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板凳
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楼主 |
发表于 2015-12-27 10:42:56
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import tensorflow as tf
import numpy as np
import input_data
def init_weights(shape):
return tf.Variable(tf.random_normal(shape, stddev=0.01))
def model(X, w):
return tf.matmul(X, w) # notice we use the same model as linear regression, this is because there is a baked in cost function which performs softmax and cross entropy
mnist = input_data.read_data_sets("MNIST_data/", one_hot=True)
trX, trY, teX, teY = mnist.train.images, mnist.train.labels, mnist.test.images, mnist.test.labels
X = tf.placeholder("float", [None, 784]) # create symbolic variables
Y = tf.placeholder("float", [None, 10])
w = init_weights([784, 10]) # like in linear regression, we need a shared variable weight matrix for logistic regression
py_x = model(X, w)
cost = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(py_x, Y)) # compute mean cross entropy (softmax is applied internally)
train_op = tf.train.GradientDescentOptimizer(0.05).minimize(cost) # construct optimizer
predict_op = tf.argmax(py_x, 1) # at predict time, evaluate the argmax of the logistic regression
sess = tf.Session()
init = tf.initialize_all_variables()
sess.run(init)
for i in range(100):
for start, end in zip(range(0, len(trX), 128), range(128, len(trX), 128)):
sess.run(train_op, feed_dict={X: trX[start:end], Y: trY[start:end]})
print i, np.mean(np.argmax(teY, axis=1) ==
sess.run(predict_op, feed_dict={X: teX, Y: teY})) |
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