refactor(network.py): annotate Neuron constructor (comments other functions)

network.py

@@ -1,6 +1,7 @@
 import math
 import random
 
+
 def sigmoid(x: float) -> float:
     return 1 / (1 + math.exp(-x))
 
@@ -9,123 +10,154 @@ def sigmoid_deriv(x: float) -> float:
     y: float = sigmoid(x)
     return y * (1 - y)
 
-# neuron class
+
 class Neuron:
-    """
+    def __init__(self, input_size: int) -> None:
-    z                   : linear combination of inputs and weights plus bias (pre-activation)
-    y                   : output of the activation function (sigmoid(z))
-    w                   : list of weights, one for each input
-    """
-    def __init__(self, isize):
-        # number of inputs to this neuron
-        self.isize = isize
-        # importance to each input
-        self.weight = [random.uniform(-1, 1) for _ in range(self.isize)]
-        # importance of the neuron
-        self.bias = random.uniform(-1, 1)
-
-    def forward(self, x, activate=True):
         """
-        x               : list of input values to the neuron
+        Set up the neuron's parameters (weights, and bias)
+
+        :param input_size: Number of incomming inputs (must be > 0)
         """
-        # computes the weighted sum of inputs and add the bias
+        # Store input dimensions for structural consistency
-        self.z = sum(w * xi for w, xi in zip(self.weight, x)) + self.bias
+        self._input_size: int = input_size
-        # normalize the output between 0 and 1 if activate
-        last_output = sigmoid(self.z) if activate else self.z
 
-        return last_output
+        # Scale each input influence using random weights.
+        self._weight: list[float] = [
+            random.uniform(-1., 1.) for _ in range(input_size)
+        ]
 
-    # adjust weight and bias of neuron
+        # Initialize a shift to the activation threshold with a random bias
-    def backward(self, x, dcost_dy, learning_rate):
+        self._bias: float = random.uniform(-1., 1.)
-        """
-        x               : list of input values to the neuron  
-        dcost_dy        : derivate of the cost function `(2 * (output - target))`
-        learning_rate   : learning factor (adjust the speed of weight/bias change during training)
 
-        weight -= learning_rate * dC/dy * dy/dz * dz/dw
+    def __repr__(self) -> str:
-        bias   -= learning_rate * dC/dy * dy/dz * dz/db
+        jmp: int = int(math.sqrt(self._input_size))
-        """
+        text: list[str] = []
-        # dy/dz: derivate of the sigmoid activation
-        dy_dz = sigmoid_deriv(self.z)
-        # dz/dw = x
-        dz_dw = x
 
-        assert len(dz_dw) >= self.isize, "too many value for input size"
+        for i in range(0, self._input_size, jmp):
+            line: str = str.join("", str(self._weight[i: (i + jmp)]))
+            text.append(line)
 
-        # dz/db = 1
+        return f"weight:\n{str.join("\n", text)}\nbias: {self._bias}"
-        dz_db = 1
 
-        for i in range(self.isize):
+# # neuron class
-            # update each weight `weight -= learning_rate * dC/dy * dy/dz * x_i`
+# class Neuron:
-            self.weight[i] -= learning_rate * dcost_dy * dy_dz * dz_dw[i]
+#     """
+#     z                   : linear combination of inputs and weights plus bias (pre-activation)
+#     y                   : output of the activation function (sigmoid(z))
+#     w                   : list of weights, one for each input
+#     """
+#     def __init__(self, input_size):
+#         # number of inputs to this neuron
+#         self._input_size = input_size
+#         # importance to each input
+#         self._weight = [random.uniform(-1, 1) for _ in range(self._input_size)]
+#         # importance of the neuron
+#         self._bias = random.uniform(-1, 1)
 
-        # update bias: bias -= learning_rate * dC/dy * dy/dz * dz/db
+#     def forward(self, x, activate=True):
-        self.bias -= learning_rate * dcost_dy * dy_dz * dz_db
+#         """
+#         x               : list of input values to the neuron
+#         """
+#         # computes the weighted sum of inputs and add the bias
+#         self._z = sum(w * xi for w, xi in zip(self.weight, x)) + self.bias
+#         # normalize the output between 0 and 1 if activate
+#         last_output = sigmoid(self.z) if activate else self.z
 
-        # return gradient vector len(input) dimension
+#         return last_output
-        return [dcost_dy * dy_dz * w for w in self.weight]
 
+#     # adjust weight and bias of neuron
+#     def backward(self, x, dcost_dy, learning_rate):
+#         """
+#         x               : list of input values to the neuron
+#         dcost_dy        : derivate of the cost function `(2 * (output - target))`
+#         learning_rate   : learning factor (adjust the speed of weight/bias change during training)
 
-class Layer:
+#         weight -= learning_rate * dC/dy * dy/dz * dz/dw
-    def __init__(self, input_size, output_size):
+#         bias   -= learning_rate * dC/dy * dy/dz * dz/db
-        """
+#         """
-        input_size      : size of each neuron input
+#         # dy/dz: derivate of the sigmoid activation
-        output_size     : size of neurons
+#         dy_dz = sigmoid_deriv(self.z)
-        """
+#         # dz/dw = x
-        self.size = output_size
+#         dz_dw = x
-        # list of neurons
-        self.neurons = [Neuron(input_size) for _ in range(output_size)]
 
