high frequency errors separately. Our discovery offers a new way for SOR smoothing in multigrid. Editor's Note: in mgnet/papers/Zhang/sor.ps.gz and ------------- mgnet/papers/Zhang/sor.abs. ------------------------------------------------------- Date: Mon, 6 Nov 1995 08:47:05 -0500 From: pasciak@jep.das.bnl.gov (Joe Pasciak) Subject: Preprints by Pasciak et al I put the papers and abstracts into incoming/pasciak. Some of these papers are not necessarily directly multigrid related but all have something to do with preconditioning so they may be of some interest to members of the net. Joe Editor's Note: I moved all 7 of the new contributions to the directory ------------- mgnet/papers/Pasciak-et-al. ------------------------------------------------------- Date: Tue, 14 Nov 1995 22:05:44 -0700 From: Yair Shapira Subject: Papers by Shapira I put one more paper on mgnet. I also put an updated version of the paper tlanalysis.ps.gz. Please put them in mgnet/papers/Shapira. Improved Black Box Multigrid for Definite and Indefinite Problems Yair Shapira Computer Science Department, Technion, Haifa 32000, Israel e-mail: yairs@lanl.gov. Abstract A two-level analysis method for certain separable problems is introduced. Unlike standard two-level analysis methods, based on Fourier analysis, it is based on spectral analysis, hence applicable to non-normal problems and to certain problems with variable coefficients. It motivates the definition of improved versions of Black Box Multigrid for diffusion problems with discontinuous coefficients and indefinite Helmholtz equations. For anisotropic problems, it helps in choosing suitable implementations for frequency decomposition multigrid methods. For highly indefinite problems, it provides a way to choose a suitable mesh size for the coarsest grid used. Numerical experiments confirm the analysis and show the advantage of the present methods. Editor's Note: in mgnet/papers/Shapira/bbox.ps.gz and ------------- mgnet/papers/Shapira/bbox.abs. update is mgnet/papers/Shapira/tlanalysis.ps.gz. ------------------------------------------------------- Date: Mon, 27 Nov 1995 From: Peter Bastian Subject: UG Software available Dear colleagues, we are happy to announce the availability of version 3.1 of our software "UG" (short hand for Unstructured Grids). UG is a flexible software library for the development of adaptive multigrid methods on unstructured meshes. The main idea of UG was to implement most parts in a problem-independent way, so that the software can be reused for many different applications. The main features of the problem-independent part are: * 2D (triangles, quadrilaterals) and 3D (tetrahedra) unstructured meshes * tree-based local refinement and coarsening * user-definable number of degrees of freedom in nodes, edges, faces and elements (conforming, non-conforming and mixed finite-elements can be implemented) * BLAS and iterative methods (smoothers, multigrid, cg) * powerful script language * Multi-window graphical user interface for X11 and Macintosh. No special graphics libraries required * 1000 pages of documentation (man-pages, postscript) * Parallel version with reduced functionality available (2D, degrees of freedom only in nodes, dynamic load balancing, interfaces for PVM, NX, PARIX, T3D, MPI) Applications in the current distribution include: * 2D scalar diffusion equation with linear conforming and nonconforming finite-elements * 2D linear elasticity with conforming and non-conforming finite-elements * 2D incompressible, stationary Navier-Stokes equations * 3D convection-diffusion equation Many other applications are currently being developped on the basis of UG. UG is available for free for all non-profit organizations. For further information use: * World Wide Web: http://www.ica3.uni-stuttgart.de/~ug * FTP: ftp.ica3.uni-stuttgart.de/pub/ug/ug3.1 * email: ug@ica3.uni-stuttgart.de Editor's Note: I put a copy in mgnet/Codes/ug (version 3.1.2) at both Yale ------------- and CERFACS. ------------------------------------------------------- Date: Fri, 10 Nov 1995 09:04:21 -0700 From: cliu@carbon.cudenver.edu (Chaoqun Liu) Subject: CFD short course ADVANCES IN COMPUTATIONAL FLUID DYNAMICS A 5-Day Short Course Announcement Louisiana Tech University, Ruston, Louisiana June 24 - 28, 1996 The Louisiana Tech University will host a 5-day CFD short course in the summer of 1996. A number of leading