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 #ifndef TENSORFLOW_LITE_TOCO_GRAPH_TRANSFORMATIONS_REMOVE_TRIVIAL_PASSTHROUGH_H_ 16 #define TENSORFLOW_LITE_TOCO_GRAPH_TRANSFORMATIONS_REMOVE_TRIVIAL_PASSTHROUGH_H_ 17 18 #include "tensorflow/lite/toco/graph_transformations/graph_transformations.h" 19 #include "tensorflow/lite/toco/model.h" 20 21 namespace toco { 22 23 // A "passthrough op" is an op that satisfies the following conditions: 24 // 1. One of its inputs is (per the semantics of that op) its "main input" 25 // for some notion of "main input" that is operator-specific; for example, 26 // for a Reshape op, the main input is the array being reshaped, not the 27 // other input which gives the new shape. 28 // 2. It has exactly one output. 29 // 3. It forwards exactly its main input to its single output. 30 // 31 // Examples include: 32 // 1. TensorFlow Identity ops. (Have one input). 33 // 2. TensorFlow Reshape ops when the input and output shapes agree. 34 // 3. Any binary operator, one of whose two inputs is a constant and is the 35 // neutral value for that operation. For example, a binary Add operator 36 // where one of its inputs is a constant array filled with zeros. 37 // 38 // A passthrough op is "trivial" and can be removed when it is possible to 39 // discard either its main input or output array, rerouting any 40 // edge involving it to the other of these two arrays. 41 // 42 // It is only possible to discard such an array if it is not explicitly 43 // designated as a global input/output array of the graph, e.g. the model's 44 // input arrays, output arrays, and any array involved in a RNN back-edge 45 // specified by the model. 46 // 47 // This function does not check that the given operator is a passthrough op: 48 // that's the responsibility of the caller. 49 // Given that it is a passthrough op, this function checks whether it is trivial 50 // and then discards it and returns true, or, if it's not trivial (if neither 51 // the input nor the output may be discarded), returns false. 52 bool RemoveTrivialPassthroughOp(GraphTransformation* transformation, 53 Model* model, std::size_t op_index, 54 int input_index = -1); 55 56 } // namespace toco 57 58 #endif // TENSORFLOW_LITE_TOCO_GRAPH_TRANSFORMATIONS_REMOVE_TRIVIAL_PASSTHROUGH_H_ 59