Mercurial > ift6266
annotate baseline/mlp/mlp_nist.py @ 368:d391ad815d89
Correction d'un bug avec la fonction de log-likelihood pour utilisation de non-linearite de sortie sigmoides
author | SylvainPL <sylvain.pannetier.lebeuf@umontreal.ca> |
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date | Fri, 23 Apr 2010 12:12:03 -0400 |
parents | 76b7182dd32e |
children | 60a4432b8071 |
rev | line source |
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110 | 1 """ |
2 This tutorial introduces the multilayer perceptron using Theano. | |
3 | |
4 A multilayer perceptron is a logistic regressor where | |
5 instead of feeding the input to the logistic regression you insert a | |
6 intermidiate layer, called the hidden layer, that has a nonlinear | |
7 activation function (usually tanh or sigmoid) . One can use many such | |
8 hidden layers making the architecture deep. The tutorial will also tackle | |
9 the problem of MNIST digit classification. | |
10 | |
11 .. math:: | |
12 | |
13 f(x) = G( b^{(2)} + W^{(2)}( s( b^{(1)} + W^{(1)} x))), | |
14 | |
15 References: | |
16 | |
17 - textbooks: "Pattern Recognition and Machine Learning" - | |
18 Christopher M. Bishop, section 5 | |
19 | |
20 TODO: recommended preprocessing, lr ranges, regularization ranges (explain | |
21 to do lr first, then add regularization) | |
22 | |
23 """ | |
24 __docformat__ = 'restructedtext en' | |
25 | |
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26 import sys |
110 | 27 import pdb |
28 import numpy | |
29 import pylab | |
30 import theano | |
31 import theano.tensor as T | |
32 import time | |
33 import theano.tensor.nnet | |
143
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34 import pylearn |
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35 import theano,pylearn.version,ift6266 |
110 | 36 from pylearn.io import filetensor as ft |
322 | 37 from ift6266 import datasets |
110 | 38 |
39 data_path = '/data/lisa/data/nist/by_class/' | |
40 | |
41 class MLP(object): | |
42 """Multi-Layer Perceptron Class | |
43 | |
44 A multilayer perceptron is a feedforward artificial neural network model | |
45 that has one layer or more of hidden units and nonlinear activations. | |
46 Intermidiate layers usually have as activation function thanh or the | |
47 sigmoid function while the top layer is a softamx layer. | |
48 """ | |
49 | |
50 | |
51 | |
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52 def __init__(self, input, n_in, n_hidden, n_out,learning_rate): |
110 | 53 """Initialize the parameters for the multilayer perceptron |
54 | |
55 :param input: symbolic variable that describes the input of the | |
56 architecture (one minibatch) | |
57 | |
58 :param n_in: number of input units, the dimension of the space in | |
59 which the datapoints lie | |
60 | |
61 :param n_hidden: number of hidden units | |
62 | |
63 :param n_out: number of output units, the dimension of the space in | |
64 which the labels lie | |
65 | |
66 """ | |
67 | |
68 # initialize the parameters theta = (W1,b1,W2,b2) ; note that this | |
69 # example contains only one hidden layer, but one can have as many | |
70 # layers as he/she wishes, making the network deeper. The only | |
71 # problem making the network deep this way is during learning, | |
72 # backpropagation being unable to move the network from the starting | |
73 # point towards; this is where pre-training helps, giving a good | |
74 # starting point for backpropagation, but more about this in the | |
75 # other tutorials | |
76 | |
77 # `W1` is initialized with `W1_values` which is uniformely sampled | |
78 # from -6./sqrt(n_in+n_hidden) and 6./sqrt(n_in+n_hidden) | |
79 # the output of uniform if converted using asarray to dtype | |
80 # theano.config.floatX so that the code is runable on GPU | |
81 W1_values = numpy.asarray( numpy.random.uniform( \ | |
82 low = -numpy.sqrt(6./(n_in+n_hidden)), \ | |
83 high = numpy.sqrt(6./(n_in+n_hidden)), \ | |
84 size = (n_in, n_hidden)), dtype = theano.config.floatX) | |
85 # `W2` is initialized with `W2_values` which is uniformely sampled | |
86 # from -6./sqrt(n_hidden+n_out) and 6./sqrt(n_hidden+n_out) | |
87 # the output of uniform if converted using asarray to dtype | |
88 # theano.config.floatX so that the code is runable on GPU | |
89 W2_values = numpy.asarray( numpy.random.uniform( | |
90 low = -numpy.sqrt(6./(n_hidden+n_out)), \ | |
91 high= numpy.sqrt(6./(n_hidden+n_out)),\ | |
92 size= (n_hidden, n_out)), dtype = theano.config.floatX) | |
93 | |
94 self.W1 = theano.shared( value = W1_values ) | |
95 self.b1 = theano.shared( value = numpy.zeros((n_hidden,), | |
96 dtype= theano.config.floatX)) | |
97 self.W2 = theano.shared( value = W2_values ) | |
98 self.b2 = theano.shared( value = numpy.zeros((n_out,), | |
99 dtype= theano.config.floatX)) | |
100 | |
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101 #include the learning rate in the classifer so |
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102 #we can modify it on the fly when we want |
