Tensorflow has an example tutorial about classifying CIFAR-10. On the tutorial the average cross entropy loss across the batch is minimized.
def loss(logits, labels): """Add L2Loss to all the trainable variables. Add summary for for "Loss" and "Loss/avg". Args: logits: Logits from inference(). labels: Labels from distorted_inputs or inputs(). 1-D tensor of shape [batch_size] Returns: Loss tensor of type float. """ # Calculate the average cross entropy loss across the batch. labels = tf.cast(labels, tf.int64) cross_entropy = tf.nn.sparse_softmax_cross_entropy_with_logits( logits, labels, name='cross_entropy_per_example') cross_entropy_mean = tf.reduce_mean(cross_entropy, name='cross_entropy') tf.add_to_collection('losses', cross_entropy_mean) # The total loss is defined as the cross entropy loss plus all of the weight # decay terms (L2 loss). return tf.add_n(tf.get_collection('losses'), name='total_loss')
See cifar10.py, line 267.
Why doesn't it minimize the sum across the batch instead? Does it make a difference? I don't understand how this would affect the backprop calculation.