4-4-1-8. Quiz: TensorFlow Cross Entropy

Cross Entropy in TensorFlow

As with the softmax function, TensorFlow has a function to do the cross entropy calculations for us.

Let’s take what you learned from the video and create a cross entropy function in TensorFlow. To create a cross entropy function in TensorFlow, you’ll need to use two new functions:

Reduce Sum

x = tf.reduce_sum([1, 2, 3, 4, 5])  # 15

The tf.reduce_sum() function takes an array of numbers and sums them together.

Natural Log

x = tf.log(100.0)  # 4.60517

This function does exactly what you would expect it to do. tf.log() takes the natural log of a number.

Quiz

Print the cross entropy using softmax_data and one_hot_encod_label.

(Alternative link for users in China.)

quiz.py

# Solution is available in the other "solution.py" tab
import tensorflow as tf

softmax_data = [0.7, 0.2, 0.1]
one_hot_data = [1.0, 0.0, 0.0]

softmax = tf.placeholder(tf.float32)
one_hot = tf.placeholder(tf.float32)

# TODO: Print cross entropy from session

solution.py

# Quiz Solution
# Note: You can't run code in this tab
import tensorflow as tf

softmax_data = [0.7, 0.2, 0.1]
one_hot_data = [1.0, 0.0, 0.0]

softmax = tf.placeholder(tf.float32)
one_hot = tf.placeholder(tf.float32)

# ToDo: Print cross entropy from session
cross_entropy = -tf.reduce_sum(tf.multiply(one_hot, tf.log(softmax)))

with tf.Session() as sess:
    print(sess.run(cross_entropy, feed_dict={softmax: softmax_data, one_hot: one_hot_data}))
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