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Network Components FAQ:
Q. What
do Axons do?
A. The Axon family sums all
incoming vectors from multiple connections, and then
applies a transfer function to the sum.
Q. What
does the plain, blank Axon do?
A. This Axon acts the same
as all other Axons, except its transfer function is the
identity function.
Q. What
does a Full Synapse do?
A. A Full Synapse takes its
input and multiplies it by a matrix. If a delay is
specified, the output is delayed by that many time steps.
Q. What
does the straight Synapse do?
A. Using the Straight
synapse to connect two Axons is exactly the same as
making a direct connection between them, except it gives
the additional option of specifying a delay.
Q. What is
that 2nd network that seems to lie on top of the main
network?
A. This is the
backpropagation network. Every Axon and Synapse has a
corresponding BackAxon and BackSynapse which attaches to
the upper right corner of the corresponding forward
component. Data flows forward from the input to the
output through the forward propagation network. The
criterion compares the output with the desired response,
and computes the error. The error is then injected into
the backpropagation network, and the data flows through
this network, back towards the original input.
Q. In the
control palette, what’s the difference between the
clocks with one and two dials?
A. The clocks with one dial
are for use with static networks, where the complete
forward activation and back-propagation cycle can be
completed in the same time step. The clocks with two
dials are dynamic controllers for use with dynamic
networks (see the next question).
Q. When do
I need to use the dynamic controllers?
A. You need to use the
dynamic controllers anytime your network has a feedback
loop with an adaptable weight(s). This includes the Gamma
and Laguarre Axons, which are components that have
internal feedback loops with an adaptable weight. You
also need the dynamic controllers whenever a component
with delays is used at any point in the network other
than the input layer. For example, you can use a static
controller for a network with a TDNN Axon (tapped delay
line) at the input layer, but you must use a dynamic
controller if the TDNN Axon is in the hidden layer.
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