1/* Copyright 2016 The TensorFlow Authors. All Rights Reserved.
2
3Licensed under the Apache License, Version 2.0 (the "License");
4you may not use this file except in compliance with the License.
5You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9Unless required by applicable law or agreed to in writing, software
10distributed under the License is distributed on an "AS IS" BASIS,
11WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12See the License for the specific language governing permissions and
13limitations under the License.
14==============================================================================*/
15
16#ifndef TENSORFLOW_CORE_GRAPH_CONTROL_FLOW_H_
17#define TENSORFLOW_CORE_GRAPH_CONTROL_FLOW_H_
18
19#include <vector>
20
21#include "tensorflow/core/graph/graph.h"
22#include "tensorflow/core/lib/core/status.h"
23
24namespace tensorflow {
25
26// Control flow info for a graph node.
27struct ControlFlowInfo {
28 // 'frame' and 'parent_frame' are pointers to:
29 //
30 // a) One of the Enter nodes corresponding to the loop body, if the node
31 // executes inside a loop. If multiple tensors enter the while loop, it's
32 // undefined which Enter node will be used.
33 //
34 // b) SOURCE node (node.id() == Graph::kSourceId), if the node is not inside
35 // any of the while loops.
36
37 const Node* frame = nullptr; // frame of a node
38 const Node* parent_frame = nullptr; // parent frame of a node
39 string frame_name; // frame name of a node
40};
41
42// Clear and populate `info` with each node's frame and the level it belongs to.
43// We check the well-formedness of the graph:
44// 1) All inputs to a node must come from the same frame and have the same
45// "static" iteration level.
46// 2) Each frame has at most one LoopCond node.
47// 3) Each frame has a single parent frame.
48// If `unreachable_nodes` is set, return names of nodes unreachable from the
49// source node. We cannot build ControlFlowInfo for such nodes. They might be
50// pruned later.
51//
52// NOTE(yuanbyu): For now, we require all sends/recvs have iteration level 0.
53// This essentially means there can't be multiple serial Nexts in an iteration,
54// which all sane front-ends should satisfy.
55Status BuildControlFlowInfo(const Graph* g, std::vector<ControlFlowInfo>* info,
56 std::vector<string>* unreachable_nodes = nullptr);
57
58} // namespace tensorflow
59
60#endif // TENSORFLOW_CORE_GRAPH_CONTROL_FLOW_H_
61