class NeuralNetwork:
# publicly accessed and altered later so starting learning rate doesn't really matter
LEARNING_RATE = 0.05
def __init__(self, num_inputs, num_hidden, num_outputs, multiply = None, hidden_layer_weights = None, hidden_layer_bias = None, output_layer_weights = None, output_layer_bias = None):
self.num_inputs = num_inputs
# create neuron layer from the neuronLayer class
self.hidden_layer = NeuronLayer(num_hidden, hidden_layer_bias)
# add multiply parameter here to signify that multiplcation problem is being addressed
self.output_layer = NeuronLayer(num_outputs, output_layer_bias, multiply)
# two different methods for hidden layer weights and output layer weights
self.init_weights_from_inputs_to_hidden_layer_neurons(hidden_layer_weights)
self.init_weights_from_hidden_layer_neurons_to_output_layer_neurons(output_layer_weights)
def init_weights_from_inputs_to_hidden_layer_neurons(self, hidden_layer_weights):
weight_num = 0
for h in range(len(self.hidden_layer.neurons)):
for i in range(self.num_inputs):
if not hidden_layer_weights:
self.hidden_layer.neurons[h].weights.append(random.random())
else:
self.hidden_layer.neurons[h].weights.append(hidden_layer_weights[weight_num])
weight_num += 1
def init_weights_from_hidden_layer_neurons_to_output_layer_neurons(self, output_layer_weights):
weight_num = 0
for o in range(len(self.output_layer.neurons)):
for h in range(len(self.hidden_layer.neurons)):
if not output_layer_weights:
self.output_layer.neurons[o].weights.append(random.random())
else:
self.output_layer.neurons[o].weights.append(output_layer_weights[weight_num])
weight_num += 1
# print current information in the net
def inspect(self):
print('------')
print('* Inputs: {}'.format(self.num_inputs))
print('------')
print('Hidden Layer')
self.hidden_layer.inspect()
print('------')
print('* Output Layer')
self.output_layer.inspect()
print('------')
def feed_forward(self, inputs):
hidden_layer_outputs = self.hidden_layer.feed_forward(inputs)
return self.output_layer.feed_forward(hidden_layer_outputs)
# use online learning to update the weights after each training case
def train(self, training_inputs, training_outputs):
self.feed_forward(training_inputs)
# output neuron deltas
pd_errors_wrt_output_neuron_total_net_input = [0] * len(self.output_layer.neurons)
for o in range(len(self.output_layer.neurons)):
# ∂E/∂zⱼ
pd_errors_wrt_output_neuron_total_net_input[o] = self.output_layer.neurons[o].calculate_pd_error_wrt_total_net_input(training_outputs[o])
# hidden neuron deltas
pd_errors_wrt_hidden_neuron_total_net_input = [0] * len(self.hidden_layer.neurons)
for h in range(len(self.hidden_layer.neurons)):
# need to calculate the derivative of the error with respect to the output of each hidden layer neuron
# dE/dyⱼ = Σ ∂E/∂zⱼ * ∂z/∂yⱼ = Σ ∂E/∂zⱼ * wᵢⱼ
d_error_wrt_hidden_neuron_output = 0
for o in range(len(self.output_layer.neurons)):
d_error_wrt_hidden_neuron_output += pd_errors_wrt_output_neuron_total_net_input[o] * self.output_layer.neurons[o].weights[h]
# ∂E/∂zⱼ = dE/dyⱼ * ∂zⱼ/∂
pd_errors_wrt_hidden_neuron_total_net_input[h] = d_error_wrt_hidden_neuron_output * self.hidden_layer.neurons[h].calculate_pd_total_net_input_wrt_input()
# update output neuron weights
for o in range(len(self.output_layer.neurons)):
for w_ho in range(len(self.output_layer.neurons[o].weights)):
# ∂Eⱼ/∂wᵢⱼ = ∂E/∂zⱼ * ∂zⱼ/∂wᵢⱼ
pd_error_wrt_weight = pd_errors_wrt_output_neuron_total_net_input[o] * self.output_layer.neurons[o].calculate_pd_total_net_input_wrt_weight(w_ho)
# Δw = α * ∂Eⱼ/∂wᵢ
self.output_layer.neurons[o].weights[w_ho] -= self.LEARNING_RATE * pd_error_wrt_weight
# update hidden neuron weights
for h in range(len(self.hidden_layer.neurons)):
for w_ih in range(len(self.hidden_layer.neurons[h].weights)):