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103 lr_value=learning_rate |
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104 self.lr=theano.shared(value=lr_value) |
110 | 105 # symbolic expression computing the values of the hidden layer |
106 self.hidden = T.tanh(T.dot(input, self.W1)+ self.b1) | |
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107 |
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108 |
110 | 109 |
110 # symbolic expression computing the values of the top layer | |
111 self.p_y_given_x= T.nnet.softmax(T.dot(self.hidden, self.W2)+self.b2) | |
112 | |
113 # compute prediction as class whose probability is maximal in | |
114 # symbolic form | |
115 self.y_pred = T.argmax( self.p_y_given_x, axis =1) | |
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116 self.y_pred_num = T.argmax( self.p_y_given_x[0:9], axis =1) |
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117 |
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118 |
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119 |
110 | 120 |
121 # L1 norm ; one regularization option is to enforce L1 norm to | |
122 # be small | |
123 self.L1 = abs(self.W1).sum() + abs(self.W2).sum() | |
124 | |
125 # square of L2 norm ; one regularization option is to enforce | |
126 # square of L2 norm to be small | |
127 self.L2_sqr = (self.W1**2).sum() + (self.W2**2).sum() | |
128 | |
129 | |
130 | |
131 def negative_log_likelihood(self, y): | |
132 """Return the mean of the negative log-likelihood of the prediction | |
133 of this model under a given target distribution. | |
134 | |
135 .. math:: | |
136 | |
137 \frac{1}{|\mathcal{D}|}\mathcal{L} (\theta=\{W,b\}, \mathcal{D}) = | |
138 \frac{1}{|\mathcal{D}|}\sum_{i=0}^{|\mathcal{D}|} \log(P(Y=y^{(i)}|x^{(i)}, W,b)) \\ | |
139 \ell (\theta=\{W,b\}, \mathcal{D}) | |
140 | |
141 | |
142 :param y: corresponds to a vector that gives for each example the | |
143 :correct label | |
144 """ | |
145 return -T.mean(T.log(self.p_y_given_x)[T.arange(y.shape[0]),y]) | |
146 | |
147 | |
148 | |
149 | |
150 def errors(self, y): | |
151 """Return a float representing the number of errors in the minibatch | |
152 over the total number of examples of the minibatch | |
153 """ | |
154 | |
155 # check if y has same dimension of y_pred | |
156 if y.ndim != self.y_pred.ndim: | |
157 raise TypeError('y should have the same shape as self.y_pred', | |
158 ('y', target.type, 'y_pred', self.y_pred.type)) | |
159 # check if y is of the correct datatype | |
160 if y.dtype.startswith('int'): | |
161 # the T.neq operator returns a vector of 0s and 1s, where 1 | |
162 # represents a mistake in prediction | |
163 return T.mean(T.neq(self.y_pred, y)) | |
164 else: | |
165 raise NotImplementedError() | |
166 | |
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167 def mlp_get_nist_error(model_name='/u/mullerx/ift6266h10_sandbox_db/xvm_final_lr1_p073/8/best_model.npy.npz', |
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168 data_set=0): |
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169 |
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170 |
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171 |
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172 # allocate symbolic variables for the data |
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173 x = T.fmatrix() # the data is presented as rasterized images |
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174 y = T.lvector() # the labels are presented as 1D vector of |
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175 # [long int] labels |
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176 |
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177 # load the data set and create an mlp based on the dimensions of the model |
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178 model=numpy.load(model_name) |
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179 W1=model['W1'] |
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180 W2=model['W2'] |
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181 b1=model['b1'] |
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182 b2=model['b2'] |
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183 nb_hidden=b1.shape[0] |
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184 input_dim=W1.shape[0] |
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185 nb_targets=b2.shape[0] |
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186 learning_rate=0.1 |
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187 |
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188 |
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189 if data_set==0: |
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190 dataset=datasets.nist_all() |
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191 elif data_set==1: |
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192 dataset=datasets.nist_P07() |
