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TechNewsWorld.com

New Chip Startup Plays the Odds on Probability Processing

By Richard Adhikari
Aug 18, 2010 5:00 AM PT

Lyric Semiconductor, a spinout from the Massachusetts Institute of Technology, announced on Tuesday a new approach to a technology called "probability processing."

New Chip Startup Plays the Odds on Probability Processing

Probability processing uses probability bits, which calculate the probability of an event happening. This technology required the company to redesign processors to natively process probabilities from the ground up and to write a new programming language to express probabilities.

Sampling of Lyric's general-purpose programmable probability processing platform is scheduled for 2013.

Six Impossible Things Before Breakfast

Conventional processors are based on Boolean logic, whose bits have only two possible values. These are represented in various ways, one being "on" and "off." In data processing, these values are zeroes and ones. Boolean logic gates perform operations on these bits sequentially.

However, this sequential processing is sometimes imperfectly suited for applications such as search, fraud detection, spam filtering, financial modeling and genome sequence analysis, which require simultaneously considering several possibilities and deciding on the best answer.

That's where probability processing shines, Ben Vigoda, Lyric Semiconductor's CEO, told TechNewsWorld. It's based on Pbits, or probability bits.

"Digital bits flow through Boolean logic gates, while Pbits flow through probability or Bayesian gates multi-directionally," Vigoda said. "While digital processors program each operation in sequence, probability processors allow all the variables to talk to each other."

A Pbit is the probability of a bit. Every event has two possibilities -- it either happens or does not happen -- and a Pbit encapsulates that, Vigoda said.

By letting all the variables talk to each other simultaneously, probability processors engage in both multidimensional and parallel processing, Vigoda pointed out.

"It's a parallel processor where a lot of things talk to a lot of other things in a high dimension. Think of it as hypercube routing," he said.

This may result in 1,000-fold improvement in power, storage and cost expenditures for applications that are suited to probability processing, Lyric believes.

Calculating Probability

Lyric needed to redesign gates so they could take in inputs between zero and one and put out the result in order to achieve digital processing. Boolean gates deal with inputs of either zero or one.

Probability processing uses Bayesian probability. To calculate the probability of an event, you have to specify a prior probability, then update it when new data comes in. The Bayesian interpretation provides a standard set of procedures and formulae to perform this calculation.

There are two views on Bayesian probability. One is the objectivist view, which holds that the rules of Bayesian statistics can be justified by requirements of rationality and consistency and interpreted as an extension of logic. The other is the subjectivist view, which considers the state of knowledge as measuring a personal belief.

Like many modern machine learning methods, Lyric uses Bayesian objectivist principles.

Error Correction

As its first product, Lyric is offering Lyric Error Correction for flash memory, or LEC. This is an advanced error corrector for flash memories that's 30 times smaller than standard products, and has 12 times lower power consumption.

The LEC will eventually be put onto the NAND flash chip itself, Vigoda said. That's called "EZ NAND."

"The whole industry wants to go to EZ NAND but the error corrector is big and uses a lot of area," Vigoda said. "Because ours is so much smaller, it helps EZ NAND along."

Currently, one in every thousand bits stored in flash memory comes out wrong, and Lyric predicts the ration will be close to one in every hundred in the next generation of flash memory. The problem is that flash errors increase as manufacturers increase the density of flash.

The host controller must handle all error correction, and that slows down NAND flash. The problem's significant enough that the Open NAND Flash Interface (ONFI) Working Group, an industry group led by Micron Technologies, is working on new error correction code (ECC) specs.

The specs should be completed by the end of the month, Kevin Kilbuck, chairman of the ONFI Marketing Committee and director of strategic NAND marketing at Micron, told TechNewsWorld.

Lyric's LEC technology is available for license now.

Lyric's Probability Processor

Lyric is also working on the GP5 -- a general-purpose programmable probability processing platform.

This will calculate probabilities for all types of applications and could enable performance gains of 1,000 times over x-86-based processors.

It will run code written in Lyric's own probability programming language, Probability Synthesizes to Bayesian Logic (PSBL).

The GP5 will be targeted at applications that use a lot of Bayesian calculations, such as trading companies.

"Our plan is to identify applications where there's a recognized need to compute probabilities and deliver packaged solutions for them," Mira Wilczek, Lyric's director of business development, told TechNewsWorld.

The GP5 is scheduled to begin sampling in 2013.


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