Files
  • main.py
main.py
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import numpy as np

zero = [
  0, 1, 1, 0,
  1, 0, 0, 1,
  1, 0, 0, 1,
  1, 0, 0, 1,
  0, 1, 1, 0
]

one = [
  0, 0, 1, 0,
  0, 0, 1, 0,
  0, 0, 1, 0,
  0, 0, 1, 0,
  0, 0, 1, 0
]

two = [
  0, 1, 1, 0,
  1, 0, 0, 1,
  0, 0, 1, 0,
  0, 1, 0, 0,
  1, 1, 1, 1
]

three = [
  1, 1, 1, 1,
  0, 0, 0, 1,
  0, 1, 1, 1,
  0, 0, 0, 1,
  1, 1, 1, 1
]


predict = [
 0, 1, 1, 0,
 1, 0, 0, 1,
 0, 0, 1, 0,
 0, 1, 0, 0,
 1, 1, 1, 1
]

X = np.array((zero, one, two, three), dtype=float)
y = np.array(([0], [1], [2], [3]), dtype=float)
xPredicted = np.array((predict), dtype=float)

# scale units
y = y/3 # max test score is 100

class Neural_Network(object):
  def __init__(self):
    #parameters
    self.inputSize = 20
    self.outputSize = 1
    self.hiddenSize = 20

    #weights
    self.W1 = np.random.randn(self.inputSize, self.hiddenSize) # (3x2) weight matrix from input to hidden layer
    self.W2 = np.random.randn(self.hiddenSize, self.outputSize) # (3x1) weight matrix from hidden to output layer

  def forward(self, X):
    #forward propagation through our network
    self.z = np.dot(X, self.W1) # dot product of X (input) and first set of 3x2 weights
    self.z2 = self.sigmoid(self.z) # activation function
    self.z3 = np.dot(self.z2, self.W2) # dot product of hidden layer (z2) and second set of 3x1 weights
    o = self.sigmoid(self.z3) # final activation function
    return o

  def sigmoid(self, s):
    # activation function
    return 1/(1+np.exp(-s))

  def sigmoidPrime(self, s):
    #derivative of sigmoid
    return s * (1 - s)

  def backward(self, X, y, o):
    # backward propgate through the network
    self.o_error = y - o # error in output
    self.o_delta = self.o_error*self.sigmoidPrime(o) # applying derivative of sigmoid to error

    self.z2_error = self.o_delta.dot(self.W2.T) # z2 error: how much our hidden layer weights contributed to output error
    self.z2_delta = self.z2_error*self.sigmoidPrime(self.z2) # applying derivative of sigmoid to z2 error

    self.W1 += X.T.dot(self.z2_delta) # adjusting first set (input --> hidden) weights
    self.W2 += self.z2.T.dot(self.o_delta) # adjusting second set (hidden --> output) weights

  def train(self, X, y):
    o = self.forward(X)
    self.backward(X, y, o)

  def predict(self):
    print "Predicted data based on trained weights: ";
    print "Input (scaled): \n" + str(xPredicted);
    print "Actual Output: \n" + str((self.forward(xPredicted))*3);
    print "Rounded Output: \n" + str(round((self.forward(xPredicted))*3));

NN = Neural_Network()
for i in xrange(10000): # trains the NN 100,000 times
  print "#" + str(i) + "\n"
  print "Input: \n" + str(X)
  print "Actual Output: \n" + str(y*3)
  print "Predicted Output: \n" + str(NN.forward(X)*3)
  print "Loss: \n" + str(np.mean(np.square(y - NN.forward(X)))) # mean sum squared loss
  print "\n"
  NN.train(X, y)

NN.predict()
Python 2.7.10 (default, Jul 14 2015, 19:46:27) [GCC 4.8.2] on linux