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Winter/Spring 1997

NCAR provides new computing capacity for research

by Brian Bevirt
NCAR Scientific Computing Division

With the recent installation of two new supercomputers--a Cray C90 and a Cray J90se--the computing systems in NCAR's supercomputing center are sustaining about ten billion floating-point operations per second (10 GFLOPS) as they run models that simulate atmospheric, oceanic, and other geophysical processes. This is more than 100 times the computing power that NCAR provided to researchers just 12 years ago.

The C-90's arrival at NCAR. (Photo by Carlye Calvin.)

Back then, NCAR's Scientific Computing Division (SCD) operated two Cray 1-A computers--that era's state of the art in supercomputing. Today, SCD operates seven Cray computers that average about 80 times the productivity of a Cray Y-MP processor (a standard SCD uses to compare computer performance). These supercomputers are divided into two groups: community computing and dedicated climate simulation.

The long road to acquiring new computing power

By last October, projects using the Climate Simulation Laboratory (CSL), such as the NCAR Coupled Climate Model Project, needed a machine that could sustain at least 5 GFLOPS. Also, by October 1998, CSL users will need at least one machine that can sustain approximately 20 GFLOPS to decrease the completion time of centuries-long climate simulations, incorporate more physical processes into the models, and eventually increase the models' spatial resolution.

In 1995, NCAR initiated a procurement effort to fulfill the needs of the Climate Simulation Laboratory and upgrade community computing power. In the spring of 1996, after extensive performance testing of the computing systems that qualified under the procurement's request for proposals, UCAR announced that equipment from NEC was selected. Of the machines that NCAR has tested, the NEC SX-4 is the only machine that has demonstrated the ability to sustain approximately 20 GFLOPS on the class of simulations that will be addressed by CSL models in 1998 and beyond.

However, acquisition of an SX-4 has been delayed due to a series of dumping claims and counterclaims addressing whether the NEC system was being offered to NCAR at an unfairly low price. Investigations are under way at both the U.S. International Trade Commission and the Court of International Trade, and the situation is not expected to be resolved until well into 1997. Consequently, in the fall of 1996, NCAR upgraded the Cray Y-MP in the CSL to a Cray C90. The C90 provides the 5 GFLOPS capability needed by the CSL models this year.

SCD's fiscal year 1997 budget includes over $1 million of funding for an upgrade to community resources. SCD discussed several options with its advisory panel for using that funding to provide community users with an interim upgrade. The panel recommended acquiring a Cray J90se with 20 processors and one billion words of memory.

A look at the CSL computers

The CSL computers support a small number of activities that need large amounts of computing, such as coupled climate system models. The laboratory is a multiagency entity supported by the U.S. Global Change Research Program. The CSL completed its first year of operation on 31 July 1996, and during this year nearly 100,000 equivalent Y-MP hours were delivered to 11 projects selected by the CSL Allocations Panel. The projects used this computer time to carry out multidecadal simulations and to develop and evaluate components for use in coupled systems models.

The new Cray C90, named antero, is dedicated to the CSL. This system replaces one of NCAR's Cray Y-MPs that was also named antero. The new antero arrived at NCAR during November 1996 and went into production a few weeks later. It provides better than a factor of four increase in computing power over the former antero.

"On the new antero, the Climate System Model is simulating five years per day of wall-clock time instead of one year per day on the former antero," notes NCAR researcher Byron Boville (Climate and Global Dynamics Division). The Climate System Model calculates physical processes in the atmosphere, ocean, land, and sea ice to simulate the evolution of climate.

The four CSL computers together provide about 7 GFLOPS of sustained computing power.

Community computing equipment

The community computing resources provide reliable, general-purpose computing power to a wide range of users in the areas of

NCAR's other new supercomputer, a Cray J90se named ouray, provides the large memory needed by many models. This feature allows community computing users to run much larger jobs than they could on the other resources. The complete set of community computers provides about 3 GFLOPS of sustained computing power.

For more information

There is a lot more to NCAR's computing facility than the computing engines. Other major components include a mass storage system, local and wide area networks, distributed computing services, and visualization laboratories. SCD provides a wealth of information about the NCAR supercomputing center via the World Wide Web. Starting at SCD's home page, you can find information about the supercomputers, SCD's services for users, NCAR's data archive and mathematical and statistical libraries, and the visualization labs. SCDzine, is a Web-based magazine about NCAR computing resources for the international geosciences community. For information about NCAR Graphics scientific visualization software, visit the NCAR Graphics Home Page.

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Edited by Carol Rasmussen, carolr@ucar.edu
Prepared for the Web by Jacque Marshall
Last revised: Tue Apr 4 13:38:24 MDT 2000