Kevin, Adding on to what Fergal said..
Here is what we did. We started with a fixed number of columns and no topology. In this situation we picked the n% most innervated columns as the output of the SP. Thus we were guaranteed to get the correct sparsity of active columns. With this setup we did a lot of other tests to verify that the SP was forming good representations. The tricky part is if you want to do this with topology and local learning rules. Is that your concern? With topology we didn't try to guarantee the entire layer of cells will have exactly n% active columns. Exact numbers are not essential. We tried several different local learning rules, all of them produced about the right level of sparsity. We than ran the other tests to make sure that local learning rules didn't cause the SP to form poor representations. You won't get exactly the same results with topology and without topology but my recollection was we were able to come up with a set of local inhibition rules that produced good results. Jeff From: nupic [mailto:[email protected]] On Behalf Of Fergal Byrne Sent: Tuesday, February 04, 2014 10:43 AM To: NuPIC general mailing list. Subject: Re: [nupic-discuss] Tests for spatial pooling Hi Kevin, If you're using no topology (and no local inhibition) then the fraction of active columns (2% in NuPIC) is the only important factor. With topology, you should choose winners relative to their neighbours. In either case, the first test is to count the fraction of active columns. In the second case, measure the average distance between active columns. Regards, Fergal Byrne On Tue, Feb 4, 2014 at 6:05 PM, Kevin Martin <[email protected]> wrote: Hi, I'm writing my own version of the CLA. I have not reached anywhere significant and I have been playing with a very small number of columns until now. I am starting by implementing a spatial pooler and spatial pooling requires a large number of columns. So far it has been easy to manually check if the synapses are distributed throughout the input, if the winning columns are really sparse etc. But it is going to be impossible when, say,I use 1000 columns. Have somebody used a test to check if the spatial pooler outputs a sparse distribution? Any suggestions on how to write a test? Thanks, Kevin Martin Jose _______________________________________________ nupic mailing list [email protected] http://lists.numenta.org/mailman/listinfo/nupic_lists.numenta.org -- Fergal Byrne, Brenter IT http://inbits.com - Better Living through Thoughtful Technology e:[email protected] t:+353 83 4214179 Formerly of Adnet [email protected] http://www.adnet.ie <http://www.adnet.ie/>
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