Interpreting the FLOPs profile result of tensorflow

Question

I want to profile the FLOPs of a very simple neural network model, which is used to classify the MNIST dataset, and the batch size is 128. As I followed the official tutorials, I got the result of the following model, but I cannot understand some parts of the output.

w1 = tf.Variable(tf.random_uniform([784, 15]), name='w1')
w2 = tf.Variable(tf.random_uniform([15, 10]), name='w2')
b1 = tf.Variable(tf.zeros([15, ]), name='b1')
b2 = tf.Variable(tf.zeros([10, ]), name='b2')

hidden_layer = tf.add(tf.matmul(images_iter, w1), b1)
logits = tf.add(tf.matmul(hidden_layer, w2), b2)

loss_op = tf.reduce_sum(\
    tf.nn.softmax_cross_entropy_with_logits(logits=logits, 
                                            labels=labels_iter))
opetimizer = tf.train.AdamOptimizer(learning_rate=0.01)
train_op = opetimizer.minimize(loss_op)

The images_iter and the labels_iter are the iterators of tf.data, which are similar to the placeholder.

tf.profiler.profile(
    tf.get_default_graph(),
    options=tf.profiler.ProfileOptionBuilder.float_operation())

I used this code, which equals to scope -min_float_ops 1 -select float_ops -account_displayed_op_only in tfprof comments line tool, to profile the FLOPs and got the below result.

Profile:
node name | # float_ops
_TFProfRoot (--/23.83k flops)
  random_uniform (11.76k/23.52k flops)
    random_uniform/mul (11.76k/11.76k flops)
    random_uniform/sub (1/1 flops)
  random_uniform_1 (150/301 flops)
    random_uniform_1/mul (150/150 flops)
    random_uniform_1/sub (1/1 flops)
  Adam/mul (1/1 flops)
  Adam/mul_1 (1/1 flops)
  softmax_cross_entropy_with_logits_sg/Sub (1/1 flops)
  softmax_cross_entropy_with_logits_sg/Sub_1 (1/1 flops)
  softmax_cross_entropy_with_logits_sg/Sub_2 (1/1 flops)

My questions are

1. What do the numbers in the parentheses mean? For example, random_uniform_1 (150/301 flops), what are 150 and 301?
2. Why is the first number in the parentheses of _TFProfRoot "--"?
3. Why are the flops of Adam/mul and softmax_cross_entropy_with_logits_sg/Sub 1?

I know it is discouraging to read a question so long, but a desperate boy who cannot find relating information from the official document needs your guys to help.

Answer 1

I'll give it a try:

(1) From this example, looks like the first number is the "self" flops, the second number means the "total" flops under the naming scope. For example: for the 3 nodes respectively named random_uniform (if there is such a node), random_uniform/mul, random_uniform/sub, they respectively take 11.76k, 11.76k, and 1 flops, and in total 23.52k flops.

For another example: 23.83k = 23.52k + 300.

Does this make sense?

(2) The root node is a "virtual" top-level node added by the profiler, which doesn't have a "self" flops , or in other words, it has zero self flops.

(3) Not sure why it is 1. It would help if you can print the GraphDef and find out what this node really is, with print(sess.graph_def)

Hope this helps.