TensorFlow定义用于构造图形的类和函数

由 Carrie 创建, 最后一次修改 2017-09-18

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""用于构造图形的类和函数.""

# pylint: disable=g-bad-name from __future__ import absolute_import from __future__ import division from __future__ import print_function import collections from tensorflow.python.framework import dtypes from tensorflow.python.framework import ops from tensorflow.python.framework import tensor_util # pylint: disable=protected-access _TensorLike = ops._TensorLike _eval_using_default_session = ops._eval_using_default_session _override_helper = ops._override_helper # pylint: enable=protected-access class SparseTensor(_TensorLike): """Represents a sparse tensor. TensorFlow represents a sparse tensor as three separate dense tensors: `indices`, `values`, and `dense_shape`. In Python, the three tensors are collected into a `SparseTensor` class for ease of use. If you have separate `indices`, `values`, and `dense_shape` tensors, wrap them in a `SparseTensor` object before passing to the ops below. Concretely, the sparse tensor `SparseTensor(indices, values, dense_shape)` comprises the following components, where `N` and `ndims` are the number of values and number of dimensions in the `SparseTensor`, respectively: * `indices`: A 2-D int64 tensor of dense_shape `[N, ndims]`, which specifies the indices of the elements in the sparse tensor that contain nonzero values (elements are zero-indexed). For example, `indices=[[1,3], [2,4]]` specifies that the elements with indexes of [1,3] and [2,4] have nonzero values. * `values`: A 1-D tensor of any type and dense_shape `[N]`, which supplies the values for each element in `indices`. For example, given `indices=[[1,3], [2,4]]`, the parameter `values=[18, 3.6]` specifies that element [1,3] of the sparse tensor has a value of 18, and element [2,4] of the tensor has a value of 3.6. * `dense_shape`: A 1-D int64 tensor of dense_shape `[ndims]`, which specifies the dense_shape of the sparse tensor. Takes a list indicating the number of elements in each dimension. For example, `dense_shape=[3,6]` specifies a two-dimensional 3x6 tensor, `dense_shape=[2,3,4]` specifies a three-dimensional 2x3x4 tensor, and `dense_shape=[9]` specifies a one-dimensional tensor with 9 elements. The corresponding dense tensor satisfies: ```python dense.shape = dense_shape dense[tuple(indices[i])] = values[i] ``` By convention, `indices` should be sorted in row-major order (or equivalently lexicographic order on the tuples `indices[i]`). This is not enforced when `SparseTensor` objects are constructed, but most ops assume correct ordering. If the ordering of sparse tensor `st` is wrong, a fixed version can be obtained by calling `tf.sparse_reorder(st)`. Example: The sparse tensor ```python SparseTensor(indices=[[0, 0], [1, 2]], values=[1, 2], dense_shape=[3, 4]) ``` represents the dense tensor ```python [[1, 0, 0, 0] [0, 0, 2, 0] [0, 0, 0, 0]] ``` """ @classmethod def from_value(cls, sparse_tensor_value): if not (isinstance(sparse_tensor_value, SparseTensor) or isinstance(sparse_tensor_value, SparseTensorValue)): raise TypeError("Neither a SparseTensor nor SparseTensorValue: %s." % sparse_tensor_value) return SparseTensor( indices=sparse_tensor_value.indices, values=sparse_tensor_value.values, dense_shape=sparse_tensor_value.dense_shape) def __init__(self, indices, values, dense_shape): """Creates a `SparseTensor`. Args: indices: A 2-D int64 tensor of shape `[N, ndims]`. values: A 1-D tensor of any type and shape `[N]`. dense_shape: A 1-D int64 tensor of shape `[ndims]`. Returns: A `SparseTensor`. """ with ops.name_scope(None, "SparseTensor", [indices, values, dense_shape]): indices = ops.convert_to_tensor( indices, name="indices", dtype=dtypes.int64) # Always pass as_ref=True because we want to be able to update # values later if it is a VariableOp. # TODO(touts): Consider adding mutable_values() when 'values' # is a VariableOp and updating users of SparseTensor. values = ops.internal_convert_to_tensor( values, name="values", as_ref=True) dense_shape = ops.convert_to_tensor( dense_shape, name="dense_shape", dtype=dtypes.int64) self._indices = indices self._values = values self._dense_shape = dense_shape indices_shape = indices.get_shape().with_rank(2) values_shape = values.get_shape().with_rank(1) dense_shape_shape = dense_shape.get_shape().with_rank(1) # Assert number of rows in indices match the number of elements in values. indices_shape[0].merge_with(values_shape[0]) # Assert number of columns in indices matches the number of elements in # dense_shape. indices_shape[1].merge_with(dense_shape_shape[0]) def get_shape(self): """Get the `TensorShape` representing the shape of the dense tensor. Returns: A `TensorShape` object. """ return tensor_util.constant_value_as_shape(self._dense_shape) @property def indices(self): """The indices of non-zero values in the represented dense tensor. Returns: A 2-D Tensor of int64 with dense_shape `[N, ndims]`, where `N` is the number of non-zero values in the tensor, and `ndims` is the rank. """ return self._indices @property def values(self): """The non-zero values in the represented dense tensor. Returns: A 1-D Tensor of any data type. """ return self._values @property def op(self): """The `Operation` that produces `values` as an output.""" return self.values.op @property def dtype(self): """The `DType` of elements in this tensor.""" return self._values.dtype @property def dense_shape(self): """A 1-D Tensor of int64 representing the shape of the dense tensor.""" return self._dense_shape @property def graph(self): """The `Graph` that contains the index, value, and dense_shape tensors.""" return self._indices.graph def __str__(self): return "SparseTensor(indices=%s, values=%s, dense_shape=%s)" % ( self._indices, self._values, self._dense_shape) def eval(self, feed_dict=None, session=None): """Evaluates this sparse tensor in a `Session`. Calling this method will execute all preceding operations that produce the inputs needed for the operation that produces this tensor. *N.B.* Before invoking `SparseTensor.eval()`, its graph must have been launched in a session, and either a default session must be available, or `session` must be specified explicitly. Args: feed_dict: A dictionary that maps `Tensor` objects to feed values. See @{tf.Session.run} for a description of the valid feed values. session: (Optional.) The `Session` to be used to evaluate this sparse tensor. If none, the default session will be used. Returns: A `SparseTensorValue` object. """ indices, values, dense_shape = _eval_using_default_session( [self.indices, self.values, self.dense_shape], feed_dict, self.graph, session) return SparseTensorValue(indices, values, dense_shape) @staticmethod def _override_operator(operator, func): _override_helper(SparseTensor, operator, func) SparseTensorValue = collections.namedtuple( "SparseTensorValue", ["indices", "values", "dense_shape"]) def convert_to_tensor_or_sparse_tensor(value, dtype=None, name=None): """Converts value to a `SparseTensor` or `Tensor`. Args: value: A `SparseTensor`, `SparseTensorValue`, or an object whose type has a registered `Tensor` conversion function. dtype: Optional element type for the returned tensor. If missing, the type is inferred from the type of `value`. name: Optional name to use if a new `Tensor` is created. Returns: A `SparseTensor` or `Tensor` based on `value`. Raises: RuntimeError: If result type is incompatible with `dtype`. """ if dtype is not None: dtype = dtypes.as_dtype(dtype) if isinstance(value, SparseTensorValue): value = SparseTensor.from_value(value) if isinstance(value, SparseTensor): if dtype and not dtype.is_compatible_with(value.dtype): raise RuntimeError( "Sparse dtype: requested = %s, actual = %s" % ( dtype.name, value.dtype.name)) return value return ops.internal_convert_to_tensor( value, dtype=dtype, name=name)
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