/* Copyright 2018 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_LITE_CORE_SUBGRAPH_H_
#define TENSORFLOW_LITE_CORE_SUBGRAPH_H_

#include <stdarg.h>
#include <stddef.h>

#include <atomic>
#include <cstdint>
#include <map>
#include <memory>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#include "tensorflow/compiler/mlir/lite/allocation.h"
#include "tensorflow/lite/allocation.h"
#include "tensorflow/lite/array.h"
#include "tensorflow/lite/c/common_internal.h"
#include "tensorflow/lite/core/api/error_reporter.h"
#include "tensorflow/lite/core/api/op_resolver.h"
#include "tensorflow/lite/core/api/profiler.h"
#include "tensorflow/lite/core/c/common.h"
#include "tensorflow/lite/core/macros.h"
#include "tensorflow/lite/experimental/resource/initialization_status.h"
#include "tensorflow/lite/experimental/resource/resource_base.h"
#include "tensorflow/lite/graph_info.h"
#include "tensorflow/lite/interpreter_options.h"
#include "tensorflow/lite/memory_planner.h"
#include "tensorflow/lite/util.h"

namespace tflite {

#ifndef DOXYGEN_SKIP
class SingleOpModel;  // Class for friend declarations.

namespace internal {
class CommonOpaqueConversionUtil;  // Class for friend declarations.
}

namespace async {
class AsyncSubgraph;  // Class for friend declarations.
}

namespace impl {
class Interpreter;         // Class for friend declarations.
class InterpreterBuilder;  // Class for friend declarations.
class SignatureRunner;     // Class for friend declarations.
}  // namespace impl

namespace delegates {
namespace test_utils {
class TestDelegate;  // Class for friend declarations.
}  // namespace test_utils
}  // namespace delegates
#endif  // DOXYGEN_SKIP

class Subgraph {
 public:
#ifndef DOXYGEN_SKIP
  friend class ::tflite::impl::Interpreter;
  friend class ::tflite::impl::SignatureRunner;
  friend class SingleOpModel;
  friend class internal::CommonOpaqueConversionUtil;
#endif  // DOXYGEN_SKIP
  Subgraph(ErrorReporter* error_reporter,
           TfLiteExternalContext** external_contexts,
           std::vector<std::unique_ptr<Subgraph>>* subgraphs,
           resource::ResourceMap* resources,
           resource::ResourceIDMap* resource_ids,
           resource::InitializationStatusMap* initialization_status_map,
           int subgraph_index = kInvalidSubgraphIndex);

  Subgraph(const Subgraph&) = delete;

  // Subgraphs should be movable but not copyable.
  Subgraph(Subgraph&&) = default;
  Subgraph& operator=(const Subgraph&) = delete;
  virtual ~Subgraph();

  // Provide a list of tensor indexes that are inputs to the model.
  // Each index is bound check and this modifies the consistent_ flag of the
  // interpreter.
  TfLiteStatus SetInputs(std::vector<int> inputs);

  // Provide a list of tensor indexes that are outputs to the model
  // Each index is bound check and this modifies the consistent_ flag of the
  // interpreter.
  TfLiteStatus SetOutputs(std::vector<int> outputs);

  // Provide a list of tensor indexes that are variable tensors.
  // Each index is bound check and this modifies the consistent_ flag of the
  // interpreter.
  TfLiteStatus SetVariables(std::vector<int> variables);

  // Adds a node with the given parameters and returns the index of the new
  // node in `node_index` (optionally). Interpreter will take ownership of
  // `builtin_data` and destroy it with `free`. Ownership of 'init_data'
  // remains with the caller.
  TfLiteStatus AddNodeWithParameters(const std::vector<int>& inputs,
                                     const std::vector<int>& outputs,
                                     const std::vector<int>& intermediates,
                                     const char* init_data,
                                     size_t init_data_size, void* builtin_data,
                                     const TfLiteRegistration* registration,
                                     int* node_index = nullptr);

  // Adds `tensors_to_add` tensors, preserving pre-existing Tensor entries.
  // The value pointed to by `first_new_tensor_index` will be set to the
  // index of the first new tensor if `first_new_tensor_index` is non-null.
  TfLiteStatus AddTensors(int tensors_to_add,
                          int* first_new_tensor_index = nullptr);