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193 |
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194 |
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195 classifier = MLP( input=x,\ |
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196 n_in=input_dim,\ |
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197 n_hidden=nb_hidden,\ |
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198 n_out=nb_targets, |
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199 learning_rate=learning_rate) |
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200 |
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201 |
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202 #overwrite weights with weigths from model |
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203 classifier.W1.value=W1 |
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204 classifier.W2.value=W2 |
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205 classifier.b1.value=b1 |
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206 classifier.b2.value=b2 |
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207 |
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208 |
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209 cost = classifier.negative_log_likelihood(y) \ |
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210 + 0.0 * classifier.L1 \ |
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211 + 0.0 * classifier.L2_sqr |
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212 |
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213 # compiling a theano function that computes the mistakes that are made by |
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214 # the model on a minibatch |
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215 test_model = theano.function([x,y], classifier.errors(y)) |
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216 |
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217 |
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218 |
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219 #get the test error |
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220 #use a batch size of 1 so we can get the sub-class error |
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221 #without messing with matrices (will be upgraded later) |
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222 test_score=0 |
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223 temp=0 |
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224 for xt,yt in dataset.test(20): |
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225 test_score += test_model(xt,yt) |
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226 temp = temp+1 |
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227 test_score /= temp |
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228 |
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229 |
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230 return test_score*100 |
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231 |
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232 |
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233 |
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234 |
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235 |
110 | 236 |
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237 def mlp_full_nist( verbose = 1,\ |
145
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238 adaptive_lr = 0,\ |
322 | 239 data_set=0,\ |
110 | 240 learning_rate=0.01,\ |
241 L1_reg = 0.00,\ | |
242 L2_reg = 0.0001,\ | |
243 nb_max_exemples=1000000,\ | |
244 batch_size=20,\ | |
322 | 245 nb_hidden = 30,\ |
212
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246 nb_targets = 62, |
338
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247 tau=1e6,\ |
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248 lr_t2_factor=0.5,\ |
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249 init_model=0,\ |
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250 channel=0): |
110 | 251 |
252 | |
338
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253 if channel!=0: |
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254 channel.save() |
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255 configuration = [learning_rate,nb_max_exemples,nb_hidden,adaptive_lr] |
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256 |
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257 #save initial learning rate if classical adaptive lr is used |
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258 initial_lr=learning_rate |
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259 max_div_count=1000 |
323 | 260 |
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261 |
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262 total_validation_error_list = [] |
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263 total_train_error_list = [] |
