Tutorial中的TensorFlow错误

Question

我敢问？在这一点上,这是一项新技术,我无法找到解决这个看似简单错误的方法.我正在浏览的教程可以在这里找到 - http://www.tensorflow.org/tutorials/mnist/pros/index.html#deep-mnist-for-experts

我将所有代码复制并粘贴到IPython Notebook中,并在最后一段代码中出现错误.

# To train and evaluate it we will use code that is nearly identical to that for the simple one layer SoftMax network above.
# The differences are that: we will replace the steepest gradient descent optimizer with the more sophisticated ADAM optimizer.

cross_entropy = -tf.reduce_sum(y_*tf.log(y_conv))
train_step = tf.train.AdamOptimizer(1e-4).minimize(cross_entropy)
correct_prediction = tf.equal(tf.argmax(y_conv,1), tf.argmax(y_,1))
accuracy = tf.reduce_mean(tf.cast(correct_prediction, "float"))
sess.run(tf.initialize_all_variables())
for i in range(20000):
    batch = mnist.train.next_batch(50)
    if i%100 == 0:
        train_accuracy = accuracy.eval(feed_dict={x:batch[0], y_: batch[1], keep_prob: 1.0})
    print "step %d, training accuracy %g"%(i, train_accuracy)
    train_step.run(feed_dict={x: batch[0], y_: batch[1], keep_prob: 0.5})

print "test accuracy %g"%accuracy.eval(feed_dict={
    x: mnist.test.images, y_: mnist.test.labels, keep_prob: 1.0})

运行此代码后,我收到此错误.

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-46-a5d1ab5c0ca8> in <module>()
     15 
     16 print "test accuracy %g"%accuracy.eval(feed_dict={
---> 17     x: mnist.test.images, y_: mnist.test.labels, keep_prob: 1.0})

/root/anaconda/lib/python2.7/site-packages/tensorflow/python/framework/ops.pyc in eval(self, feed_dict, session)
    403 
    404     """
--> 405     return _eval_using_default_session(self, feed_dict, self.graph, session)
    406 
    407 

/root/anaconda/lib/python2.7/site-packages/tensorflow/python/framework/ops.pyc in _eval_using_default_session(tensors, feed_dict, graph, session)
   2712     session = get_default_session()
   2713     if session is None:
-> 2714       raise ValueError("Cannot evaluate tensor using eval(): No default "
   2715                        "session is registered. Use 'with "
   2716                        "DefaultSession(sess)' or pass an explicit session to "

ValueError: Cannot evaluate tensor using eval(): No default session is registered. Use 'with DefaultSession(sess)' or pass an explicit session to eval(session=sess)

我以为我可能需要通过conda install https://storage.googleapis.com/tensorflow/linux/cpu/tensorflow-0.5.0-cp27-none-linux_x86_64.whl安装或重新安装TensorFlow,但conda甚至不知道如何安装它.

有没有人知道如何解决这个错误？

Answer 1

我想到了.正如您在值错误中看到的那样,它说的No default session is registered. Use 'with DefaultSession(sess)' or pass an explicit session to eval(session=sess)是我提出的答案是将显式会话传递给eval,就像它说的那样.这是我做出改变的地方.

if i%100 == 0:
        train_accuracy = accuracy.eval(session=sess, feed_dict={x:batch[0], y_: batch[1], keep_prob: 1.0})

和

train_step.run(session=sess, feed_dict={x: batch[0], y_: batch[1], keep_prob: 0.5})

现在代码工作正常.