Sliding window of a batch in Tensorflow using Dataset API

Answering both the original post and Answering @cabbage_soup's comment to vijay's response:

To achieve an efficient sliding window the following code can be used.

data = data.window(size=batch_size, stride=1, shift=1, drop_remainder=True ) data = data.interleave( lambda *window: tf.data.Dataset.zip(tuple([w.batch(batch_size) for w in window])), cycle_length=10, block_length=10 ,num_parallel_calls=4 )

Interleave is used instead of flat_map as it allows processing to be done in parallel during this window transformation.

Refer to the documentation to choose values for cycle_length, block_length and num_parallel_calls that are appropriate for your hardware and data.

Can be achieved using sliding window batch operation for tf.data.Dataset:

Example:

from tensorflow.contrib.data.python.ops import sliding

imgs = tf.constant(['img0','img1', 'img2','img3', 'img4','img5', 'img6', 'img7'])
labels = tf.constant([0, 0, 0, 1, 1, 1, 0, 0])

# create TensorFlow Dataset object
data = tf.data.Dataset.from_tensor_slices((imgs, labels))

# sliding window batch
window = 4
stride = 1
data = data.apply(sliding.sliding_window_batch(window, stride))

# create TensorFlow Iterator object
iterator =  tf.data.Iterator.from_structure(data.output_types,data.output_shapes)
next_element = iterator.get_next()

# create initialization ops 
init_op = iterator.make_initializer(data)

with tf.Session() as sess:
   # initialize the iterator on the data
   sess.run(init_op)
   while True:
      try:
         elem = sess.run(next_element)
         print(elem)
      except tf.errors.OutOfRangeError:
         print("End of dataset.")
         break

Output:

 (array([b'img0', b'img1', b'img2', b'img3'], dtype=object), array([0, 0, 0, 1], dtype=int32))
 (array([b'img1', b'img2', b'img3', b'img4'], dtype=object), array([0, 0, 1, 1], dtype=int32))
 (array([b'img2', b'img3', b'img4', b'img5'], dtype=object), array([0, 1, 1, 1], dtype=int32))
 (array([b'img3', b'img4', b'img5', b'img6'], dtype=object), array([1, 1, 1, 0], dtype=int32))
 (array([b'img4', b'img5', b'img6', b'img7'], dtype=object), array([1, 1, 0, 0], dtype=int32))

With tensorflow >= 2.1, it is possible to use the window(), flat_map() and batch() functions to get desired results.

Example:

## Sample data list
x_train = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90]

## Constants
batch_size = 10
shift_window_size = 1

## Create tensor slices
train_d = tf.data.Dataset.from_tensor_slices(x_train)

## Create dataset of datasets with a specific window and shift size
train_d = train_d.window(size=batch_size,shift=shift_window_size, drop_remainder=True)

## Define a function to create a flat dataset from the dataset of datasets
def create_seqeunce_ds(chunk):
    return chunk.batch(batch_size, drop_remainder=True)

## Create a dataset using a map with mapping function defined above
train_d = train_d.flat_map(create_seqeunce_ds)

## Check the contents
for item in train_d:
    print(item)

Output:

tf.Tensor([ 1  2  3  4  5  6  7  8  9 10], shape=(10,), dtype=int32)
tf.Tensor([ 2  3  4  5  6  7  8  9 10 20], shape=(10,), dtype=int32)
tf.Tensor([ 3  4  5  6  7  8  9 10 20 30], shape=(10,), dtype=int32)
tf.Tensor([ 4  5  6  7  8  9 10 20 30 40], shape=(10,), dtype=int32)
tf.Tensor([ 5  6  7  8  9 10 20 30 40 50], shape=(10,), dtype=int32)
tf.Tensor([ 6  7  8  9 10 20 30 40 50 60], shape=(10,), dtype=int32)
tf.Tensor([ 7  8  9 10 20 30 40 50 60 70], shape=(10,), dtype=int32)
tf.Tensor([ 8  9 10 20 30 40 50 60 70 80], shape=(10,), dtype=int32)
tf.Tensor([ 9 10 20 30 40 50 60 70 80 90], shape=(10,), dtype=int32)

More details can be found here: TF Data Guide