But an upgrade gave it a score of 143.5 petaflops on the newest list. To match that speed, each person on the planet would have to perform 19 million calculations per second. Sierra got an upgrade, too, boosting its performance from 71.6 petaflops to 94.6 petaflops and lifting it from third place to second.

Summit and Sierra are siblings, each using IBM Power9 processors boosted by Nvidia Tesla V100 accelerator chips and connected with Mellanox high-speed Infiniband network connections. They're gargantuan machines made of row after row of refrigerator-size computing cabinets. Summit has 2.4 million processor cores and Sierra has 1.6 million.

Supercomputers are used for tasks like virtual testing of nuclear weapons, aerodynamic modeling of aircraft, understanding the formation of the universe, researching cancer and forecasting climate change effects. They're expensive but prestigious machines that can keep scientists and engineers at the vanguard of research.

The US once dominated the Top500 list, but China has steadily risen in clout. Its Sunway TaihuLight topped the Top500 for two years with a 93 petaflop score, and China extended its lead in the number of machines on the list.

A total of 227 of the Top500 machines are in China, compared with an all-time low of 109 for the US. The November list is the 52nd one released by a collection of academic researchers who compile it twice yearly for supercomputing conferences.

Linpack is only one speed test, though, and the Top500 has another designed to capture a broader range of performance abilities, the High-Performance Conjugate Gradient (HPCG) benchmark. On it, Summit and Sierra are head and shoulders above competing supercomputers.

Although Summit and Sierra use IBM's Power9 CPUs, the vast majority of Top500 machines use Intel processors. With the difficulties maintaining the performance increases described by Moore's Law, supercomputer makers have increasingly turned to various accelerator chips more specialized for mathematical calculations. Nvidia's chips, derived from its graphics processors, dominate this usage.

There is also a Chinese-speaking version with a different face.

Xinhua says the presenters can "work" 24 hours a day on its website and social media channels, "reducing news production costs".

The agency points out that they may be particularly useful for disseminating breaking news reports in a timely manner.

An artificial intelligence (AI) system has been used to synthesise the presenters' voices, lip movements and expressions. They are based on those of real Xinhua presenters.

This is different from using a 3D digital model of a human. It appears that photo-like facial features have been applied to a body template and animated.

The presenter struggled to appear completely natural, said Michael Wooldridge at the University of Oxford.

It was stuck somewhat in the "uncanny valley" - a term used to describe human-like robots and avatars which seem subtly unrealistic.

"It's quite difficult to watch for more than a few minutes. It's very flat, very single-paced, it's not got rhythm, pace or emphasis," Prof Wooldridge told the BBC.

He also pointed out that human news presenters have traditionally - in many cases - become highly trusted public figures.

"If you're just looking at animation you've completely lost that connection to an anchor," he added.

It was a "good first effort", however, said Noel Sharkey, emeritus professor of artificial intelligence and robotics at the University of Sheffield.

"We will see it improve over time," he told the BBC. "The problem is that it could be very dull."