How use TPU in google colab

Question

Google colab brings TPUs in the Runtime Accelerator. I found an example, How to use TPU in Official Tensorflow github. But the example not worked on google-colaboratory. It stuck on following line:

tf.contrib.tpu.keras_to_tpu_model(model, strategy=strategy)

When I print available devices on colab it return [] for TPU accelerator. Does anyone knows how to use TPU on colab?

Answer 1

Here's a Colab-specific TPU example: https://colab.research.google.com/github/tensorflow/tpu/blob/master/tools/colab/shakespeare_with_tpu_and_keras.ipynb

The key lines are those to connect to the TPU itself:

# This address identifies the TPU we'll use when configuring TensorFlow.
TPU_WORKER = 'grpc://' + os.environ['COLAB_TPU_ADDR']

...

tpu_model = tf.contrib.tpu.keras_to_tpu_model(
training_model,
strategy=tf.contrib.tpu.TPUDistributionStrategy(
    tf.contrib.cluster_resolver.TPUClusterResolver(TPU_WORKER)))

(Unlike a GPU, use of the TPU requires an explicit connection to the TPU worker. So, you'll need to tweak your training and inference definition in order to observe a speedup.)