Perfectly shuffle files for better randomization.

[copybara-service]

Perfectly shuffle files for better randomization.

With a limited buffer size, you are likely to pick the earlier shards
irrespective of the seed in the initial cycle_length draws.

import tensorflow as tf

def sample(seed, buffer_size, cycle_length=16, num_files=10155):
dataset = tf.data.Dataset.range(num_files)

dataset = dataset.shuffle(buffer_size=buffer_size, seed=seed)

dataset = dataset.interleave(
lambda x: tf.data.Dataset.from_tensors(x).repeat(1),
cycle_...

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