researchers will give lectures on recent advances in CFD. Several advanced teaching and research codes for incompressible flow, direct numerical simulation for flow transition, and numerical combustion with detailed chemistry will be described and distributed to all attendants for free. Anyone who is interested in CFD and has basic multigrid and CFD knowledge, including faculty, graduate students, scientific researchers, government agents, and industrial scientists and engineers, are welcome to attend. The registration fee is at a discounted level of $350 (group rate is $250 and student rate is $150), and it covers all lecture notes, floppy disks with computational codes, a reception, and a formal dinner. The lectures include: Multigrid and multilevel adaptive methods First-order system least square (FOSLS) Preconditioning for low speed flow Central difference, R-K scheme, and residual smoothing Boundary conditions for time dependent flows Upwind differencing - principles and recent development Advanced turbulence models Fast Navier-Stokes solver High-order grid generation Direct numerical simulation for complex geometry Non-reflecting outflow boundary condition Multilevel grid dissipation Numerical simulation for turbulent combustion with detailed chemistry Numerical pollutant prediction The speakers include: Dr. L. Sakell (US Air Force Office of Scientific Research) Dr. A. Brandt (Weizmann Institute, Israel) Dr. E. Turkel (Tel Aviv University, Israel) Dr. P. Roe (University of Michigan) Dr. S. McCormick (University of Colorado at Boulder) Drs. T-H Shih and J. Zhu (NASA Lewis Research Center) Dr. C-H Sung (Navy David Taylor Research Center) Dr. C. Liu ( Louisiana Tech University) Drs. Z. Liu, X. Zheng, and C. Liao ( Louisiana Tech University) If you are interested in this short course, please fill out the attached form and email it back to cliu@math.latech.edu or send it by regular post to: Prof. Chaoqun Liu ACFD Short Course Chair Department of Mathematics and Statistics Louisiana Tech University P.O. Box 3189, Ruston, LA 71272-0001 Tel : (318) 257-2538 Fax : (318)257-3935 email : cliu@math.latech.edu http://www.math.latech.edu/~cliu For more information please go to: http://www.math.latech.edu/~cliu or call Dr. Chaoqun Liu at (318) 257-2924. ________________________________________________________________________ Name _______________ Mailing Address : _____________________________________________ _____________________________________________ _____________________________________________ Day Phone Number : __________________________ Fax Number: __________________________ Email Address : __________________________ I am interested in the ACFD short course. Please send me the ------------------------------------------------------- Date: Tue, 21 Nov 95 16:05:53 +0300 (MSK) From: dknv@cmc.msk.su (dknv) Subject: Book by D'yakonov Dear Craig, I am pleased to inform you that CRC Press published my book " Optimization in Solving Elliptic Problems" (about 600 pages) a few weeks ago. They did an excellent job and it seems that the book is not superexpansive (about 80 $). It is possible to contact the Orders department directly by e-mail (orders@crcpress.com) . I am asking you to pass the information to other interested people at your "vicinity". Best wishes. Gene D'yakonov. ------------------------------------------------------- Date: Thu, 2 Nov 1995 18:02:04 -0700 From: aknyazev@tiger.cudenver.edu (Andrew Knyazev) Subject: Faculty opening at CU-Denver University of Colorado at Denver Department of Mathematics The Department of Mathematics at the University of Colorado at Denver is seeking to fill two tenure-track positions at the rank of Assistant Professor, beginning August 1996. Positions are contingent on budgetary approval. We offer B.S., M.S. and Ph.D. degrees with optional focus in one of six areas: computational mathematics, discrete mathematics, engineering mathematics, operations research, probability, and statistics. These also comprise active areas of research of our resident faculty. Applicants are expected to show strong potential for research and teaching and have a commitment to professional service. Applicants must have, or expect to receive by next August, a Ph.D. in mathematics or a related discipline. In general, we seek qualified applicants in one of the focus areas and prefer someone who can interface with two or