eager: Initial support for iteration over tf.contrib.data.Dataset objects.

TODO:
- Support function-valued operation attributes in eager
  (Required for MapDataset, FilterDataset etc. which encode the
  per-element computation in a TensorFlow function)
PiperOrigin-RevId: 168418250

tensorflow/contrib/eager/python/BUILD

@@ -2,13 +2,14 @@ licenses(["notice"])  # Apache 2.0
 
 package(default_visibility = ["//tensorflow:internal"])
 
-load("//tensorflow:tensorflow.bzl", "cuda_py_test")
+load("//tensorflow:tensorflow.bzl", "py_test", "cuda_py_test")
 
 py_library(
     name = "tfe",
     srcs = ["tfe.py"],
     srcs_version = "PY2AND3",
     deps = [
+        ":datasets",
         ":saver",
         "//tensorflow/python:framework_ops",
         "//tensorflow/python:util",
@@ -31,6 +32,34 @@ cuda_py_test(
     ],
 )
 
+py_library(
+    name = "datasets",
+    srcs = ["datasets.py"],
+    srcs_version = "PY2AND3",
+    visibility = ["//tensorflow:internal"],
+    deps = [
+        "//tensorflow/contrib/data/python/ops:dataset_ops",
+        "//tensorflow/contrib/data/python/util:nest",
+        "//tensorflow/python:dataset_ops_gen",
+        "//tensorflow/python:errors",
+        "//tensorflow/python:resource_variable_ops",
+        "//tensorflow/python/eager:context",
+    ],
+)
+
+py_test(
+    name = "datasets_test",
+    srcs = ["datasets_test.py"],
+    srcs_version = "PY2AND3",
+    deps = [
+        ":datasets",
+        "//tensorflow/contrib/data",
+        "//tensorflow/python:math_ops",
+        "//tensorflow/python/eager:test",
+        "//third_party/py/numpy",
+    ],
+)
+
 py_library(
     name = "saver",
     srcs = ["saver.py"],

tensorflow/contrib/eager/python/datasets.py

@@ -0,0 +1,96 @@
+# Copyright 2017 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.
+# ==============================================================================
+"""Support for tf.contrib.data when eager execution is enabled."""
+
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+import threading
+
+from tensorflow.contrib.data.python.util import nest
+from tensorflow.python.eager import context
+from tensorflow.python.framework import errors
+from tensorflow.python.ops import gen_dataset_ops
+from tensorflow.python.ops import resource_variable_ops
+
+_uid_counter = 0
+_uid_lock = threading.Lock()
+
+
+def _iterator_shared_name():
+  with _uid_lock:
+    global _uid_counter
+    uid = _uid_counter
+    _uid_counter += 1
+  return "eager_iterator_{}".format(uid)
+
+
+class Iterator(object):
+  """An iterator producing tf.Tensor objects from a tf.contrib.data.Dataset."""
+
+  def __init__(self, dataset):
+    """Creates a new iterator over the given dataset.
+
+    For example:
+    ```python
+    dataset = tf.contrib.data.Dataset.range(4)
+    for x in Iterator(dataset):
+      print(x)
+    ```
+
+    Args:
+      dataset: A `tf.contrib.data.Dataset` object.
+
+    Raises:
+      RuntimeError: When invoked without eager execution enabled.
+    """
+
+    if not context.in_eager_mode():
+      raise RuntimeError(
+          "{} objects only make sense when eager execution is enabled".format(
+              type(self)))
+    ds_variant = dataset.make_dataset_resource()
+    self._output_types = dataset.output_types
+    self._flat_output_types = nest.flatten(dataset.output_types)
+    self._flat_output_shapes = nest.flatten(dataset.output_shapes)
+    self._resource = gen_dataset_ops.iterator(
+        container="",
+        shared_name=_iterator_shared_name(),
+        output_types=self._flat_output_types,
+        output_shapes=self._flat_output_shapes)
+    gen_dataset_ops.make_iterator(ds_variant, self._resource)
+
+  def __del__(self):
+    if self._resource is not None:
+      resource_variable_ops.destroy_resource_op(self._resource)
+    self._resource = None
+
+  def __iter__(self):
+    return self
+
+  def __next__(self):  # For Python 3 compatibility
+    return self.next()
+
+  def next(self):
+    """Return the next tf.Tensor from the dataset."""
+    try:
+      ret = gen_dataset_ops.iterator_get_next(
+          self._resource,
+          output_types=self._flat_output_types,
+          output_shapes=self._flat_output_shapes)
+      return nest.pack_sequence_as(self._output_types, ret)
+    except errors.OutOfRangeError:
+      raise StopIteration

tensorflow/contrib/eager/python/datasets_test.py

@@ -0,0 +1,69 @@
+# Copyright 2017 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.
+# ==============================================================================
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+
+from tensorflow.contrib.data import Dataset
+from tensorflow.contrib.eager.python import datasets
+from tensorflow.python.eager import test
+from tensorflow.python.ops import math_ops
+
+
+class IteratorTest(test.TestCase):
+
+  def testBasic(self):
+    got = []
+    for t in datasets.Iterator(Dataset.range(4)):
+      got.append(t.numpy())
+    self.assertAllEqual([0, 1, 2, 3], got)
+
+  def testMultipleIteratorsOnTheSameDataset(self):
+    ds = Dataset.range(4)
+    it1 = datasets.Iterator(ds)
+    it2 = datasets.Iterator(ds)
+    got = [x.numpy() for x in it1]
+    self.assertAllEqual([0, 1, 2, 3], got)
+
+    got = [x.numpy() for x in it2]
+    self.assertAllEqual([0, 1, 2, 3], got)
+
+  def testNestedOutputs(self):
+    ds = Dataset.zip((Dataset.range(4), Dataset.zip((Dataset.range(4),
+                                                     Dataset.range(4)))))
+    total = 0
+    # The Iterator will return a nested structure of Tensor objects.
+    # Some funkiness to compare against simple integers.
+    for (i, x) in enumerate(datasets.Iterator(ds)):
+      want = (i, (i, i))
+      got = (x[0].numpy(), (x[1][0].numpy(), x[1][1].numpy()))
+      self.assertEqual(got, want)
+      total += 1
+    self.assertEqual(4, total)
+
+  def testMapAndFilter(self):
+    # TODO(ashankar): Address this
+    self.skipTest('Not working yet, requires function attribute support')
+
+    def even(x):
+      return math_ops.equal(math_ops.mod(x, 2), 0)
+
+    it = datasets.Iterator(Dataset.range(8).map(math_ops.square).filter(even))
+    got = [x.numpy() for x in it]
+    self.assertAllEqual([0, 4, 16, 36], got)
+
+
+if __name__ == '__main__':
+  test.main()