-    def forward(self, inputs, activate=True):
+#         assert len(dz_dw) >= self.isize, "too many value for input size"
-        self.inputs = inputs
-        #  give the same inputs to each neuron in the layer
-        return [neuron.forward(inputs, activate) for neuron in self.neurons]
 
-    # adjust weight and bias of the layer (all neurons)
+#         # dz/db = 1
-    def backward(self, dcost_dy_list, learning_rate=0.1):
+#         dz_db = 1
-        # init layer gradient vector len(input) dimention
-        input_gradients = [0.0] * len(self.inputs)
 
-        for i, neuron in enumerate(self.neurons):
+#         for i in range(self.isize):
-            dcost_dy = dcost_dy_list[i]
+#             # update each weight `weight -= learning_rate * dC/dy * dy/dz * x_i`
-            grad_to_input = neuron.backward(self.inputs, dcost_dy, learning_rate)
+#             self.weight[i] -= learning_rate * dcost_dy * dy_dz * dz_dw[i]
 
-            # accumulate the input gradients from all neurons
+#         # update bias: bias -= learning_rate * dC/dy * dy/dz * dz/db
-            for j in range(len(grad_to_input)):
+#         self.bias -= learning_rate * dcost_dy * dy_dz * dz_db
-                input_gradients[j] += grad_to_input[j]
 
-        # return layer gradient
+#         # return gradient vector len(weight) dimension
-        return input_gradients
+#         return [dcost_dy * dy_dz * w for w in self.weight]
 
-class NeuralNetwork:
+#     def __repr__(self):
-    def __init__(self, layer_size):
+#         pass
-        self.layers = [Layer(layer_size[i], layer_size[i+1]) for i in range(len(layer_size) - 1)]
 
-    def forward(self, inputs):
+# class Layer:
-        output = inputs
+#     def __init__(self, input_size, output_size):
-        for i, layer in enumerate(self.layers):
+#         """
-            activate = (i != len(self.layers) - 1)  # deactivate sigmoid latest neuron
+#         input_size      : size of each neuron input
-            output = layer.forward(output, activate=activate)
+#         output_size     : size of neurons
-        return output
+#         """
+#         self.size = output_size
+#         # list of neurons
+#         self.neurons = [Neuron(input_size) for _ in range(output_size)]
 
-    def backward(self, inputs, targets, learning_rate=0.1):
+#     def forward(self, inputs, activate=True):
-        """
+#         self.inputs = inputs
-        target must be a list with the same length that the final layer
+#         #  give the same inputs to each neuron in the layer
-        input
+#         return [neuron.forward(inputs, activate) for neuron in self.neurons]
-        """
-        output = self.forward(inputs)
 
-        # computes the initial gradient of the cost function for each neuron
+#     # adjust weight and bias of the layer (all neurons)
-        # by using Mean Squared Error's derivate: dC/dy = 2 * (output - target)
+#     def backward(self, dcost_dy_list, learning_rate=0.1):
-        dcost_dy_list = [2 * (o - t) for o, t in zip(output, targets)]
+#         # init layer gradient vector len(input) dimention
+#         input_gradients = [0.0] * len(self.inputs)
 
-        grad = dcost_dy_list
+#         for i, neuron in enumerate(self.neurons):
-        for layer in reversed(self.layers):
+#             dcost_dy = dcost_dy_list[i]
-            # backpropagate the gradient of the layer to update weights and biases
+#             grad_to_input = neuron.backward(self.inputs, dcost_dy, learning_rate)
-            grad = layer.backward(grad, learning_rate)
 
-        # return final gradient 
+#             # accumulate the input gradients from all neurons
-        return grad
+#             for j in range(len(grad_to_input)):
+#                 input_gradients[j] += grad_to_input[j]
 
-if __name__ == "__main__":
+#         # return layer gradient
-    print("you might want to run main.py instead of network.py")
+#         return input_gradients
+
+# class NeuralNetwork:
+#     def __init__(self, layer_size):
+#         self.layers = [Layer(layer_size[i], layer_size[i+1]) for i in range(len(layer_size) - 1)]
+
+#     def forward(self, inputs):
+#         output = inputs
+#         for i, layer in enumerate(self.layers):
+#             activate = (i != len(self.layers) - 1)  # deactivate sigmoid latest neuron
+#             output = layer.forward(output, activate=activate)
+#         return output
+
+#     def backward(self, inputs, targets, learning_rate=0.1):
+#         """
+#         target must be a list with the same length that the final layer
+#         input
+#         """
+#         output = self.forward(inputs)
+
+#         # computes the initial gradient of the cost function for each neuron
+#         # by using Mean Squared Error's derivate: dC/dy = 2 * (output - target)
+#         dcost_dy_list = [2 * (o - t) for o, t in zip(output, targets)]
+
+#         grad = dcost_dy_list
+#         for layer in reversed(self.layers):
+#             # backpropagate the gradient of the layer to update weights and biases
+#             grad = layer.backward(grad, learning_rate)
+
+#         # return final gradient
+#         return grad
+
+# if __name__ == "__main__":
+#     print("you might want to run main.py instead of network.py")