|
|
Home >
Computer Science and Mathematics Division
Seminar Series
The Computer Science and Mathematics Division Seminar Series is a platform to bring in scientists performing pre-eminent work of interest to the Division. The goal of the main portion of the series is to keep staff current on computer science and mathematics research and foster external collaboration. There is an effort by the committee to bring in a wide variety of speakers covering some form of the development and/or application of numerical methods. The seminars are typically held the first Tuesday of the month in the JICS auditorium at 2pm. Occasionally, the schedule is varied to accommodate speaker's schedules and such changes are noted with the seminar announcement.
Current Schedule for the 2007-2008 Season
Date |
Speaker |
Affiliation |
Abstract/Presentation |
October 17, 2007 |
Mike Heroux |
Sandia National Lab |
Abstract/Presentation/Video (87Mb) |
November 6, 2007 |
Michael Fraizer |
University of Tennessee |
Abstract/Presentation/Video (80Mb) |
December 13, 2007 |
Yvon Maday |
University of Paris |
Abstract/Presentation/Paper |
January 8, 2008 |
Jim Morel |
Texas A&M |
Abstract/Presentation |
February 5, 2008 |
Sameer Shende |
University of Oregon |
Abstract/Presentation |
March 4, 2008 |
Tony Ingraffea |
Cornell |
Abstract /Presentation |
April 4, 2008 |
Boyce Griffith |
Courant Institute, NYU |
Abstract /Presentation |
May 6, 2008 |
Mary Wheeler |
University of Texas, Austin |
Abstract |
June 2, 2008 |
Miron Livny |
University of Wisconsin |
Abstract / Presentation A / Presentation B |
June 10, 2008 |
Faith Ann Heinsch |
University of Montana |
Abstract |
June 24, 2008 |
Marcos Heil Costa |
Federal University of Viçosa, Brazil |
Abstract |
July 8, 2008 |
Michael Mahoney |
Yahoo Research Labs |
Speaker Information / Presentation |
July 29, 2008 |
Roland Glowinski |
University of Houston |
Bio |
August 7, 2008 |
Jack Dongarra |
University of Tennessee |
More Information |
August 22, 2008 |
Homer Walker |
Worcester Polytechnic Institute |
Abstract / Presentation |
September 18, 2008 |
Ricardo Nochetto |
Univ. of Maryland at College Park |
Abstract |
October 2008 |
Tim Kelley |
NC State University |
Speaker Information |
November 6, 2008 |
Damian Rouson |
Sandia California |
Speaker Information |
If you'd like to become involved in the seminar series, or have suggestions for speakers,
please contact Kate Evans.
Other Lectures of Interest
MARCH
PICMSS: An Equation-Based Parallel PDE Solver Platform
Kwai Wong (Joint Institute of Computational Sciences)
Monday, March 31, 2008
2:00 pm, Research Office Building (5700), Room D-307
Contact Phil Andrews (andrewspl@ornl.gov or 865.241.0080) for more information
Show/Hide Abstract
The presentation will focus on the development of a parallel finite element computational platform called PICMSS, Parallel Interoperable Computational Mechanics System Simulator. PICMSS provides an equation-based interface which allows users describe their specific problems in explicit differential/algebraic forms. The talk will demonstrate the functionalities of the platform, showcase some results, and proceed to discuss some challenges and requirements running on future petascale machine. Kwai Wong is a Research Scientist at the Joint Institute for Computational Sciences, UTK/ORNL and also a Consultant for the User Assistance Group for the National Center for Computational Sciences at ORNL.
Improving Operating System Support for Concurrent I/O
Chuanpeng Li (University of Rochester)
Thursday, March 6, 2008
Bldg. 5700, Room L202
Contact Phil Roth (rothpc@ornl.gov) for more information
Show/Hide Abstract
Modern computing systems become increasingly data-driven. Concurrent I/O
is a commonplace in data-intensive server systems and parallel computing
systems. In this talk, I will introduce two techniques we proposed for
improving OS support for concurrent I/O. First, during concurrent I/O
workloads, frequent disk head switching between multiple I/O streams may
severely affect I/O efficiency. Aggressive prefetching can improve the
granularity of sequential data access, but it comes with a higher risk
of fetching unneeded data. We propose a competitive prefetching strategy
that controls prefetching depth so that the overhead of disk I/O switch
and unnecessary prefetching are balanced. Second, concurrent I/O systems
may contain a large amount of prefetched data in memory. Traditional
access-history based page reclamation methods are not effective for
prefetched pages. We propose a heuristic-based OS-level scheme that can
manage prefetch memory more efficiently.
