Machine Learning Fundamentals · free preview

Parameter Initialization

Parameters start at random rather than zero, because zero-initialized weights in a layer make every unit identical and the layer learns one feature, and the distribution's scale controls whether activations and gradients grow or vanish.

1. The failure of zero initialization

The failure of zero initialization

2. The default scaling

The default scaling

3. What goes wrong without the balance

What goes wrong without the balance

4. Why zero initialization fails

A hidden layer of 256 units has every weight initialized to zero and every bias to zero. Training begins with minibatch gradient descent. Which statement describes what happens?

5. The default scale

A weight tensor has fanin=64\text{fan}_{\text{in}} = 64 input units. The common initialization draws weights from a normal distribution with standard deviation 1/fanin\sqrt{1/\text{fan}_{\text{in}}}, which equals ____.

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