more areas. For these positions, the areas of greatest interest are applied probability or statistics, and computational mathematics. However, we shall consider applications with another focus in applied mathematics. To apply, please send a current vita, list of publications, a statement of research plans and goals, a statement of teaching philosophy, and arrange to have three letters of recommendation sent to: Burt Simon, Search Committee Chair Mathematics Department - Campus Box 170 University of Colorado at Denver P.O. Box 173364 Denver, CO 80217-3364 Our fax number is 303-556-8550. For more information on our department and university visit our web site at http://www-math.cudenver.edu. We will begin screening applications December 15, 1995. The University of Colorado at Denver is committed to enhancing the diversity of its administration, faculty and staff, and to program access for persons with disabilities, and invites and strongly encourages nominations of and applications from women, members of ethnic and racial minorities, veterans, and people with disabilities. Alternative formats of this ad or job description are available upon request. ------------------------------------------------------- Date: Mon, 20 Nov 1995 09:39:49 -0500 From: Christopher Beattie Subject: Faculty opening at Virginia Tech We posted this on nanet a few weeks ago but want to make sure we have healthy representation of multigrid types in our applicant pool. Virginia Polytechnic Institute and State University Department of Mathematics Applications are solicited for a tenure-track assistant professorship in numerical analysis. Candidates must have a PhD in mathematics or equivalent, with a strong record or demonstrated potential in research and teaching. We seek candidates who will augment an existing faculty focus in numerical treatment of PDEs, optimization, and computational linear algebra. Send a letter of application, curriculum vitae, summary of research plans, together with four letters of recommendation (one of which addresses teaching skills), to: Numerical Analysis Search Committee, Department of Mathematics, Virginia Tech, Blacksburg, VA 24061-0123. Review of applications will begin on December 20, 1995 and will continue until the position is filled. Virginia Tech has a strong commitment to the principle of diversity and, in that spirit, seeks a broad spectrum of candidates including women, minorities, and people with disabilities. Individuals with disabilities desiring accommodations in the application process should contact Christopher Beattie, Department of Mathematics, 540-231-6536 (TDD/PC 1-800-828 1120- Voice 1-800-828-1140). ------------------------------------------------------- Date: Mon, 27 Nov 1995 08:08:08 -0500 From: Craig Douglas Subject: Updated preprint by Douglas A Review of Numerous Parallel Multigrid Methods Craig C. Douglas IBM T. J. Watson Research Center Yale University Computer Science Department CERFACS Abstract Multigrid methods originated earlier this century, in the personnel computing era. Someone who needed to compute an approximation to the solution of a partial differential equation during that era would fill a room with people. After using very simple mechanical calculators to compute parts of the approximation, these people would pass their parts to the other people in the room who needed them. Except for the very different time scales and approximate solution accuracy, this process is similar to computing on today's distributed memory parallel computers. Parallel multilevel methods are shown to be the natural precursors to standard multilevel methods based on the personnel computing era of earlier this century. They are also the natural successors to standard multilevel methods in the age of computers. What makes six parallel multilevel methods practical and impractical is discussed in the context of the three algorithms that encapsulate them. Appears in slightly edited form in SIAM News, V.25, N.3, May, 1992. This will appear in Applications on Advanced Architecture Computers Edited by Greg Astfalk Available spring 1996 Approx. 350 pages Softcover ISBN 0-89871-368-4 List Price $35.00 SIAM Member Price $28.00 Order Code OT53 Editor's Note: in mgnet/papers/Douglas/para-mg.ps.gz and ------------- mgnet/papers/Douglas/para-mg.abs. ------------------------------ End of MGNet Digest **************************