Beyond this work, I will also briefly introduce some of my other
research efforts with my colleagues, including I/O system performance
debugging and operating system exploitation of processor hardware event
counters.
FEBRUARY Show/Hide Seminars
Numerical simulation of particle clustering for particulate flow in a spinning cylinder
Professor Rowland Glowinski
Tuesday, February 12, 2008
University of Tennessee
Mathematics Colloquium
Ayres Hall Room 214
3:40 - 4:30p.m.
Contact Daniel Pack (241-6647) for more information
Show/Hide Abstract
The main goal of this lecture is to address the numerical simulation of a phenomenon which has been observed experimentally, namely: the clustering of particles in sub-populations of essentially equal size when a circular cylinder containing a mixture rigid solid particles / incompressible viscous fluid spins with a sufficiently large angular velocity. The numerical simulator relies on the combination of (i) a time discretization by operator-splitting; (ii) a fictitious domain method allowing a uniform mesh based finite element approximation (of the Bercovier-Pironneau type) in three space dimensions. The results of our numerical simulations are consistent with the experimental ones and show that, indeed, particle clustering takes place when the spinning angular velocity n is sufficiently large.
Simulating Subsurface Flow and Reactive Transport using Ultrascale Computers
Richard Mills February 19, 2008
Building 1505, D. J. Nelson Auditorium
2:00 - 3:00 p.m.
If you would like to meet with Richard, please contact Beth Baily at 574-7301.
Show/Hide Abstract
To provide true predictive utility, subsurface simulations often must accurately resolve--in three dimensions--complicated, multi-phase flow fields in highly heterogeneous geology with numerous chemical species and complex chemistry. This task is especially daunting because of the wide range of spatial scales involved--from the pore scale to the field scale--ranging over six orders of magnitude, and the wide range of time scales ranging from seconds or less to millions of years. This represents a true "Grand Challenge" computational problem, requiring not only the largest-scale ("ultrascale") supercomputers, but accompanying advances in algorithms for the efficient numerical solution of systems of PDEs using these machines, and in mathematical modeling techniques that can adequately capture the truly multi-scale nature of these problems.
In this talk, Richard will describe some of the specific challenges involved in simulating subsurface reactive flows using ultrascale supercomputers and discuss how they are being addressed in the development of the computer code PFLOTRAN. Richard will begin with some brief background material on the governing equations of subsurface reactive flows and on modern parallel computer architectures and programming models. RichardI will then discuss the software and algorithmic approaches that have enabled PFLOTRAN to provide scalable parallel performance on many thousands of processors. I will describe ongoing work to address disparate time and spatial scales by both the development of adaptive mesh refinement methods and the use of multiple continuum formulations. Finally, Richard will present some examples from recent simulations conducted on Jaguar, the 23412 processor core CrayXT3/4 system at Oak Ridge National Laboratory that is currently one of the top ten fastest supercomputers in the world.
Parallel and Scalable Finite Element/Volume Algorithms for CFD Applications
Shahrouz Aliabadi (Northrop Grumman Center for HPC - Jackson State University)
Thursday, February 21, 2008
Bldg. 5600, Room A-106
2:00 p.m.
Contact Sreekanth Pannala (574-3129) for more information.
Show/Hide Abstract
This presentation will be in three parts. In part (I), stabilized finite element and finite volume methods for fully incompressible and compressible flows will be introduced. The parallel scalability and vector computations of CaMEL flow solvers will be discussed. In part (II), a hybrid approach based on both finite element and finite volume methods for incompressible flows will be introduced.
The finite element applications will include the dispersion of contaminants in urban and battlefield environments, and free surface flows in hydrodynamics of ships in motion. The motion of the ships is accounted by coupling the nonlinear 6DOF rigid body dynamics with Navier–Stokes equations. The mesh-moving algorithms are based on linear and nonlinear elasticity equations. The sustained computational speed is measured more than one teraflop using unstructured meshes with two billion tetrahedral elements using Cray X1E with 256 processors. Many 3D numerical examples will be presented.
This presentation will report the performance of CaMEL_Aero, our truly matrix-free, parallel and vectorized unstructured finite volume solver for compressible flows. The Jacobian-free Generalized Minimal RESidual (GMRES) method is used to solve the nonlinear systems of equations using Newton-Raphson iterations. Furthermore, the matrix-free Lower-Upper Symmetric Gauss Seidel (LU-SGS) method is employed as a preconditioning technique to the GMRES solver. The aerodynamics calculation of complex 3D geometries will be discussed. This includes steady-state and transient aerodynamics calculations for Formula-1 racing cars as well as supersonic spinning projectiles.
