Close. Using your "scale" analogy...
Resolution = unit of measure of the most granular increment of change. (i.e .01g) Capacity = count of distinct inputs possible at said resolution (i.e if scale range is 0 to 10, then 1000) Accuracy = how "well" does the scale perform it's task of measuring weight (i.e how often is it correct?) I don't know if resolution can be measured with the spacial pooler? David Sent from my iPhone > On Jul 11, 2014, at 6:48 AM, Rik <[email protected]> wrote: > >>> Sorry what value can be 1 billion? You keep bringing up that number. No >>> spatial pooler of any sane dimensions has a capacity of 1 billion. Not for >>> any reasonable definition of "capacity". >> >> In this case we are just trying to discriminate between a fixed set of >> patterns. By "discriminate" we mean the SDR output should be unique with >> respect to the other patterns by at least one winning column. Since there >> are 1024 columns, of which 64 are on at a time, the total number of patterns >> that can be discriminated is 1024 choose 64 > 10^102. In reality it will be >> less than that, but if two inputs differ by more than a few bits, we will >> have at least one column that is different. As such, there is quite a bit of >> room here. > The SP output can possibly produce 1 billion+ different patterns but that is > what I would consider its "resolution", not its "capacity" or "accuracy" > which is what we're after in this thread and what is the desirable property > that one seeks to evaluate and optimize. A completely unlearned SP will also > produce 1 billion+ different output patterns so that can't possibly be an > interesting property. > > A real-world analogy: The local jeweler weighs precious metals with > scales boasting a resolution of .01g but in the interest of getting a fair > deal on my silver I'd rather know their accuracy. Scales with a resolution of > .01g can still be off by 5g and usually will be so straight off the assembly > line so they have to be calibrated, a primitive material world version of > "learning". > > Or your digital SLR camera + computer monitor boast a 24bit color depth > allowing for 4 million+ colors but that's saying nothing about how faithfully > they reproduce the exact shade of red of a flower that you photographed and > there's a calibration/"learning" process too that involves photographing > known colors off a pantone sheet. > > A good definition of SP capacity or accuracy would IMHO involve a correlation > between inputs and ouputs, along the lines of how well clusters in the input > vector space correlate to clusters in the output vector space. Just thinking > out loud here. > > -- Rik > > _______________________________________________ > nupic mailing list > [email protected] > http://lists.numenta.org/mailman/listinfo/nupic_lists.numenta.org
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