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264 learning_rate_list=[] |
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265 best_training_error=float('inf'); |
323 | 266 divergence_flag_list=[] |
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267 |
322 | 268 if data_set==0: |
269 dataset=datasets.nist_all() | |
323 | 270 elif data_set==1: |
271 dataset=datasets.nist_P07() | |
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272 elif data_set==2: |
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273 dataset=datasets.PNIST07() |
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274 |
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275 |
110 | 276 |
277 | |
278 ishape = (32,32) # this is the size of NIST images | |
279 | |
280 # allocate symbolic variables for the data | |
281 x = T.fmatrix() # the data is presented as rasterized images | |
282 y = T.lvector() # the labels are presented as 1D vector of | |
283 # [long int] labels | |
284 | |
322 | 285 |
110 | 286 # construct the logistic regression class |
322 | 287 classifier = MLP( input=x,\ |
110 | 288 n_in=32*32,\ |
289 n_hidden=nb_hidden,\ | |
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290 n_out=nb_targets, |
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291 learning_rate=learning_rate) |
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292 |
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293 |
338
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294 # check if we want to initialise the weights with a previously calculated model |
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295 # dimensions must be consistent between old model and current configuration!!!!!! (nb_hidden and nb_targets) |
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296 if init_model!=0: |
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297 old_model=numpy.load(init_model) |
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298 classifier.W1.value=old_model['W1'] |
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299 classifier.W2.value=old_model['W2'] |
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300 classifier.b1.value=old_model['b1'] |
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301 classifier.b2.value=old_model['b2'] |
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302 |
110 | 303 |
304 # the cost we minimize during training is the negative log likelihood of | |
305 # the model plus the regularization terms (L1 and L2); cost is expressed | |
306 # here symbolically | |
307 cost = classifier.negative_log_likelihood(y) \ | |
308 + L1_reg * classifier.L1 \ | |
309 + L2_reg * classifier.L2_sqr | |
310 | |
311 # compiling a theano function that computes the mistakes that are made by | |
312 # the model on a minibatch | |
313 test_model = theano.function([x,y], classifier.errors(y)) | |
314 | |
315 # compute the gradient of cost with respect to theta = (W1, b1, W2, b2) | |
316 g_W1 = T.grad(cost, classifier.W1) | |
317 g_b1 = T.grad(cost, classifier.b1) | |
318 g_W2 = T.grad(cost, classifier.W2) | |
319 g_b2 = T.grad(cost, classifier.b2) | |
320 | |
321 # specify how to update the parameters of the model as a dictionary | |
322 updates = \ | |
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323 { classifier.W1: classifier.W1 - classifier.lr*g_W1 \ |
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324 , classifier.b1: classifier.b1 - classifier.lr*g_b1 \ |
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325 , classifier.W2: classifier.W2 - classifier.lr*g_W2 \ |
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326 , classifier.b2: classifier.b2 - classifier.lr*g_b2 } |
110 | 327 |
328 # compiling a theano function `train_model` that returns the cost, but in | |
329 # the same time updates the parameter of the model based on the rules | |
330 # defined in `updates` | |
331 train_model = theano.function([x, y], cost, updates = updates ) | |
322 | 332 |
333 | |
334 | |
110 | 335 |
336 | |
337 | |
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338 |
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339 |
110 | 340 |
341 #conditions for stopping the adaptation: | |
323 | 342 #1) we have reached nb_max_exemples (this is rounded up to be a multiple of the train size so we always do at least 1 epoch) |
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343 #2) validation error is going up twice in a row(probable overfitting) |
110 | 344 |
345 # This means we no longer stop on slow convergence as low learning rates stopped | |
323 | 346 # too fast but instead we will wait for the valid error going up 3 times in a row |
347 # We save the curb of the validation error so we can always go back to check on it | |
348 # and we save the absolute best model anyway, so we might as well explore | |
349 # a bit when diverging | |
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350 |
323 | 351 #approximate number of samples in the nist training set |
322 | 352 #this is just to have a validation frequency |
