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+# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Sliding dataset transformations."""
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from tensorflow.python.data.ops import dataset_ops
+from tensorflow.python.data.util import nest
+from tensorflow.python.data.util import sparse
+from tensorflow.python.framework import dtypes
+from tensorflow.python.framework import ops
+from tensorflow.python.framework import tensor_shape
+from tensorflow.python.ops import gen_dataset_ops
+
+
+class _SlideDataset(dataset_ops.Dataset):
+ """A `Dataset` that passes a sliding window over its input."""
+
+ def __init__(self, input_dataset, window_size, stride=1):
+ """See `sliding_window_batch` for details."""
+ super(_SlideDataset, self).__init__()
+ self._input_dataset = input_dataset
+ self._window_size = ops.convert_to_tensor(
+ window_size, dtype=dtypes.int64, name="window_size")
+ self._stride = ops.convert_to_tensor(
+ stride, dtype=dtypes.int64, name="stride")
+
+ def _as_variant_tensor(self):
+ return gen_dataset_ops.slide_dataset(
+ self._input_dataset._as_variant_tensor(), # pylint: disable=protected-access
+ window_size=self._window_size,
+ stride=self._stride,
+ output_shapes=nest.flatten(
+ sparse.as_dense_shapes(self.output_shapes, self.output_classes)),
+ output_types=nest.flatten(
+ sparse.as_dense_types(self.output_types, self.output_classes)))
+
+ @property
+ def output_classes(self):
+ return self._input_dataset.output_classes
+
+ @property
+ def output_shapes(self):
+ input_shapes = self._input_dataset.output_shapes
+ return nest.pack_sequence_as(input_shapes, [
+ tensor_shape.vector(None).concatenate(s)
+ for s in nest.flatten(self._input_dataset.output_shapes)
+ ])
+
+ @property
+ def output_types(self):
+ return self._input_dataset.output_types
+
+
+def sliding_window_batch(window_size, stride=1):
+ """A sliding window with size of `window_size` and step of `stride`.
+
+ This transformation passes a sliding window over this dataset. The
+ window size is `window_size` and step size is `stride`. If the left
+ elements cannot fill up the sliding window, this transformation will
+ drop the final smaller element. For example:
+
+ ```python
+ # NOTE: The following examples use `{ ... }` to represent the
+ # contents of a dataset.
+ a = { [1], [2], [3], [4], [5], [6] }
+
+ a.apply(tf.contrib.data.sliding_window_batch(window_size=3, stride=2)) ==
+ {
+ [[1], [2], [3]],
+ [[3], [4], [5]],
+ }
+ ```
+
+ Args:
+ window_size: A `tf.int64` scalar `tf.Tensor`, representing the number of
+ elements in the sliding window.
+ stride: (Optional.) A `tf.int64` scalar `tf.Tensor`, representing the
+ steps moving the sliding window forward for one iteration. The default
+ is `1`. It must be in `[1, window_size)`.
+
+ Returns:
+ A `Dataset` transformation function, which can be passed to
+ @{tf.data.Dataset.apply}.
+ """
+ def _apply_fn(dataset):
+ return _SlideDataset(dataset, window_size, stride)
+
+ return _apply_fn