Showing posts with label: tensor_flow. Show all posts.

Batch Normalization with TensorFlow

Tuesday 13 February 2018

I was trying to use batch normalization in order to improve the accuracy of my CIFAR classifier with tf.layers.batch_normalization, and it seemed to have little to no effect. According to this StackOverflow post you need to do something extra, which is not mentioned in the documentation, in order to get the batch normalization to work.

extra_update_ops = tf.get_collection(tf.GraphKeys.UPDATE_OPS)[train_op, extra_update_ops], ...)

The batch norm update operations are added to UPDATE_OPS collection, so you need to create that operation and then feed it into the session along with the training op. Before I had added the extra_update_ops the batch normalization was definitely not running, now it is, whether it helps or not remains to be seen.

Also make sure to use a training=[BOOLEAN | TENSOR] in the call to batch_normalization() to prevent it from being applied during evaluation. I use a placeholder and pass whether it is training or not in via the feed_dict:

training = tf.placeholder(dtype=tf.bool)

And then use this in my batch norm and dropout layers:


There were a few other things I had to do to get batch normalization to work properly:

  1. I had been using local response normalization, which apparently doesn't help that much. I removed those layers and replaced them with batch normalization layers.
  2. Remove the activation from the conv2d layers. I run the output through the batch normalize layers and then apply the relu.

Before I made these changes the model with the batch normalization didn't seem to be training at all, the accuracy was just going up and down right around the baseline of .10. After these changes it seems to be training properly now.

Labels: data_science, machine_learning, tensor_flow
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TensorFlow GPU Errors on Windows

Monday 12 February 2018

I have been loving TensorFlow lately and have installed tensorflow-gpu on my Windows 10 laptop. Given that the GPU on my laptop is not a really great one I have run into quite a few issues, most of which I have solved. My GPU is an Nvidia GeForce GT 750M with 2GB of RAM and I am running the latest release of tensorflow as of February 2018, with Python 3.6. 

If you are running into errors I would suggest you try these things in this order:

  1. Try reducing the batch size for training AND validation. I always use batches for training but would evaluate on the validation data all at once. By using batches for validation and averaging the results I am able to avoid most of the memory errors.
  2. If this doesn't work try to restrict the amount of GPU RAM available to tensorflow with config.gpu_options.per_process_gpu_memory_fraction = 0.7
    which restricts the amount  available to 70%. Note that I am unable to ever run the GPU with the memory fraction above 0.7
  3. If all else fails turn the GPU off and use the CPU: 
    config = tf.ConfigProto()
    config = tf.ConfigProto(device_count = {'GPU': 0})

The difference between using the CPU and the GPU is like night and day... With the CPU it takes all day to train through 20 epochs, with the GPU the same can be done in a few hours. I think the main roadblock with my GPU is the amount of RAM, which can easily be managed by controlling the batch size and the config settings above. Just remember to feed the config into the session.

Labels: python, data_science, machine_learning, tensor_flow
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