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simplernn.py
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simplernn.py
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# -*- coding: utf-8 -*-
"""
_____
/ _ \ ** paithon: machine learning framework **
/ / \ \
/ ,,\ \ \
\___/ / / @author: alle.veenstra@gmail.com
s \/
Simple recurrent neural network
"""
import numpy
import math
import matplotlib.pyplot as plt
class RecurrentBackpropagationTrainer:
def __init__(self, network, eta = 0.08, eta_bias = 0.04, eta_L1 = 0, eta_L2 = 0, eta_momentum = 0, eta_decay = 0):
self.network = network
self.eta = eta
self.eta_bias = eta_bias
self.eta_L1 = eta_L1
self.eta_L2 = eta_L2
self.eta_momentum = eta_momentum
self.eta_decay = eta_decay
self.activation = numpy.vectorize(self.activationFunction)
self.derivative = numpy.vectorize(self.derivedActivationFunction)
self.noiser = False
def activationFunction(self, value):
return math.tanh(value)
def derivedActivationFunction(self, value):
# The derived activation function is actually 1 - tanh^2(x)
return 1.0 - value ** 2
def evaluateSerie(self, serie):
out = []
for item in range(len(serie)):
input = numpy.matrix(serie[item]).astype(numpy.float32)
out.append(self.evaluate(input)[0, 0])
return out
def evaluate(self, inputs):
network = self.network
if len(inputs) != network.inputSize - network.hiddenShape[0]:
raise ValueError('Input vector of incorrect size')
# copy the input into the input network activation
input_length = len(inputs)
for k in range(input_length):
network.activations[0][0, k] = inputs[k]
# copy the first hidden layer's activation into the input network activation
for l in range(network.hiddenShape[0]):
network.activations[0][0, input_length + l] = network.activations[1][0, l]
self.feedForward(network)
return network.activations[network.nLayers - 1]
def feedForward(self, network):
for layer in range(1, network.nLayers):
network.activations[layer] = self.activation(network.activations[layer - 1] *
network.weights[layer] +
network.biases[layer])
def train(self, example, classes, epochs):
errors = numpy.zeros(epochs) - 1.0
for epoch in range(epochs):
error = 0
for item in range(len(classes)):
input = numpy.matrix(example[item]).astype(numpy.float32)
target = numpy.matrix(classes[item]).astype(numpy.float32)
# iterate over the sequence
for seq in range(input.shape[1]):
error += self.feedBackward(input[:, seq], target[:, seq])
self.network.reset()
errors[epoch] = math.sqrt(error / len(classes))
return errors[errors > 0]
def feedBackward(self, inputs, target):
network = self.network
if len(target) != network.outputSize:
raise ValueError('Target vector of incorrect size')
self.evaluate(inputs)
self.calculateDeltas(network, target)
self.updateWeights(network)
return numpy.sum(0.5 * numpy.power(network.activations[network.nLayers - 1] - target, 2))
def calculateDeltas(self, network, target):
for layer in reversed(range(1, network.nLayers)):
if layer == network.nLayers - 1:
network.deltas[layer] = numpy.multiply(self.derivative(network.activations[layer]),
(target - network.activations[layer]))
else:
network.deltas[layer] = numpy.multiply(self.derivative(network.activations[layer]),
(network.deltas[layer + 1] * network.weights[layer + 1].T))
network.biases[layer] += network.deltas[layer] * self.eta_bias
def updateWeights(self, network):
for layer in range(1, network.nLayers):
L1 = numpy.sign(network.activations[layer]) * -self.eta_L1
L2 = network.activations[layer] * -self.eta_L2
update = (network.activations[layer - 1].T * (network.deltas[layer] + L1 + L2))
update += network.previousUpdate[layer] * self.eta_momentum
update -= network.weights[layer] * self.eta_decay
network.weights[layer] += update
network.previousUpdate[layer] = update
def verifyGradient(self, input, target):
network = self.network
epsilon = 0.0001
differences = []
self.feedBackward(input, target)
for layer in range(1, network.nLayers):
savedWeight = numpy.copy(network.weights[layer])
for i in range(network.size[layer - 1]):
for j in range(network.size[layer]):
positive = numpy.copy(savedWeight)
positive[i, j] += epsilon
network.weights[layer] = positive
output = self.evaluate(input)
errorP1 = 0.5 * (numpy.sum((output - target) ** 2))
negative = numpy.copy(savedWeight)
negative[i, j] -= epsilon
network.weights[layer] = negative
output = self.evaluate(input)
errorP2 = 0.5 * (numpy.sum((output - target) ** 2))
approx = (errorP1 - errorP2) / (epsilon * 2)
gradient = -(network.activations[layer - 1][0, i] * network.deltas[layer][0, j])
differences.append(numpy.abs(gradient - approx))
network.weights[layer] = savedWeight
return numpy.mean(differences)
class SimpleRecurrentNetwork:
def __init__(self, inputSize, hiddenShape = [], outputSize = 1):
self.inputSize = inputSize + hiddenShape[0]
self.outputSize = outputSize
hiddenShape.append(outputSize)
self.hiddenSize = len(hiddenShape)
self.hiddenShape = hiddenShape
self.nLayers = 1 + self.hiddenSize
self.size = {}
self.activations = {}
self.biases = {}
self.previousUpdate = {}
self.weights = {}
self.deltas = {}
self.size[0] = inputSize
self.activations[0] = (numpy.matrix(0 - numpy.ones(self.inputSize)).astype(numpy.float32))
for i in range(self.hiddenSize):
if i == 0:
prevLayerSize = self.inputSize
else:
prevLayerSize = self.hiddenShape[i - 1]
layerSize = self.hiddenShape[i]
self.size[i + 1] = layerSize
self.previousUpdate[i + 1] = (numpy.matrix(numpy.zeros((prevLayerSize, layerSize))).astype(numpy.float32))
self.weights[i + 1] = (numpy.matrix(numpy.random.normal(0, 0.5, (prevLayerSize, layerSize))).astype(numpy.float32))
self.activations[i + 1] = (numpy.matrix(numpy.ones(layerSize)).astype(numpy.float32))
self.biases[i + 1] = (numpy.matrix(numpy.random.normal(0, 0.5, layerSize)).astype(numpy.float32))
def reset(self):
self.activations[1] = (numpy.matrix(numpy.ones(self.hiddenShape[0])).astype(numpy.float32))
def plot_vector(errors, n):
plt.subplot(2, 2, n)
plt.plot(range(len(errors)), errors)
if n == 4:
plt.show()
factor = 8.0
input = numpy.matrix(range(200)).astype(numpy.float32) / factor
input_sin = ((numpy.sin(input)) * 0.5).tolist()
output_sin = ((numpy.sin(input * 2)) * 0.5).tolist()
network = SimpleRecurrentNetwork(1, [8], 1)
trainer = RecurrentBackpropagationTrainer(network)
trainer.eta = 0.08
trainer.eta_bias = 0
trainer.eta_decay = 0
examples = input_sin
classes = output_sin
errors = trainer.train(examples, classes, 100)
x = trainer.evaluateSerie(input_sin[0])
plot_vector(errors, 1)
plot_vector(input_sin[0], 2)
plot_vector(output_sin[0], 3)
plot_vector(x, 4)