In part (III), the development of an implicit hybrid (finite element and finite volume) flow solver for the incompressible Navier-Stokes equations will be introduced. The methodology is based on the pressure correction or projection method. A fractional step approach is used to obtain an intermediate velocity field by solving the original momentum equations with the matrix-free implicit cell-centered finite volume method. The Poisson equation derived from the fractional step approach is solved by the node-based Galerkin finite element method for an auxiliary variable. The auxiliary variable is closely related to the real pressure and is used to update the velocity field and the pressure field. We store the velocity components at cell centers and the auxiliary variable at cell vertices, making the current solver a staggered-mesh scheme. Several examples will be provided.
Mesh Adaptive Direct Search Algorithms for Constrained Mixed Variable Optimization
Lt. Col. Mark A. Abramson (Department of Mathematics and Statistics - Air Force Institute of Technology)
Thursday, February 21, 2008
Bldg. 5600, Room J-302
10:30 a.m.
Contact Ed D'Azevedo (576-7925) for more information.
Show/Hide Abstract
In this talk, we target a class of mixed variable
optimization problems in which the objective and constraint functions
may be nonsmooth, discontinuous, extended valued, computationally
expensive to evaluate, given as a black box, provide few significant
digits of accuracy, and may even fail to return a value. Furthermore,
constraint functions may return only a yes/no value, derivatives are
generally unavailable, and variables may be a mix of continuous,
integer, or nonnumeric categorical types (such as color, shape, or type
of material). Our approach for solving problems of this type is the
derivative-free class of mesh adaptive direct search algorithms. We
describe the details of this algorithm class, along with their
first-order and second-order theoretical convergence properties, and
then introduce some scientific and engineering applications for which
satisfying numerical results have been obtained.
Bubble Wrap For Bullets (and Bubbles): Draping of the Magnetic Fields of Galaxy Clusters
Jonathan Dursi (Canadian Institute for Theoretical Astrophysics, University of Toronto)
Monday, February 25, 2008
Bldg. 5600, Room J-302
10:30 a.m.
Contact Petr Plechac (241-5741) for more information.
Show/Hide Abstract
Clusters of galaxies are the largest bound objects in the Universe, and most of their normal matter exists in the form of extremely hot, diffuse, gas. High-resolution X-ray observations have revealed cavities with sharp edges in temperature, density, and metallicity in this gas; Their presence poses a puzzle since these features are not expected to be hydrodynamically stable, or to remain sharp in the presence of diffusion.
The mergers of galaxy clusters can be the most energetic events in the Universe, and even `minor' mergers are very dynamic events, which eventually lead to the stripping and dissolution of the smaller core.
Where this occurs is important -- it helps determine the thermal and compositional history of the evolution of the cluster (and thus its component galaxies).
With large 3D adaptive-mesh MHD simulations, and smaller more focused 2D simulations, we show how a moving core or bubble in even a very weakly magnetized plasma necessarily sweeps up enough magnetic field to build up a dynamically important sheath around the object; the layer's strength is set by a competition between `plowing up' of field and field lines slipping around the core, and to first order depends only on the ram pressure seen by the moving object.
Optimizing High Performance Communication Using NewMadeleine
Élisabeth Brunet (INRIA Runtime team of LaBRI, University of Bordeaux, France)
Thursday, February 28, 2008
Bldg. 5700, Room L-202
10:00 a.m.
Contact Cindy Sonewald (574-3125) for more information.
Show/Hide Abstract
Despite the spectacular progress made in high-performance communication interfaces, many potential optimizations are still unexplored. It is mainly
due to efforts in shortening the critical path to the maximum, in order to minimize latency. NewMadeleine is a communication library built around a powerful transfer optimizing engine with generic optimization strategies. These generic strategies are parametrized by the capacities of the target underlying network driver. By coordinating its own activity with that of the network cards, NewMadeleine has a global view of the application communication flows. Then, it becomes easy to multiplex them onto one or more physical network cards, even in cases of heterogeneous technologies. Moreover, the current trend in clusters leads towards an increase of the number of cores per node. In order to fully exploit them, NewMadeleine works in collaboration with PIOMan, the PM2 I/O Manager. PIOMan is a multithreaded communication engine able to exploit idle cores to speed up communications. We will thus see how this association takes advantage of all the available resources, whether in terms of computation or communication units, in order to improve the global application execution time.
Élisabeth Brunet, a PhD student, has been a member of the INRIA Runtime team of LaBRI (University of Bordeaux, France) since october 2005 (http://www.labri.fr/perso/brunet/). Her primary research interests are high-performance networking, generic communications algorithms for high-speed networks, and communication middleware programming. She is one of the principal designers of the NewMadeleine high-performance communication library.
|
|