/* Copyright 2017 The TensorFlow Authors. All Rights Reserved.

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,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef TENSORFLOW_CORE_GRAPPLER_OPTIMIZERS_GRAPH_OPTIMIZER_H_
#define TENSORFLOW_CORE_GRAPPLER_OPTIMIZERS_GRAPH_OPTIMIZER_H_

#include <string>

#include "tensorflow/core/framework/graph.pb.h"
#include "tensorflow/core/platform/env.h"
#include "tensorflow/core/platform/errors.h"
#include "tensorflow/core/platform/status.h"
#include "tensorflow/core/platform/types.h"

namespace tensorflow {
namespace grappler {

class Cluster;
struct GrapplerItem;

// An abstract interface for an algorithm for generating a candidate
// optimization of a GrapplerItem for running on a cluster.
class GraphOptimizer {
 public:
  GraphOptimizer() : deadline_usec_(0) {}
  virtual ~GraphOptimizer() {}

  virtual string name() const = 0;

  // Returns true if the optimizer requires a valid function library to perform
  // graph optimization. If false, optimized GrapplerItem will have a stub
  // instead of real function library (all function signatures and attributes
  // will be valid, but function body will be empty). Most of the optimizers
  // that do not instantiate functions should return true.
  virtual bool UsesFunctionLibrary() const = 0;

  // Routine called to allow an algorithm to propose a rewritten graph
  // for the graph, feeds and fetches in "item" to run more efficiently
  // on "cluster". If the returned status is Status::OK() then
  // *optimized_graph contains the rewritten graph.
  // Returns an error status if it failed to generate a solution.
  //
  // A return value of error::Aborted() can be used signal early termination of
  // the optimizer, e.g. if the optimization turned out to be a no-op. In this
  // case the content of *optimized_graph is undefined.
  virtual Status Optimize(Cluster* cluster, const GrapplerItem& item,
                          GraphDef* optimized_graph) = 0;

  // Subclasses may define a version of Optimize that consumes item.
  virtual Status Optimize(Cluster* cluster, GrapplerItem&& item,
                          GraphDef* optimized_graph) {
    return Optimize(cluster, item, optimized_graph);
  }

  // Method invoked by the framework so that it can provide feedback
  // on how well the "optimized_graph" (produced as *optimized_graph from a
  // call to Optimize) performed.  Lower "result" scores are better.
  virtual void Feedback(Cluster* cluster, const GrapplerItem& item,
                        const GraphDef& optimized_graph, double result) = 0;

  // Set deadline in microseconds since epoch. A value of zero means no
  // deadline.
  void set_deadline_usec(uint64 deadline_usec) {
    deadline_usec_ = deadline_usec;
  }
  uint64 deadline_usec() const { return deadline_usec_; }
  bool DeadlineExceeded() const {
    return deadline_usec_ > 0 && Env::Default()->NowMicros() > deadline_usec_;
  }

 private:
  uint64 deadline_usec_;
};

#define GRAPPLER_RETURN_IF_DEADLINE_EXCEEDED()                              \
  do {                                                                      \
    if (this->DeadlineExceeded()) {                                         \
      return errors::DeadlineExceeded(this->name(), " exceeded deadline."); \
    }                                                                       \
  } while (0)

}  // end namespace grappler
}  // end namespace tensorflow

#endif  // TENSORFLOW_CORE_GRAPPLER_OPTIMIZERS_GRAPH_OPTIMIZER_H_
