On Mon, Jan 23, 2017 at 7:59 AM, 'Nil Geisweiller' via opencog
<opencog@googlegroups.com> wrote:
>
> The spread of the second order distribution shrinks as more evidence
> accumulates, so it depends on the number of observations. There is a
> function to translate the count N (number of observations) into confidence
>
> c = N / (N + K)
>
> so as you may see as the count increases, so does the confidence.

This is a rather weak sigmoid function, located at 'K'. I've often wondered
how well inference chaining would work if one used a sharper formula.
The above *eventually* approaches a confidence of 1.0, but it does
it very slowly.  Pathologically slowly, even.

If I recall correctly, K is hard-coded as 800 in the code.   What if, instead,
one used

c = tanh(N-K/K)

which is a much cleaner, sharper sigmoid centered at K and at least one
web page claims its very very fast, about as fast the simple formula (!!??)
https://txt.arboreus.com/2013/03/29/fast-sigmoid.html

I made a plot, see attached.   The tanh formula in particular looks like it
might give much better results for TV merging in the PLN chainer.

--linas

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Attachment: sigmoid.gplot
Description: Binary data

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