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431

answers:

3

Is a Neural network with 2 input nodes, 2 hidden nodes and an output supposed to be able to solve the XOR problem provided there is no bias? Or can it get stuck?

+1  A: 

If I remember correctly it's not possible to have XOR without a bias.

Georg
I have a (I hope working) neural network class that seems to be able to solve it with 2 inputs 3 hidden neurons and 1 output, but can't with 2 hidden neurons. Is it enough when calculating net = w1x1 + w2x2 to just add 1 to the equation, net = w1x1 + w2x2 + 1, or that is still not enough? do i have to have the 3rd weight? Thanks
devoured elysium
I think that in your example with 3 hidden neurons one of the neurons acts like a bias, that's why it works. I can't think of an example that would work with 2 hidden nodes. What's the reason not to use a bias?
Georg
+1  A: 

Leave the bias in. It doesn't see the values of your inputs.

In terms of a one-to-one analogy, I like to think of the bias as the offsetting c-value in the straight line equation: y = mx + c; it adds an independent degree of freedom to your system that is not influenced by the inputs to your network.

Zaid
A: 

Hello,

I have built a neural network without bias and a 2x2x1 architecture solves XOR in 280 epochs. Am new to this, so didn't know either way, but it works, so it is possible.

Regards,

Katya