diff --git a/neural-networks/seminarpaper.tex b/neural-networks/seminarpaper.tex index 40755dc..f07706c 100644 --- a/neural-networks/seminarpaper.tex +++ b/neural-networks/seminarpaper.tex @@ -370,23 +370,34 @@ the respective synapse. \label{tab:mrs-synapse} \end{table} -Modulated random search means essentially random weight changes. Each synapse +Modulated random search means essentially random weight changes. Each synapse \(i\) has some parameters that are used (see table \ref{tab:mrs-synapse}). The weight -change probability is the product of the intrinsic weight change probability -and the concentration of the neuromodulator the synapse is sensitive to -at its location. Additionally the maximum neuromodulator sensitivity is -the ceiling for the second part of that product. This means there is a maximum -weight change probability for each synapse. Should a weight change occur a new -weight is chosen randomly from the range of values described by the minimum and -maximum weight of the synapse. +change probability \(p_i^w\) at time \(t\) is the product of the intrinsic weight +change probability \(W_i\) and the concentration of the neuromodulator the synapse +is sensitive to \(c(t, x_i, y_i)\) at its location \((x_i, y_i)\). Additionally +the maximum neuromodulator sensitivity \(M_i\) is the ceiling for the second part +of that product. This means there is a maximum weight change probability for each +synapse. Weight changes can happen at any time step. Therefore the intrinsic weight +change probability has to be very small. Should a weight change occur a new weight +\(w_i\) is chosen randomly from the interval \([W_i^{min}, W_i^{max}]\). + + +\[ + p_i^w = min(M_i, c(t, x_i, y_i)) \cdot W_i,\; 0 < W_i \lll 1 +\] Moreover a synapse can disable or enable itself. The actual disable/enable -probability is the product of the intrinsic value saved as parameter and -the neuromodulator concentration. The concentration is again ceiled by the -maximum sensitivity limit given as parameter. This means there is a maximum -disable/enable probability as well. A disabled synapse is treated as having -weight 0 but the actual value is stored so that it can be restored when the -synapse is enabled again. +probability \(p_i^d\) is the product of the intrinsic value \(D_i\) saved as +parameter and the neuromodulator concentration \(c(t, x_i, y_i)\). The concentration +is again ceiled by the maximum sensitivity limit \(M_i\) given as parameter. +This means there is a maximum disable/enable probability as well. The intrinsic +enable/disable probability must be smaller than the intrinsic weight change probability. +A disabled synapse is treated as having weight 0 but the actual value is stored +so that it can be restored when the synapse is enabled again. + +\[ + p_i^d = min(M_i, c(t, x_i, y_i) \cdot D_i,\; 0 \leq D_i < W_i +\] Given a so called neural network structure or substrate this makes it easier to find different network topologies (structure and weights combined). @@ -401,7 +412,11 @@ but rather the difference to be added to the current weight is sampled from a normal distribution with a mean of zero and \(\sigma^2\)-variance. The sampled value could be infinitely large and hence the new weight outside of the given bounds for it. Therefore the value is sampled until the sum of the -current weight and the sampled value are within the range. +current weight and the sampled value are within the interval \([W_i^{min}, W_i^{max}]\). + +\[ + w_i (t + 1) = w_i (t) + \Delta w_i \;\text{where}\; \Delta w_i \sim \mathcal{N}(0, \sigma^2) +\] Toutunji and Pasemann implemented a mechanism for disabling synapses in the modulated gaussian walk as well but did not make use of it later and