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Peter Clarke
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Re: Image decompression
Peter Clarke   7/16/2013 3:50:38 AM
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I meant the toughest (highest resolution) application requirement.

Power is always a key parameter in mobile but to-date nobody has thought it worrth using 8-bit or 4-bit ALUs for some "application" calculations.

And there is an issue in some apps of handling rounding errors to prevent them building up.

 

tb100
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CEO
Re: Image decompression
tb100   7/15/2013 12:20:01 PM
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"the block tends to be specified for the toughest requirement and then operated at that level."

 

I can understand that, but in cell phones the toughest requirement is usually power. I don't know the impact of inexact caclucations on video quality, but I'm willing to bet that a 90% power reduction would trumpt exact calculations in many cases.

Peter Clarke
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Re: Architectural options
Peter Clarke   7/15/2013 4:15:53 AM
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I agree that three identical low resolution data engines running the same software would tend to produce identical inexact results making a voting regime redundant. Nonetheless I think there is scope for more creative thinking here.

How about this?

Three (or more) low-resolution data engines running different algorithmic approaches to achieve the same functionality might produce different inexact results that could be averaged to produce a higher resolution final result, but with a significant reduction in energy consumption.

 

 

Peter Clarke
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Re: Image decompression
Peter Clarke   7/15/2013 4:09:56 AM
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They do indeed put compression/decompression engines in graphics processors.

In fact some systems have ways to offload compression/decompression to the GPU in a heterogeneous processor system.


But as with examples given above the accuracy, loss/losslessness required may depend on application (video versus communications) and as such the block tends to be specified for the toughest requirement and then operated at that level.

rbv
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Freelancer
Re: Architectural options
rbv   7/10/2013 1:53:18 PM
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Voting assumes that the error distribution is independent of the data, but it almost certainly isn't.  Three identical processors may give three results with identical errors.

An average error magnitude estimate also isn't very meaningful. What fraction of inputs produces results 2% in error or more?

tb100
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CEO
Image decompression
tb100   7/9/2013 8:33:46 PM
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Don't they put video decompression engines in processors/video chips nowdays to help with handling MPEG video streams? This seems like the perfect application for inexact calculation.

Also, VoLTE is the up-and-coming voice standard for phones that all the major cell companies are headed toward. This is another application that uses a reasonable amount of CPU power where inexact processing would work and the power savings would be very desireable.

LarryM99
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CEO
Architectural options
LarryM99   7/8/2013 7:07:13 PM
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If the power savings were 50% or less I would say that it wasn't very interesting, but at 90% you have the option of running multiple cores on the same data and voting for the correct answer. Three cores with only a .25% variance should be pretty close to reliable, depending on the distribution of the errors. Granted, it would "only" save 70% of the power, but would definitely be worth exploring.

It is also worth looking at where the errors show up. If programmatic logic is not affected, then network routers and many control systems would definitely benefit. I would expect that data collection systems that do advanced math would be leery of it unless the error range could be bounded and manageable.



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