Obama orders world's fastest computer

The supercomputer would be 20 times quicker than the current leading machine, which is in China.
It would be capable of making one quintillion (a billion billion) calculations per second, a figure which is known as one exaflop. A body called the National Strategic Computing Initiative (NSCI) will be set up to research and build the computer.
The US is seeking the new supercomputer, significantly faster than today's models, to perform complex simulations, aid scientific research and national security projects.
It is hoped the machine would help to analyse weather data for more accurate forecasts or assist in cancer diagnoses by analysing X-ray images.
Richard Kenway at the University of Edinburgh says he thinks the plan is "spot on" in terms of strategy, bringing together both the ambition to develop new hardware and also improved analysis of big data.
He explained the computer could aid the development of personalised medicines, tailored to specific individuals.
"Today, drugs are designed for the average human and they work OK for some people but not others," he told the BBC.
"The real challenge in precision medicine is to move from designing average drugs to designing drugs for the individual because you can know their genome and their lifestyle."