Week 2 Exercise 3 - initialize_velocity

Course Q&A Deep Learning Specialization Improving Deep Neural Networks: Hyperparameter tun
1

may i ask why i use this to set to 0 is not correct?
v[“dW” + str(l)] = np.zeros(np.shape(parameters[“W” + str(L)]))

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2

Assuming that you use right quotations, there is a capital “L” instead of “l”.

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3

Why do you do that? The for loop runs to the correct range.

Here’s the assignment code as in the notebook:

# GRADED FUNCTION: initialize_velocity

def initialize_velocity(parameters):
    """
    Initializes the velocity as a python dictionary with:
                - keys: "dW1", "db1", ..., "dWL", "dbL" 
                - values: numpy arrays of zeros of the same shape as the corresponding gradients/parameters.
    Arguments:
    parameters -- python dictionary containing your parameters.
                    parameters['W' + str(l)] = Wl
                    parameters['b' + str(l)] = bl
    
    Returns:
    v -- python dictionary containing the current velocity.
                    v['dW' + str(l)] = velocity of dWl
                    v['db' + str(l)] = velocity of dbl
    """
    
    L = len(parameters) // 2 # number of layers in the neural networks
    v = {}
    
    # Initialize velocity
    for l in range(1, L + 1):
        # (approx. 2 lines)
        # v["dW" + str(l)] =
        # v["db" + str(l)] =
        # YOUR CODE STARTS HERE
        
        
        # YOUR CODE ENDS HERE
        
    return v