by Staff Writers
Boston MA (SPX) Oct 31, 2014
As transistors get smaller, they also grow less reliable. Increasing their operating voltage can help, but that means a corresponding increase in power consumption.
With information technology consuming a steadily growing fraction of the world's energy supplies, some researchers and hardware manufacturers are exploring the possibility of simply letting chips botch the occasional computation. In many popular applications - video rendering, for instance - users probably wouldn't notice the difference, and it could significantly improve energy efficiency.
At this year's Object-Oriented Programming, Systems, Languages and Applications (OOPSLA) conference, researchers from MIT's Computer Science and Artificial Intelligence Laboratory presented a new system that lets programmers identify sections of their code that can tolerate a little error.
The system then determines which program instructions to assign to unreliable hardware components, to maximize energy savings while still meeting the programmers' accuracy requirements.
The system, dubbed Chisel, also features a tool that helps programmers evaluate precisely how much error their programs can tolerate.
If 1 percent of the pixels in an image are improperly rendered, will the user notice? How about 2 percent, or 5 percent? Chisel will simulate the execution of the image-rendering algorithm on unreliable hardware as many times as the programmer requests, with as many different error rates. That takes the guesswork out determining accuracy requirements.
The researchers tested their system on a handful of common image-processing and financial-analysis algorithms, using a range of unreliable-hardware models culled from the research literature. In simulations, the resulting power savings ranged from 9 to 19 percent.
Rely provides the mechanism for specifying the accuracy requirements, and it features an operator - a period, or dot - that indicates that a particular instruction may be executed on unreliable hardware. In the work presented last year, programmers had to insert the dots by hand. Chisel does the insertion automatically - and guarantees that its assignment will maximize energy savings.
"One of the observations from all of our previous research was that usually, the computations we analyzed spent most of their time on one or several functions that were really computationally intensive," says Sasa Misailovic, a graduate student in electrical engineering and computer science and lead author on the new paper.
"We call those computations 'kernels,' and we focused on them."
Misailovic is joined on the paper by his advisor, Martin Rinard, a professor in the Department of Electrical Engineering and Computer Science (EECS); by Sara Achour and Zichao Qi, who are also students in Rinard's group; and by Michael Carbin, who did his PhD with Rinard and will join the EECS faculty next year.
In practice, Misailovic says, programs generally have only a few kernels. In principle, Chisel could have been designed to find them automatically. But most developers who work on high-performance code will probably want to maintain a degree of control over what their programs are doing, Rinard says. And generally, they already use tools that make kernel identification easy.
But the researchers developed three separate mathematical expressions that describe accuracy of computation, reliability of instruction execution, and energy savings as functions of the individual instructions.
These expressions constrain the search that the system has to perform to determine which instructions to assign to unreliable hardware. That simpler - though still complex - problem is one that off-the-shelf software can handle.
Massachusetts Institute of Technology
Computer Chip Architecture, Technology and Manufacture
Nano Technology News From SpaceMart.com
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|