Number of neurons in multiplication example


#1

I’m looking at the nengo multiplication.ipynb example (also here). Why does the combined ensemble have 220 neurons?

The incoming ensembles each have 100 neurons, so I would expect the combined to have 200 neurons instead.


#2

The number of neurons in the combined ensemble is independent of the number of neurons in the input ensembles. Rather, the number of neurons in the combined ensemble determines how well it is able to represent the 2-dimensional value required to perform the multiplication. Increasing the number of neurons in the combined ensemble will increase the accuracy of the multiplication, and decreasing the number of neurons will decrease the accuracy of the multiplication.

As a side note, the multiplicative ensembles in Spaun use 150 neurons (with 50 neurons for the input ensembles).