323 | 353 #roughly proportionnal to the original nist training set |
322 | 354 n_minibatches = 650000/batch_size |
355 | |
356 | |
323 | 357 patience =2*nb_max_exemples/batch_size #in units of minibatch |
110 | 358 validation_frequency = n_minibatches/4 |
359 | |
360 | |
361 | |
362 | |
322 | 363 |
110 | 364 best_validation_loss = float('inf') |
365 best_iter = 0 | |
366 test_score = 0. | |
367 start_time = time.clock() | |
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368 time_n=0 #in unit of exemples |
322 | 369 minibatch_index=0 |
370 epoch=0 | |
371 temp=0 | |
323 | 372 divergence_flag=0 |
322 | 373 |
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374 |
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375 |
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376 |
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377 print 'starting training' |
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378 sys.stdout.flush() |
322 | 379 while(minibatch_index*batch_size<nb_max_exemples): |
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380 |
322 | 381 for x, y in dataset.train(batch_size): |
110 | 382 |
323 | 383 #if we are using the classic learning rate deacay, adjust it before training of current mini-batch |
322 | 384 if adaptive_lr==2: |
385 classifier.lr.value = tau*initial_lr/(tau+time_n) | |
386 | |
387 | |
388 #train model | |
389 cost_ij = train_model(x,y) | |
390 | |
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391 if (minibatch_index) % validation_frequency == 0: |
322 | 392 #save the current learning rate |
393 learning_rate_list.append(classifier.lr.value) | |
323 | 394 divergence_flag_list.append(divergence_flag) |
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395 |
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396 |
322 | 397 |
398 # compute the validation error | |
399 this_validation_loss = 0. | |
400 temp=0 | |
401 for xv,yv in dataset.valid(1): | |
402 # sum up the errors for each minibatch | |
323 | 403 this_validation_loss += test_model(xv,yv) |
322 | 404 temp=temp+1 |
405 # get the average by dividing with the number of minibatches | |
406 this_validation_loss /= temp | |
407 #save the validation loss | |
408 total_validation_error_list.append(this_validation_loss) | |
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409 |
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410 print(('epoch %i, minibatch %i, learning rate %f current validation error %f ') % |
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411 (epoch, minibatch_index+1,classifier.lr.value, |
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412 this_validation_loss*100.)) |
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413 sys.stdout.flush() |
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414 |
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415 #save temp results to check during training |
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416 numpy.savez('temp_results.npy',config=configuration,total_validation_error_list=total_validation_error_list,\ |
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417 learning_rate_list=learning_rate_list, divergence_flag_list=divergence_flag_list) |
322 | 418 |
419 # if we got the best validation score until now | |
420 if this_validation_loss < best_validation_loss: | |
421 # save best validation score and iteration number | |
422 best_validation_loss = this_validation_loss | |
423 best_iter = minibatch_index | |
323 | 424 #reset divergence flag |
425 divergence_flag=0 | |
426 | |
427 #save the best model. Overwrite the current saved best model so | |
428 #we only keep the best | |
429 numpy.savez('best_model.npy', config=configuration, W1=classifier.W1.value, W2=classifier.W2.value, b1=classifier.b1.value,\ | |
430 b2=classifier.b2.value, minibatch_index=minibatch_index) | |
431 | |
322 | 432 # test it on the test set |
433 test_score = 0. | |
434 temp =0 | |
435 for xt,yt in dataset.test(batch_size): | |
436 test_score += test_model(xt,yt) | |
437 temp = temp+1 | |
438 test_score /= temp | |
355
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439 |
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440 print(('epoch %i, minibatch %i, test error of best ' |
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441 'model %f %%') % |
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442 (epoch, minibatch_index+1, |
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443 test_score*100.)) |
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444 sys.stdout.flush() |
322 | 445 |
446 # if the validation error is going up, we are overfitting (or oscillating) | |
323 | 447 # check if we are allowed to continue and if we will adjust the learning rate |
322 | 448 elif this_validation_loss >= best_validation_loss: |
323 | 449 |
450 | |
451 # In non-classic learning rate decay, we modify the weight only when | |
452 # validation error is going up | |
