setTransferFunction in scripting causes nerd to freeze

[htoutounji]

I am writing a script for a transfer function on nerd where I change the bias term according to some learning rule. I still want to use the hyperbolic tangent transfer function. Loading the following script is causing nerd to freeze:

var inSynapses;

function reset() {
net.setTransferFunction(neuron, "tanh");
inSynapses = net.getInSynapses(neuron);
}

function calc(activation) {
activation =
theta = net.getBias(neuron);

sumW = 0.0;
for (var i=0; i < inSynapses.length; ++i) {
sumW += net.getWeight(inSynapses[i]);
}

theta -= eta*(theta + sumW);
net.setBias(neuron,theta);

//nerd.error(getTransferFunctionName(206));

return activation;

}

loading the same script but with the statement "net.setTransferFunction(neuron, "tanh");" commented works. Uncommenting it after loading also causes freeze. Is it a bug or am I using the statement wrongly?

[cybott]

You cannot replace the scripted transfer function during its own reset()
call by another transfer function. This will lead to undefined behavior
(actually, it should generate a warning instead of a freeze :) ).

Instead, do not use an external transfer function to calculate the
tanh(). Just call a custom local function myTanh() in which you
implement the tanh equation, and return its result, e.g.

return myTanh(activation);

However, it seems not necessary to use a ScriptedTranserFunction for
this job. You could also use a ScriptedActivationFunction. In that case,
you can use the setDefaultActiationFunction() method (see documentation
http://www.ultopia.de/drupal/nerddoc/node/78#setDefaultActivationFunction).

On 10/08/2013 05:07 PM, htoutounji wrote:

I am writing a script for a transfer function on nerd where I change
the bias term according to some learning rule. I still want to use the
hyperbolic tangent transfer function. Loading the following script is
causing nerd to freeze:

var inSynapses;

function reset() {
net.setTransferFunction(neuron, "tanh");
inSynapses = net.getInSynapses(neuron);
}

function calc(activation) {
activation =
theta = net.getBias(neuron);

sumW = 0.0;
for (var i=0; i < inSynapses.length; ++i) {
sumW += net.getWeight(inSynapses[i]);
}

|theta -= eta*(theta + sumW);
net.setBias(neuron,theta);

//nerd.error(getTransferFunctionName(206));

return activation;
|

}

loading the same script but with the statement
"net.setTransferFunction(neuron, "tanh");" commented works.
Uncommenting it after loading also causes freeze. Is it a bug or am I
using the statement wrongly?

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[htoutounji]

Thanks! I'll write a local function then.

The reason why I am not using ScriptedActivationFunction is that the theta dynamics I am trying to implement are on top of SRN and I didn't want to rewrite the SRN activation dynamics. I could set it as default but then I will lose the interface to observe variables and change equations and parameters. Also, these theta dynamics cannot be implemented with a single formula in the scripted SRN version because it needs to sum up incoming weights to the neuron which requires a for-loop.