TOKYO -- China has jumped to the front ranks of the supercomputing powers, with its Sunway TaihuLight, powered by domestically developed chips, recently recognized as the fastest computer in the world.

In its debut on the Top500 list of the world's fastest supercomputers in June, the Sunway TaihuLight overwhelmed such rivals as the Tianhe-2, a Chinese supercomputer powered by Intel chips that has claimed the No. 1 spot on the past six Top500 lists. Furthermore, it was the first time for China to surpass the U.S. in the total number of systems on the list.

The Top500 list is published twice a year, in June and November. In 2011, Japan's K computer, developed by the Riken Advanced Institute for Computational Science, was ranked first in two consecutive editions of the list.

The following year, however, the K was dethroned, outperformed by the U.S.-made machines Titan and Sequoia.

In 2013, China's Tianhe-2 took the title and maintained the No. 1 position for six straight releases of the Top500 list.

U.S. export ban

The Tianhe-2's use of Intel processors became an international issue in February last year, when the U.S. government, claiming that China was using the computer to develop nuclear weapons, banned U.S. companies from exporting microprocessors and other supercomputer parts to the country.

But China's National Research Center of Parallel Computer Engineering and Technology was already developing a newer computing monster using processors designed and made in China.

The Sunway TaihuLight claimed the top slot on the latest edition of the Top500 list, which ranks supercomputers in terms of calculation speed. No other supercomputer came close to China's new system, whose theoretical peak performance is 93 petaflops -- meaning it can perform 1 quadrillion calculations per second.

The Chinese computer also took the third spot on the Green500 list, which ranks the 500 fastest supercomputers by energy efficiency, or calculation speed per watt.

The two Riken systems were ranked No. 1 and No. 2 on this list in June, but they are specialized systems designed for energy-efficient calculations. In other words, the Sunway TaihuLight is the greenest supercomputer among purely high-speed systems.

China was able to create a machine that is both powerful and energy efficient by using an enormous number of processors through advanced parallel computing technology while restricting the performance of energy-hogging memory devices. Since the Top500 rankings are based on the speed of simple calculations, memory performance is not a critical factor.

For actual scientific computing, which involves more complicated calculations, memory performance is more crucial to the system's overall number-crunching power.

Impressively, the Sunway TaihuLight also ranked second on the Graph500 list, which ranks supercomputers by their ability to handle data-intensive applications, such as big data analysis.

The Chinese system is probably designed so that its precise optimization of the recording and calling of data, as well as its intrasystem communications, make up for the relatively low performance of its memories. Satoshi Matsuoka, a professor at the Tokyo Institute of Technology, called it an "amazing" achievement.

The Chinese supercomputer also took the third spot in the High Performance Conjugate Gradient (HPCG) category, a computing metric that focuses on the ability to deal with complicated engineering problems.

The Sunway TaihuLight is already being used for such gargantuan number-crunching tasks as meteorological simulations. It is one of the finalists for this year's Gordon Bell Prize, which recognizes outstanding achievements in high-performance computing.

The latest edition of the Top500 supercomputer rankings highlights China's rapid advance in this field. The number of Chinese systems on the list was larger than that of U.S. competitors for the first time, albeit by a narrow margin.

Japan's K supercomputer at Riken

Japan aims for balance

China's ascent to the status of computing superpower has changed the landscape in this technological race. Some experts say China has already caught up with, or even overtaken, the U.S. and Japan in this field.

"China has a good chance of becoming an exporter of processors," Matsuoka said.

Japan's K computer, meanwhile, has been gradually falling in the rankings, ending up in the fifth position with the latest Top500 list.

Still, the Riken system maintained its top spot on the Graph500 list for the third consecutive time and ranked second in the HPCG category, above the Sunway TaihuLight. Behind that outcome are the different design philosophies of the K and Chinese computers.

In stark contrast with the Sunway TaihuLight, the K is powered by high-performance memories so that it can cope with a wide range of actual supercomputing tasks.

While its speed -- as measured by the benchmark used for the Top500 list -- is only one-ninth that of the Chinese system, the K can carry out more complicated tasks without slowing much.