# ∂Eⱼ/∂wᵢ = ∂E/∂zⱼ * ∂zⱼ/∂wᵢ
pd_error_wrt_weight = pd_errors_wrt_hidden_neuron_total_net_input[h] * self.hidden_layer.neurons[h].calculate_pd_total_net_input_wrt_weight(w_ih)
# Δw = α * ∂Eⱼ/∂wᵢ
self.hidden_layer.neurons[h].weights[w_ih] -= self.LEARNING_RATE * pd_error_wrt_weight
# calculate the total error so we can test and try to minimize it
def calculate_total_error(self, training_sets):
total_error = 0
for t in range(len(training_sets)):
training_inputs, training_outputs = training_sets[t]
self.feed_forward(training_inputs)
for o in range(len(training_outputs)):
total_error += self.output_layer.neurons[o].calculate_error(training_outputs[o])
return total_error
class NeuralNetwork:
def __init__(self,
num_hidden_layer,
total_inputs,
total_outputs,
bias_hidden_layer=None,
bias_output_layer=None,
learning_rate=None):
self.total_inputs = total_inputs
self.learning_rate = learning_rate if learning_rate else 0.5
self.hidden_layer = NeuronLayer(num_hidden_layer, bias_hidden_layer)
self.output_layer = NeuronLayer(total_outputs, bias_output_layer)
self.init_weight_hidden_layer()
self.init_output_hidden_layer()
def init_weight_hidden_layer(self):
for index_hidden_layer in range(len(self.hidden_layer.neurons)):
for index_total_inputs in range(self.total_inputs):
self.hidden_layer.neurons[index_hidden_layer].weights.append(
random.random())
def init_output_hidden_layer(self):
for index_output_layer in range(len(self.output_layer.neurons)):
for index_hidden_layer in range(len(self.hidden_layer.neurons)):
self.output_layer.neurons[index_output_layer].weights.append(
random.random())
def feed_forward(self, inputs):
hidden_layer_outputs = self.hidden_layer.feed_forward(inputs)
return self.output_layer.feed_forward(hidden_layer_outputs)
def training(self, training_inputs, training_outputs):
self.feed_forward(training_inputs)
error_output_layer = self.find_error_output_layer(training_outputs)
error_hidden_layer = self.find_error_hidden_layer(error_output_layer)
self.update_output_layer_weights(error_output_layer)
self.update_hidden_layer_weights(error_hidden_layer)
def find_error_output_layer(self, training_outputs):
error_output_layer = [0] * len(self.output_layer.neurons)
for index_output_layer in range(len(self.output_layer.neurons)):
error_output_layer[index_output_layer] = self.output_layer.neurons[
index_output_layer].get_error_from_expected_output(
training_outputs[index_output_layer])
return error_output_layer
def find_error_hidden_layer(self, errors_output_layer):
errors_hidden_layer = [0] * len(self.hidden_layer.neurons)
for index in range(len(self.hidden_layer.neurons)):
sum_expected_weight = 0
for index_output_layer in range(len(self.output_layer.neurons)):
sum_expected_weight += errors_output_layer[
index_output_layer] * self.output_layer.neurons[
index_output_layer].weights[index]
errors_hidden_layer[
index] = sum_expected_weight * self.hidden_layer.neurons[
index].calculate_o()
return errors_hidden_layer
def update_hidden_layer_weights(self, error_output_layer):
for index in range(len(self.hidden_layer.neurons)):
for w_index in range(len(
self.hidden_layer.neurons[index].weights)):
error_weight = error_output_layer[
index] * self.hidden_layer.neurons[
index].get_input_by_index(w_index)
self.hidden_layer.neurons[index].weights[
w_index] -= self.learning_rate * error_weight
def update_output_layer_weights(self, error_hidden_layer):
for index in range(len(self.output_layer.neurons)):
for w_index in range(len(
self.output_layer.neurons[index].weights)):
error_weight = error_hidden_layer[
index] * self.output_layer.neurons[
index].get_input_by_index(w_index)
self.output_layer.neurons[index].weights[
w_index] -= self.learning_rate * error_weight