EVOLUTION-MANAGER

Edit File: subgraph.h

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,
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limitations under the License.
==============================================================================*/

#ifndef TENSORFLOW_CORE_GRAPH_SUBGRAPH_H_
#define TENSORFLOW_CORE_GRAPH_SUBGRAPH_H_

#include <string>

#include "tensorflow/core/framework/device_attributes.pb.h"
#include "tensorflow/core/graph/graph.h"
#include "tensorflow/core/graph/node_builder.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/lib/gtl/array_slice.h"
#include "tensorflow/core/protobuf/config.pb.h"

namespace tensorflow {
namespace subgraph {

// Information about a graph rewritten by `RewriteGraphForExecution()`.
struct RewriteGraphMetadata {
  // The element type of each tensor fed to this subgraph. The order
  // of types corresponds to the order of tensor names in
  // `fed_outputs` when calling `RewriteGraphForExecution()`.
  DataTypeVector feed_types;
  // The element type of each tensor fetched from this subgraph. The
  // order of types corresponds to the order of tensor names in
  // `fetch_outputs` when calling `RewriteGraphForExecution()`.
  DataTypeVector fetch_types;
};

// Describes the action to take on a particular tensor endpoint (described by
// a "<node_name>:<output_index>" pair) when pruning the graph.
//
// The `AddNode()` method must be overridden to describe this action. The method
// will be invoked once during `RewriteGraphForExecution()` with tensor endpoint
// named by `endpoint_name`, and it may either create a single new node, or fail
// with an error if the resulting graph would be invalid.
class PruneRewrite {
 public:
  // `endpoint_name` and `device_info` must outlive this object.
  PruneRewrite(const string* endpoint_name, const DeviceAttributes* device_info)
      : endpoint_name_(endpoint_name), device_info_(device_info) {}
  virtual ~PruneRewrite() {}

// Creates a new node whose output replaces the given `tensor` in graph `g`.
  // The node will be assigned to the device named in `device_info`.
  virtual Status AddNode(Graph* g, NodeBuilder::NodeOut tensor,
                         Node** out_node) = 0;

// Returns the name of the tensor to which this rewrite applies.
  const string& endpoint_name() { return *endpoint_name_; }

protected:
  // The device on which the new node will be created.
  const DeviceAttributes& device_info() { return *device_info_; }

private:
  const string* const endpoint_name_;          // Not owned.
  const DeviceAttributes* const device_info_;  // Not owned.
};

// Rewrite the graph structure of "*g" to deal with feeding node
// outputs, fetching node outputs, and only running a subset of the
// graph.  "fed_outputs" and "fetch_outputs" are both lists of
// output tensor identifiers in the form of
// "<name>[:<optional_output_index>]", and "target_nodes_str" is a
// lists of target node names in "*g" "g".
//
// In the resulting graph "*g", output edges in "fed_outputs" have
// been redirected to special "_recv" nodes introduced into the graph.
// If these fed nodes are not needed in order to compute the effects
// of the nodes in "target_node_names" and "fetch_outputs", then these may
// be omitted from the graph.
//
// In the resulting graph "*g", additional "_send" nodes are connected
// to every output in "fetch_outputs".  These "_send" nodes are set up
// to execute on the device described by device_info.
//
// On success, returns OK, and sets "*g" to a version of "*g"
// that represents the portions of the graph necessary for producing
// the output of all nodes listed in "target_node_names" and fetching the
// specific node outputs specified in "fetch_outputs".
//
// On failure, returns the error status. Possible errors include:
//    - fed output "node:output_index" does not exist in "*g"
//    - fetch output "node:output_index" does not exist in "*g"
//    - target node "node" does not exist in "*g"
Status RewriteGraphForExecution(
    Graph* g, const gtl::ArraySlice<string>& fed_outputs,
    const gtl::ArraySlice<string>& fetch_outputs,
    const gtl::ArraySlice<string>& target_node_names,
    const DeviceAttributes& device_info, bool use_function_convention,
    RewriteGraphMetadata* out_metadata);

// A more general version of the above function that supports
// customizable rewriting actions for each fed and fetched tensor.
Status RewriteGraphForExecution(
    Graph* g, const std::vector<std::unique_ptr<PruneRewrite>>& feed_rewrites,
    const std::vector<std::unique_ptr<PruneRewrite>>& fetch_rewrites,
    const gtl::ArraySlice<string>& target_node_names,
    RewriteGraphMetadata* out_metadata);

/////////////////////////////////////////////////////////
// Custom rewrite actions for fed and fetched tensors. //
/////////////////////////////////////////////////////////

// A rewrite action that adds an _Arg node for a fed tensor.
class ArgFeedRewrite : public PruneRewrite {
 public:
  ArgFeedRewrite(const string* endpoint_name,
                 const DeviceAttributes* device_info, int32 arg_index)
      : PruneRewrite(endpoint_name, device_info), arg_index_(arg_index) {}
  Status AddNode(Graph* g, NodeBuilder::NodeOut feed_tensor,
                 Node** out_node) override;

private:
  const int32 arg_index_;
};

// A rewrite action that adds a client-terminated _Recv node for a fed tensor.
class RecvFeedRewrite : public PruneRewrite {
 public:
  using PruneRewrite::PruneRewrite;
  Status AddNode(Graph* g, NodeBuilder::NodeOut feed_tensor,
                 Node** out_node) override;
};

// A rewrite action that adds a _Retval node for a fetched tensor.
class RetvalFetchRewrite : public PruneRewrite {
 public:
  RetvalFetchRewrite(const string* endpoint_name,
                     const DeviceAttributes* device_info, int32 retval_index)
      : PruneRewrite(endpoint_name, device_info), retval_index_(retval_index) {}
  Status AddNode(Graph* g, NodeBuilder::NodeOut fetch_tensor,
                 Node** out_node) override;

private:
  const int32 retval_index_;
};

// A rewrite action that adds a client-terminated _Send node for a
// fetched tensor.
class SendFetchRewrite : public PruneRewrite {
 public:
  using PruneRewrite::PruneRewrite;
  Status AddNode(Graph* g, NodeBuilder::NodeOut fetch_tensor,
                 Node** out_node) override;
};

}  // namespace subgraph
}  // namespace tensorflow

#endif  // TENSORFLOW_CORE_GRAPH_SUBGRAPH_H_