Circuit design is usually no place for mistakes. But new research shows that introducing a controlled quantity of errors into a simple circuit can double its speed while also halving its energy consumption and size.

The researchers behind the work are using the design method to create hearing aids that they hope will have much longer battery lives. The methods could also improve the efficiency of other specialized circuits used in displays and cameras.

Researchers led by Krishna Palem, a professor of computing at Rice University, have designed an algorithm that modifies a circuit's design to make it more efficient, given a set rate of errors that can be tolerated. Researchers from Palem's lab presented the work last week at the DATE11 conference in Grenoble, France.

Allowing for a predetermined rate of errors can lead to major efficiency gains without a noticeable drop in performance. As long as the errors are introduced in a controlled way, and the most important parts of an operation are protected from error, small errors are tolerable in many applications—for example, in audio and graphical signal processing. A single such computational mistake might result in a tiny, momentary distortion in an image or sound that most people would not be able to detect.

Lowering the voltage a circuit uses in order to decrease power consumption will introduce errors. When the voltage is lower, some parts of a circuit run slower than the rest, leading to mistakes. Computer scientists have made chips that vary the voltage of different parts of the circuit on the fly. But these designs are complex and increase the size of a chip.

"You can think of a circuit like a network of roads," says Palem. As information flows through a circuit, some paths have heavy traffic, some hardly any. The Rice group's algorithm analyzes a circuit to identify paths that can be "pruned," while only introducing tolerable errors. "We ran audio files through the circuit, and looked for zones of high, medium, and low activity over a series of diagnostic trials," explains Palem.