453 if adaptive_lr==1: | |
454 classifier.lr.value=classifier.lr.value*lr_t2_factor | |
455 | |
456 | |
457 #cap the patience so we are allowed to diverge max_div_count times | |
458 #if we are going up max_div_count in a row, we will stop immediatelty by modifying the patience | |
459 divergence_flag = divergence_flag +1 | |
460 | |
461 | |
322 | 462 #calculate the test error at this point and exit |
463 # test it on the test set | |
464 test_score = 0. | |
465 temp=0 | |
466 for xt,yt in dataset.test(batch_size): | |
467 test_score += test_model(xt,yt) | |
468 temp=temp+1 | |
469 test_score /= temp | |
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470 |
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471 print ' validation error is going up, possibly stopping soon' |
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472 print((' epoch %i, minibatch %i, test error of best ' |
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473 'model %f %%') % |
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474 (epoch, minibatch_index+1, |
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475 test_score*100.)) |
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476 sys.stdout.flush() |
322 | 477 |
478 | |
479 | |
323 | 480 # check early stop condition |
481 if divergence_flag==max_div_count: | |
482 minibatch_index=nb_max_exemples | |
483 print 'we have diverged, early stopping kicks in' | |
484 break | |
485 | |
486 #check if we have seen enough exemples | |
487 #force one epoch at least | |
488 if epoch>0 and minibatch_index*batch_size>nb_max_exemples: | |
322 | 489 break |
338
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490 |
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491 |
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492 |
322 | 493 |
494 | |
495 time_n= time_n + batch_size | |
323 | 496 minibatch_index = minibatch_index + 1 |
497 | |
498 # we have finished looping through the training set | |
322 | 499 epoch = epoch+1 |
110 | 500 end_time = time.clock() |
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501 |
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502 print(('Optimization complete. Best validation score of %f %% ' |
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503 'obtained at iteration %i, with test performance %f %%') % |
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504 (best_validation_loss * 100., best_iter, test_score*100.)) |
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505 print ('The code ran for %f minutes' % ((end_time-start_time)/60.)) |
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506 print minibatch_index |
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507 sys.stdout.flush() |
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508 |
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509 #save the model and the weights |
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510 numpy.savez('model.npy', config=configuration, W1=classifier.W1.value,W2=classifier.W2.value, b1=classifier.b1.value,b2=classifier.b2.value) |
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511 numpy.savez('results.npy',config=configuration,total_train_error_list=total_train_error_list,total_validation_error_list=total_validation_error_list,\ |
323 | 512 learning_rate_list=learning_rate_list, divergence_flag_list=divergence_flag_list) |
143
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513 |
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514 return (best_training_error*100.0,best_validation_loss * 100.,test_score*100.,best_iter*batch_size,(end_time-start_time)/60) |
110 | 515 |
516 | |
517 if __name__ == '__main__': | |
518 mlp_full_mnist() | |
519 | |
520 def jobman_mlp_full_nist(state,channel): | |
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521 (train_error,validation_error,test_error,nb_exemples,time)=mlp_full_nist(learning_rate=state.learning_rate,\ |
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522 nb_max_exemples=state.nb_max_exemples,\ |
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523 nb_hidden=state.nb_hidden,\ |
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524 adaptive_lr=state.adaptive_lr,\ |
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525 tau=state.tau,\ |
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526 verbose = state.verbose,\ |
324 | 527 lr_t2_factor=state.lr_t2_factor, |
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528 data_set=state.data_set, |
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529 channel=channel) |
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530 state.train_error=train_error |
110 | 531 state.validation_error=validation_error |
532 state.test_error=test_error | |
533 state.nb_exemples=nb_exemples | |
534 state.time=time | |
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535 pylearn.version.record_versions(state,[theano,ift6266,pylearn]) |
110 | 536 return channel.COMPLETE |
537 | |
538 |