The Department of Energy's Oak Ridge National Laboratory is again home to the most powerful computer in the world, according to the Top500 list, a semiannual ranking of computing systems around the world. The list was announced at this week's SC12 International Conference for High Performance Computing, Networking, Storage and Analysis in Salt Lake City, Utah.

Titan replaced the XT5 Jaguar at ORNL last month. Jaguar ranked as the world's fastest computer on the Top500 lists in November 2009 and June 2010, and now Titan is the scientific research community's most powerful computational tool for exploring solutions to some of today's most challenging problems.

"The new Top500 list clearly demonstrates the U.S. commitment to applying high-performance computing to breakthrough science, and that's our focus at Oak Ridge," said ORNL Director Thom Mason. "We'll deliver science from Day One with Titan, and I look forward to the advancements the Titan team will make in areas such as materials research, nuclear energy, combustion and climate science."

Titan is a Cray XK7 system that contains 18,688 nodes, each built from a 16-core AMD Opteron 6274 processor and an NVIDIA Tesla K20X GPU accelerator. Titan also has 710 terabytes of memory.

Its hybrid architecture - the combination of traditional central processing units (CPUs) with graphic processing units (GPUs) - is largely lauded as the first step toward the goal of exascale computing, or generating 1,000 quadrillion calculations per second using 20 megawatts of electricity or less.

Titan reached a speed of 17.59 petaflops on the Linpack benchmark test - the specific application that is used to rank supercomputers on the Top500 list. Titan is capable of a theoretical peak speed of 27 quadrillion calculations per second - 27 petaflops - while using approximately 9 megawatts of electricity, roughly the amount required for 9,000 homes.

That capability makes Titan 10 times faster than Jaguar with only a 20 percent increase in electrical power consumption - a major efficiency coup made possible by GPUs, which were first created for computer gaming.

"It's not practical or affordable to continue increasing supercomputing capacity with traditional CPU-only architecture," said ORNL's Jeff Nichols, associate laboratory director for computing and computational sciences. "Combining GPUs and CPUs is a responsible move toward lowering our carbon footprint, and Titan will enable scientific leadership by providing unprecedented computing power for research in energy, climate change, materials, and other disciplines."

Because they handle hundreds of calculations simultaneously, GPUs can perform many more calculations than CPUs in a given time. By relying on its 299,008 CPU cores to guide simulations and allowing its new NVIDIA GPUs to do the heavy lifting, Titan will enable researchers to run scientific calculations with greater speed and increased fidelity.

"The order of magnitude performance increase of Titan over Jaguar will allow U.S. scientists and industry to address problems they could only dream of tackling before," said Buddy Bland, Titan project manager at DOE's Oak Ridge Leadership Computing Facility. Scientists began using portions of Titan as it was under construction, demonstrating the significant capabilities of the hybrid system. Among early application areas:

* Materials research: The magnetic properties of materials could vastly accelerate numerous technologies such as next-generation electric motors and generators, and Titan already is allowing researchers to improve the calculations of a material's magnetic states as they vary by temperature.
* Fuel combustion: Because three-quarters of fossil fuels burned in America power cars and trucks, improving the efficiency of internal combustion engines is critical. Researchers will use Titan's unprecedented power to model combustion of large-molecule hydrocarbon fuels such as the isooctane (an important component of gasoline), commercially important oxygenated alcohols such as ethanol and butanol, and biofuel surrogates.
* Nuclear power: The U.S. acquires 20 percent of its power from nuclear plants, and Titan will lead the way to extending the life cycles of aging reactors and ensuring they remain safe. Titan allows researchers to simulate a fuel rod through one round of use in a reactor core in 13 hours, a job that took 60 hours on the Jaguar system.

Other efforts include calculating specific climate change adaptation and mitigation scenarios, obtaining a molecular description of thin films important for the emerging field of flexible organic electronic devices, and calculating radiation transport, a process important in fields ranging from astrophysics to medical imaging.

"Titan builds on the Oak Ridge Leadership Computing Facility's established reputation for enabling transformational discoveries across the scientific spectrum," Nichols said.

ORNL is managed by UT-Battelle for the Department of Energy. The Department of Energy is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time.

The Oak Ridge Leadership Computing Facility supports national science priorities through deployment and operation of advanced supercomputers as part of DOE's commitment to providing scientists with world-leading research tools.

The Top500 project was started in 1993 to provide a basis for tracking and detecting trends in high-performance computing. Twice a year, a list of sites operating the 500 most powerful computer systems is released. The best performance on the High Performance Linpack benchmark is used as performance measure for ranking the computer systems. The list contains a variety of information including the system's specifications and its major application areas.