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# Recurrent neural network with bias node?

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3 replies to this topic

### #1domokato  Members

Posted 20 April 2012 - 01:17 AM

Hi guys,

I'm trying to use a genetic algorithm to train a recurrent neural network. I kind of understand what bias nodes are for in feed forward networks. Do I need one for a recurrent neural network?

Thanks

### #2Tournicoti  Prime Members

Posted 20 April 2012 - 05:05 AM

Hello domokato

Hi guys,

I'm trying to use a genetic algorithm to train a recurrent neural network. I kind of understand what bias nodes are for in feed forward networks. Do I need one for a recurrent neural network?

Thanks

Yes, for the same reason as for feedforward networks. (it permits to shift the activation function along x axis) .

For example, if I have a 2-inputs unit with 1 recurrent loop (on its output), the input vector is for time n : [ input1n , input2n , outputn-1 , 1 ]. So 4 weights too.
The output is then computed like in a feedfordward network.

Nico

EDIT :

I take this activation function
bool f(float v)
{
return v>0.0f;
}
and I take a unit with 2 boolean inputs with weights equal to 1.

With a bias of 0, the unit performs a OR (input1+input2>0.0)
With a bias of -1, the unit performs a AND (input1+input2-1>0.0)

My point is that a bias must (should) be added to any unit that performs a linear combination of its inputs.

### #3domokato  Members

Posted 22 April 2012 - 02:40 AM

Oh, I get it. Thanks for the explanation

### #4jefferytitan  Members

Posted 23 April 2012 - 12:58 AM

I'm curious, I haven't encountered using a GA to train a neural net before. I guess it's one way to get a large amount of classified training data. How's it working out for you?

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