Grids and Worldwide
Computing
Members of Rensselaer’s Center for Pervasive Computing and Networking are
involved in research projects to overcome many of the challenges that stand
in the way of worldwide computing. In this vision, local computers – and
even various mobile devices such as cameras, credit cards, or
computer-enabled watches, rings and eyeglasses – come together to form a
virtual organization. Such an organization could use the shared computing
resources to form a “grid,” a virtual supercomputer that tackles difficult
scientific problems. Or a virtual organization could bring together all
parties to a transaction such as a house purchase, including real estate
agents, lawyers, banks, a title search firm, insurance companies, mortgage
brokers and issuing agencies, inspectors, taxing jurisdictions, and the
title records office to complete a transaction entirely on-line. Although
grid computing made a lot of progress in the recent years through projects
such as Globus, the focus in Rensselaer’s Center is on more dynamic and
autonomous environments in which the task allocation, migration, and fault
tolerance are automatically supported.
Middleware Software
for Grids
High-performance computing once relied almost exclusively on supercomputers
and massively parallel machines. The increasing power of PCs and
workstations, however, has made it possible to use clusters of these
machines for parallel computing. Even more complex is metacomputing, the
effort to connect hundreds, thousands, or even millions of computers through
the Web to tackle problems of universal interest. One difficulty is ensuring
efficient and fast access to a huge and widely distributed database.
Boleslaw Szymanski, professor of
computer science and founding director of Rensselaer’s Center for Pervasive
Computing and Networking, and his colleagues are developing high-level
services and protocols that significantly boost the performance of grid
computing. Their replication management protocols offer high data
availability, low bandwidth consumption, increased fault tolerance, and
improved scalability. Dr. Szymanski collaborates with the GLOBUS Group to
integrate his tools into the GLOBUS system for grid computing. He also works
with IBM-Almaden, using this group’s Smart-Grid system as a test bed for his
research. In a project designed to show the power of metacomputing, Dr.
Szymanski and others at Rensselaer linked hundreds of heterogeneous
computers to study twin primes, pairs of prime numbers that differ by only
two, such as 3 and 5 or 11 and 13. They counted the number of twin primes,
computed the sum of their inverses, and found the maximum distance between
twins and the locations of the gaps for a range of numbers two orders of
magnitude larger than the previous record-breaking effort. Using idle time
on the processors of those who had volunteered to participate, they
completed the calculation in two years rather than the 100 years it would
have taken on a single workstation.
Programming Models and
Tools for Dynamic Grids
Carlos Varela, assistant
professor of computer science at Rensselaer, is developing programming
models, languages, and tools for worldwide computing. For many of the
applications now envisioned, a system is needed that can evenly distribute
workloads and redistribute them as conditions change or devices move, that
allows nodes randomly to come on and off line, that helps the server
reconfigure itself as it is accessed by a range of devices, and that can run
without interruption as the basic topology of the network evolves. In
collaboration with Dr. Gul Agha at the University of Illinois at
Urbana-Champaign, Dr. Varela uses the actor model, which provides a unit of
abstraction for concurrency and mobility. Dr. Varela and his colleagues have
developed SALSA (Simple Actor Language, System, and Architecture), an actor
programming language, to support the specialized needs of mobile computing.
In a collaboration with IBM, Dr. Varela is developing a transactor model for
reliable Web computing, a model specifically designed to support e-business
by building reliability into a system that may contain unreliable nodes or
links. In other work supported by IBM, Dr. Varela is using the Eclipse open
source code as a tool to help visualize and graphically represent
distributed computations. Drs. Varela, Joseph Flaherty, and Szymanski are
also working with a group of physicists and biologists to use a worldwide
computing approach for two scientific computation applications – the search
for missing baryons (sub-atomic particles that have not been observed) and a
study of the mechanisms by which bacteria evolve.
Scalable Routing in
Unreliable Grids
Alhussein Abouzeid, assistant
professor of electrical, computer, and systems engineering at Rensselaer, is
investigating methods of routing messages on the unreliable networks formed
in grid computing. In such cases, it is necessary to find nodes where
computing resources are available, to allocate jobs to resources in ways
that maximize performance, and to find new routes when nodes become
unavailable. One must do all of this while expending a minimum amount of
overhead, defined as computing time and power, and the system must be
scalable to infinitely large systems without deteriorating quality. Dr.
Abouzeid analyzes the changes of topology as a random process, and applies
information-theoretic principles to quantify the minimum amount of overhead
(bits/sec). He introduced the principle of “statistical traffic
localization” that governs the selection of interacting peers in a dynamic
grid. He has shown that grids that are designed according to this principle
are infinitely scalable to arbitrary large numbers while keeping the
overhead bounded.
Virtual Embedding for
World Wide Computing
Bulent Yener, associate professor of computer science,
suggests bridging the gap between supercomputing and grid computing by
creating a virtual mesh and embedding it on top of the arbitrary mesh formed
by the heterogeneous group of computers used in grid computing. The goal is
to embed a virtual supercomputer architecture with minimum interference. In
a dynamic wireless network, for example, routing information is obtained for
the mobile terminals and mobile base stations, and this information is
partitioned into a hierarchical, distributed database, based on the virtual
topology. He has shown that such a system can cope with a high degree of
mobility in the system and still successfully deliver packets to their
destinations.
Concept-Based Software
for Embedded Systems
David Musser, professor of
computer science, is one of the originators of the concept-based approach
that has led to widely used generic software libraries for data processing,
scientific computation, and graph computation, including the Standard
Template Library, the Matrix Template Library, and the Boost Graph Library.
He is extending these methods to produce generic libraries and high-level
optimization for embedded computing systems. In the concept-based approach,
software artifacts are systematically classified according to their formal
requirements. Concept refinement uncovers basic relationships and makes it
possible to develop generic components that produce optimal program designs.
Dr. Musser proposes using traditional concepts such as Algorithm, Iterator,
Functor, Adaptor, and Allocator. In collaboration with Drs. Luk and
Szymanski, he is also developing new concepts, such as distribution
coordinators and mobility negotiators, that are needed for distributed
real-time and embedded computing. His strategy is to begin with real
problems being tackled in the Center for Pervasive Computing and Networking
and work upward toward generalized concepts.
Parallel Processing
Algorithms for Eye Surgery
Rensselaer researchers are using high-speed parallel processing algorithms
to develop an improved system for laser surgery on the retina. Their system
gives surgeons real-time information to better aim the laser. Surgeons now
must look at a small section of the eye and coordinate it with another map
of the whole eye, a task so difficult that there is a 50 percent error rate.
Chris Carothers, assistant
professor of computer science, and collaborators have developed algorithms
that take advantage the 4 MB pages provided by an Intel processor to
continuously in real-time map blood vessels, locate landmarks, and
coordinate images, keeping track of the laser’s position despite the
unpredictable, random movements of the human eye during surgery.
Contacts: