NTSession.h

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/* Copyright 2015 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.
==============================================================================*/

/*
This file is an adaptation of the original direct_session.h file located at
https://github.com/tensorflow/tensorflow/blob/v1.3.0/tensorflow/core/common_runtime/direct_session.h
to meet the demands of the software environment developed and used by the CMS collaboration.

Changes:
  - Renamed the session class to NTSession (NT = non-threading)
  - Renamed some members to refelct that change
  - Removed the thread_pools_ member
  - Set the session handle to "no_threads"
  - Removed the ThreadPool arguments from GetOrCreateExecutors and SchedClosure
  - Removed obsolete helper functions NumInterOpThreadsFromSessionOptions,
    NewThreadPoolFromSessionOptions, NewThreadPoolFromThreadPoolOptions and GlobalThreadPool
  - Renamed the session factory class to NTSessionFactory
  - Renamed the session registrar class to NTSessionRegistrar
  - Renamed include guard to reflect location within CMSSW
*/

#ifndef PHYSICSTOOLS_TENSORFLOW_NTSESSION_H
#define PHYSICSTOOLS_TENSORFLOW_NTSESSION_H

#include <atomic>
#include <memory>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#include "tensorflow/core/common_runtime/costmodel_manager.h"
#include "tensorflow/core/common_runtime/debugger_state_interface.h"
#include "tensorflow/core/common_runtime/device_mgr.h"
#include "tensorflow/core/common_runtime/device_set.h"
#include "tensorflow/core/common_runtime/executor.h"
#include "tensorflow/core/common_runtime/rendezvous_mgr.h"
#include "tensorflow/core/common_runtime/session_factory.h"
#include "tensorflow/core/common_runtime/simple_graph_execution_state.h"
#include "tensorflow/core/framework/cancellation.h"
#include "tensorflow/core/framework/graph.pb.h"
#include "tensorflow/core/framework/session_state.h"
#include "tensorflow/core/framework/tensor.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/platform/macros.h"
#include "tensorflow/core/platform/mutex.h"
#include "tensorflow/core/platform/types.h"
#include "tensorflow/core/public/session.h"

namespace tensorflow {

class CostModel;
class DebugGateway;
class Device;
class NTSessionFactory;

class NTSession : public Session {
 public:
  typedef std::function<void(Session*)> CloseCallback;

  // Takes ownership of 'device_mgr'.
  // 'factory' is used to unregister the NTSession with 'factory' when its
  // closed. This ensures that Reset requests from the 'factory' don't get sent
  // to sessions that are already closed.
  NTSession(const SessionOptions& options, const DeviceMgr* device_mgr,
                NTSessionFactory* factory);
  ~NTSession() override;

  typedef std::vector<std::pair<string, Tensor>> NamedTensorList;
  typedef std::unordered_map<StringPiece, Node*, StringPiece::Hasher>
      NameNodeMap;

  ::tensorflow::Status Create(const GraphDef& graph) override;
  ::tensorflow::Status Extend(const GraphDef& graph) override;
  ::tensorflow::Status Run(const NamedTensorList& inputs,
                           const std::vector<string>& output_names,
                           const std::vector<string>& target_nodes,
                           std::vector<Tensor>* outputs) override;

  // NOTE: Experimental and subject to change.
  ::tensorflow::Status Run(const ::tensorflow::RunOptions& run_options,
                           const NamedTensorList& inputs,
                           const std::vector<string>& output_names,
                           const std::vector<string>& target_nodes,
                           std::vector<Tensor>* outputs,
                           RunMetadata* run_metadata) override;

  // NOTE: PRunSetup and PRun are added to support partial execution. This
  // feature is experimental and subject to change.
  ::tensorflow::Status PRunSetup(const std::vector<string>& input_names,
                                 const std::vector<string>& output_names,
                                 const std::vector<string>& target_nodes,
                                 string* handle) override;
  ::tensorflow::Status PRun(const string& handle, const NamedTensorList& inputs,
                            const std::vector<string>& output_names,
                            std::vector<Tensor>* outputs) override;

  // Reset clears 'containers' from the device_mgr of the NTSession.
  // If 'containers' is empty, then Reset clears the default container.
  ::tensorflow::Status Reset(const std::vector<string>& containers);

  ::tensorflow::Status ListDevices(
      std::vector<DeviceAttributes>* response) override;
  ::tensorflow::Status Close() override;

  void ExportCostModels(CostModelManager::CostModelMap* cost_models) {
    cost_model_manager_.ExportCostModels(cost_models);
  }

 private:
  typedef NTSession ME;

  // We create one executor and its dependent library runtime for
  // every partition.
  struct PerPartitionExecutorsAndLib {
    Graph* graph = nullptr;
    std::unique_ptr<FunctionLibraryRuntime> flib;
    std::unique_ptr<Executor> executor;
  };

  // An ExecutorsAndKeys is created for a given set of feeds/fetches.
  // 'step_count' is the number of times this graph is executed.
  // 'graph' is the entire graph being executed. 'name_to_node'
  // maps node name to node. We keep 'graph' and 'name_to_node' only in
  // the case of partial runs. Each item in 'items' is the executor for
  // a partition of the graph bundled with its dependent library runtime.
  // 'input_keys' are the rendezvous keys for the feeds and 'output_keys'
  // are rendezvous keys for the fetches.
  // 'flib_def' is the function library used by graphs in 'items'.
  // TODO(phawkins): currently partitions always share the same function
  // library. Consider giving each partition its own function library to enable
  // per-partition rewrites.
  struct ExecutorsAndKeys {
    ExecutorsAndKeys() : step_count(0) {}

    std::atomic_int_fast64_t step_count;
    std::unique_ptr<Graph> graph;
    NameNodeMap name_to_node;
    std::unique_ptr<FunctionLibraryDefinition> flib_def;
    std::vector<PerPartitionExecutorsAndLib> items;
    std::unordered_map<string, size_t> input_name_to_index;
    std::unordered_map<string, string> input_name_to_rendezvous_key;
    std::unordered_map<string, size_t> output_name_to_index;
    std::unordered_map<string, string> output_name_to_rendezvous_key;

    DataTypeVector input_types;
    DataTypeVector output_types;
  };

  // For each live partial execution, the session maintains a RunState.
  // 'status' is the current status of this partial execution. 'executor_done'
  // is "notified" when all executors are done. 'pending_inputs' are the set
  // of pending feeds and 'pending_outputs' are the set of pending fetches.
  struct RunState {
    mutex mu_;
    Status status GUARDED_BY(mu_);
    IntraProcessRendezvous* rendez = nullptr;
    std::unique_ptr<StepStatsCollector> collector;
    Notification executors_done;
    std::unordered_map<string, bool> pending_inputs;   // true if fed
    std::unordered_map<string, bool> pending_outputs;  // true if fetched
    TensorStore tensor_store;
    ScopedStepContainer step_container;

    RunState(int64 step_id, const std::vector<Device*>* devices);

    RunState(const std::vector<string>& pending_input_names,
             const std::vector<string>& pending_output_names, int64 step_id,
             const std::vector<Device*>* devices);

    // Returns true if all pending inputs and outputs have been completed.
    bool PendingDone() const;

    ~RunState();
  };

  struct RunStateArgs {
    RunStateArgs(const DebugOptions& options) : debug_options(options) {}

    bool is_partial_run = false;
    string handle;
    std::unique_ptr<Graph> graph;
    const DebugOptions& debug_options;
  };

  // Initializes the base execution state given the 'graph',
  // if not already initialized.
  Status MaybeInitializeExecutionState(const GraphDef& graph,
                                       bool* out_already_initialized)
      EXCLUSIVE_LOCKS_REQUIRED(graph_def_lock_);

  // Retrieves an already existing set of executors to run 'inputs' and
  // 'outputs', or creates and caches them for future use.
  ::tensorflow::Status GetOrCreateExecutors(
      gtl::ArraySlice<string> inputs,
      gtl::ArraySlice<string> outputs, gtl::ArraySlice<string> target_nodes,
      ExecutorsAndKeys** executors_and_keys, RunStateArgs* run_state_args);

  // Creates several graphs given the existing graph_def_ and the
  // input feeds and fetches, given 'devices'. The graphs share a common
  // function library 'flib_def'.
  ::tensorflow::Status CreateGraphs(
      const BuildGraphOptions& options,
      std::unordered_map<string, std::unique_ptr<Graph>>* outputs,
      std::unique_ptr<FunctionLibraryDefinition>* flib_def,
      RunStateArgs* run_state_args, DataTypeVector* input_types,
      DataTypeVector* output_types);

  ::tensorflow::Status ExtendLocked(const GraphDef& graph)
      EXCLUSIVE_LOCKS_REQUIRED(graph_def_lock_);

  ::tensorflow::Status ResourceHandleToInputTensor(
      const Tensor& resource_tensor, Tensor* retrieved_tensor);

  // Feeds more inputs to the executors, triggering further execution.
  ::tensorflow::Status SendPRunInputs(
      const std::vector<std::pair<string, Tensor>>& inputs,
      const ExecutorsAndKeys* executors_and_keys,
      IntraProcessRendezvous* rendez);

