1# Copyright 2017 The TensorFlow Authors. All Rights Reserved. 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); 4# you may not use this file except in compliance with the License. 5# You may obtain a copy of the License at 6# 7# http://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, 11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12# See the License for the specific language governing permissions and 13# limitations under the License. 14# ============================================================================== 15"""Special functions that only make sense for AutoGraph. 16 17These functions are meant to ensure feature parity between Python and AutoGraph, 18so that the exact same code works in both modes. In general, AutoGraph will 19replace these calls. 20""" 21 22from tensorflow.python.autograph.operators import data_structures 23from tensorflow.python.framework import constant_op 24from tensorflow.python.framework import tensor_util 25 26 27def _validate_list_constructor(elements, element_dtype, element_shape): 28 """Validates the inputs of tensor_list.""" 29 if element_dtype is not None and element_shape is not None: 30 return 31 if tensor_util.is_tf_type(elements): 32 return 33 if isinstance(elements, (list, tuple)): 34 if elements: 35 return 36 else: 37 raise ValueError( 38 'element_dtype and element_shape are required when elements are' 39 ' empty') 40 41 raise ValueError( 42 'unknown type for elements: {}; only Tensor, list and tuple are' 43 ' allowed'.format(type(elements))) 44 45 46def match_staging_level(value, like_value): 47 """Casts a value to be staged at the same level as another.""" 48 if tensor_util.is_tf_type(like_value): 49 return constant_op.constant(value) 50 return value 51 52 53def tensor_list(elements, 54 element_dtype=None, 55 element_shape=None, 56 use_tensor_array=False): 57 """Creates an tensor list and populates it with the given elements. 58 59 This function provides a more uniform access to tensor lists and tensor 60 arrays, and allows optional initialization. 61 62 Note: this function is a simplified wrapper. If you need greater control, 63 it is recommended to use the underlying implementation directly. 64 65 Args: 66 elements: Iterable[tf.Tensor, ...], the elements to initially fill the list 67 with 68 element_dtype: Optional[tf.DType], data type for the elements in the list; 69 required if the list is empty 70 element_shape: Optional[tf.TensorShape], shape for the elements in the list; 71 required if the list is empty 72 use_tensor_array: bool, whether to use the more compatible but restrictive 73 tf.TensorArray implementation 74 Returns: 75 Union[tf.Tensor, tf.TensorArray], the new list. 76 Raises: 77 ValueError: for invalid arguments 78 """ 79 _validate_list_constructor(elements, element_dtype, element_shape) 80 if use_tensor_array: 81 return data_structures.tf_tensor_array_new(elements, element_dtype, 82 element_shape) 83 else: 84 return data_structures.tf_tensor_list_new(elements, element_dtype, 85 element_shape) 86 87 88def stack(list_or_tensor, element_dtype=None, strict=True): 89 """Stacks the input, if it admits the notion of stacking. 90 91 For example, a list of tensors can be stacked into a larger tensor. This 92 function is similar to tf.stack, but it accepts non-lists and lists of 93 non-tensors as arguments. In the latter case, the function does nothing. 94 95 Args: 96 list_or_tensor: Any 97 element_dtype: tf.DType, optional dtypedtype for the elements in the list. 98 Required if the input is stackable, and the list is untyped. 99 strict: bool, if True an error is raised if the input is not stackable. 100 Otherwise the function is a no-op. 101 102 Returns: 103 Any, if the input is stackable, the result will be a tf.Tensor. Otherwise, 104 if strict=False, the result will be list_or_tensor. 105 106 Raises: 107 ValueError: if strict=True and the input is not stackable. 108 """ 109 if strict: 110 def raise_error(x): 111 raise ValueError('%s must be stackable when strict=True' % x) 112 original_call = raise_error 113 else: 114 original_call = lambda x: x 115 return data_structures.list_stack( 116 list_or_tensor, 117 data_structures.ListStackOpts( 118 element_dtype=element_dtype, original_call=original_call)) 119