Hi, Fergal is correct. “Reconstruction” was the first approach we used to take the state of the CLA’s predicted cells and turn it into a value that can be used outside of the CLA. It worked fine. The problem we had was customers often didn’t want to know the prediction for the next data point. They wanted a prediction for say one hour in advance, or every hour for twenty four hours. Reconstruction didn’t suffice. The solution was to implement a separate classifier. We stored the state of the CLA in a buffer and when the appropriate input actually arrived (say one hour hence) we could pair the earlier state of the CLA with the correct input. The classifier doesn’t need to know what cells are in the predicted state only what cells are active. We had some options on how the implement the classifier. I believe what we implemented was we kept a histogram of input values for each cell. When a cell became active we updated the histogram. To make a prediction we combined the histogram of all the currently active cells. This worked well. A better prediction could be created if we kept a histogram for each active dendrite segment instead of each active cell. This would take more memory and more training data so we didn’t pursue it.
If a customer wanted to make a prediction one hour and two hours in advance we would implement two classifiers. Jeff From: nupic [mailto:[email protected]] On Behalf Of Fergal Byrne Sent: Saturday, October 19, 2013 3:35 AM To: NuPIC general mailing list. Subject: Re: [nupic-dev] Regarding CLA Hi Aseem, The grannies idea came from the go-back to the bits idea, which I believe the Numenta guys call "reconstruction". That strategy did not use cells and reverse dendrites, but a procedural equivalent. They'll tell you why this was abandoned in favour of the lookup tables for Grok. Regards, Fergal Byrne — Sent from Mailbox <https://www.dropbox.com/mailbox> for iPhone On Sat, Oct 19, 2013 at 8:52 AM, Aseem Hegshetye <[email protected]> wrote: Hi, This was one of the awesomest replies i have got on this emailing list. Grannies idea looks great. we should try simulating it Fergal. Even I thought of something that would replace those look up tables. When we have cells in predictive state, its like predicting that the input bits are going to fire that column. So if we go reverse and check that columns weight to all 121 input bits we can infer the next input. Plus we have 40 different columns in predictive state, whose weights with input patterns add up to give a descent prediction. I dont know if its already been tried , but if not I am curious to try, and i have already started simulations. Also Grannies idea needs to be tried. regards Aseem Hegshetye _______________________________________________ nupic mailing list [email protected] http://lists.numenta.org/mailman/listinfo/nupic_lists.numenta.org
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