  // Fetches more outputs from the executors. It waits until the output
  // tensors are computed.
  ::tensorflow::Status RecvPRunOutputs(
      const std::vector<string>& output_names,
      const ExecutorsAndKeys* executors_and_keys, RunState* run_state,
      std::vector<Tensor>* outputs);

  // Check if the specified fetches can be computed from the feeds
  // that we have already provided.
  ::tensorflow::Status CheckFetch(
      const std::vector<std::pair<string, Tensor>>& feeds,
      const std::vector<string>& fetches,
      const ExecutorsAndKeys* executors_and_keys, const RunState* run_state);

  // Use the appropriate WaitForNotification function based on whether
  // operation_timeout_in_ms is greater than 0.
  //
  // If the timeout expires, the `cm->StartCancel()` will be called.
  ::tensorflow::Status WaitForNotification(Notification* n,
                                           int64 timeout_in_ms);
  void WaitForNotification(RunState* run_state, CancellationManager* cm,
                           int64 timeout_in_ms);

  ::tensorflow::Status CheckNotClosed() {
    mutex_lock l(closed_lock_);
    if (closed_) return errors::Cancelled("Session has been closed.");
    return ::tensorflow::Status::OK();
  }

  ::tensorflow::Status CreateDebuggerState(
      const DebugOptions& debug_options, int64 session_run_index,
      int64 executor_step_index, const std::vector<string>& input_names,
      const std::vector<string>& output_names,
      const std::vector<string>& target_names,
      std::unique_ptr<DebuggerStateInterface>* debugger_state);

  ::tensorflow::Status DecorateAndPublishGraphForDebug(
      const DebugOptions& debug_options, Graph* graph, Device* device);

  const SessionOptions options_;

  // Device structures.
  const std::unique_ptr<const DeviceMgr> device_mgr_;
  std::vector<Device*> devices_;  // not owned
  DeviceSet device_set_;

  string session_handle_;
  bool graph_created_ GUARDED_BY(graph_def_lock_) = false;

  mutex graph_def_lock_;
  GraphDef graph_def_ GUARDED_BY(graph_def_lock_);

  Status init_error_;  // Set to an error if construction failed.

  // If true, blocks until device has finished all queued operations in a step.
  bool sync_on_finish_ = true;
  void SchedClosure(std::function<void()> c);

  mutex executor_lock_;  // protects executors_
  // Holds mappings from signature to the executors that process
  // it. The reason for a level of indirection around mapped_type is
  // to guarantee address stability.
  // The map value is a shared_ptr since multiple map keys can point to the
  // same ExecutorsAndKey object.
  std::unordered_map<string, std::shared_ptr<ExecutorsAndKeys>> executors_
      GUARDED_BY(executor_lock_);

  // Holds mappings from handle to partial run state.
  std::unordered_map<string, std::unique_ptr<RunState>> partial_runs_
      GUARDED_BY(executor_lock_);

  // This holds all the tensors that are currently alive in the session.
  SessionState session_state_;

  NTSessionFactory* const factory_;  // not owned
  CancellationManager* cancellation_manager_;

  // Map of placed stateful nodes, i.e. nodes for which is_stateful()
  // is true, such as "params" and "queue" nodes.  Once placed these
  // nodes can not be moved to a different device.  Maps node names to
  // device names.
  std::unordered_map<string, string> stateful_placements_
      GUARDED_BY(graph_def_lock_);

  // Execution_state; used when placing the entire graph.
  std::unique_ptr<SimpleGraphExecutionState> execution_state_
      GUARDED_BY(graph_def_lock_);

  // The function library, before any rewrites or optimizations have been
  // performed. In particular, CreateGraphs() may need to modify the function
  // library; it copies and modifies the function library.
  std::unique_ptr<FunctionLibraryDefinition> flib_def_;

  // true if the Session has been Closed.
  mutex closed_lock_;
  bool closed_ GUARDED_BY(closed_lock_) = false;

  // For generating unique names for this session instance.
  std::atomic<int64> edge_name_counter_ = {0};
  std::atomic<int64> handle_name_counter_ = {0};

  // For generating step ids that are unique across all sessions.
  static std::atomic_int_fast64_t step_id_counter_;

  // Global timeout for all blocking operations in this session.
  const int64 operation_timeout_in_ms_ = 0;

  // Manages all the cost models for the graphs executed in this session.
  CostModelManager cost_model_manager_;

  Executor::Args::NodeOutputsCallback node_outputs_callback_ = nullptr;

  TF_DISALLOW_COPY_AND_ASSIGN(NTSession);

  // EXPERIMENTAL: debugger (tfdbg) related
  friend class DebugGateway;
};

}  // end namespace tensorflow

#endif  // PHYSICSTOOLS_TENSORFLOW_NTSESSION_H