  // Set description of inputs/outputs/data/fptrs for node `node_index`.
  // This variant assumes an external buffer has been allocated of size
  // bytes. The lifetime of buffer must be ensured to be greater or equal
  // to Interpreter. `quantization` ownership is passed to the subgraph.
  // `buffer_identifier`: An optional value to identify the buffer. If set to
  // a value other than kTfLiteNoBufferIdentifier, this tensor is considered a
  // constant tensor shared across multiple subgraphs / interpreters.
  // `external_buffer_id`: An optional value to identify the external buffer. If
  // set to a value other than kTfLiteNoBufferIdentifier, this tensor is
  // considered a tensor using an external buffer shared across multiple
  // subgraphs / interpreters.
  inline TfLiteStatus SetTensorParametersReadOnly(
      int tensor_index, TfLiteType type, const char* name,
      const std::vector<int>& dims, TfLiteQuantization quantization,
      const char* buffer, size_t bytes, const Allocation* allocation = nullptr,
      TfLiteSparsity* sparsity = nullptr,
      size_t buffer_identifier = kTfLiteNoBufferIdentifier,
      size_t external_buffer_id = kTfLiteNoBufferIdentifier) {
    return SetTensorParametersReadOnly(tensor_index, type, name, dims.size(),
                                       dims.data(), quantization, buffer, bytes,
                                       allocation, sparsity, buffer_identifier,
                                       external_buffer_id);
  }
  TfLiteStatus SetTensorParametersReadOnly(
      int tensor_index, TfLiteType type, const char* name, size_t ndims,
      const int* dims, TfLiteQuantization quantization, const char* buffer,
      size_t bytes, const Allocation* allocation = nullptr,
      TfLiteSparsity* sparsity = nullptr,
      size_t buffer_identifier = kTfLiteNoBufferIdentifier,
      size_t external_buffer_id = kTfLiteNoBufferIdentifier);

  // Set description of inputs/outputs/data/fptrs for node `node_index`.
  // This variant assumes an external buffer has been allocated of size
  // bytes. The lifetime of buffer must be ensured to be greater or equal
  // to Interpreter. `quantization` ownership is passed to the subgraph.
  inline TfLiteStatus SetTensorParametersReadWrite(
      int tensor_index, TfLiteType type, const char* name,
      const std::vector<int>& dims, TfLiteQuantization quantization,
      bool is_variable = false, const std::vector<int>& dims_signature = {},
      size_t external_buffer_id = 0) {
    if (dims_signature.empty()) {
      return SetTensorParametersReadWrite(
          tensor_index, type, name, dims.size(), dims.data(), quantization,
          is_variable, 0, nullptr, external_buffer_id);
    }
    return SetTensorParametersReadWrite(
        tensor_index, type, name, dims.size(), dims.data(), quantization,
        is_variable, dims_signature.size(), dims_signature.data(),
        external_buffer_id);
  }
  TfLiteStatus SetTensorParametersReadWrite(
      int tensor_index, TfLiteType type, const char* name, size_t ndims,
      const int* dims, TfLiteQuantization quantization,
      bool is_variable = false, size_t ndims_signature = 0,
      const int* dims_signature = nullptr, size_t external_buffer_id = 0);

  // Set the external buffer ID for a tensor. This is used for tensors whose
  // data is stored in an external file.
  void SetTensorExternalBufferId(size_t tensor_index,
                                 size_t external_buffer_id) {
    if (external_buffer_id != kTfLiteNoBufferIdentifier &&
        external_buffer_id != 0) {
      tensor_external_buffer_ids_[tensor_index] = external_buffer_id;
    }
  }

  // Get all tensors in the subgraph.
  //
  // Warning: No guarantee is given about address stability. Operations
  // (including but not limited to: `Invoke`, `AddTensors`) may invalidate the
  // pointer returned by this function.
  TfLiteTensor* tensors() { return context_.tensors; }

  // Get a mutable tensor data structure.
  //
  // Warning: No guarantee is given about address stability. Operations
  // (including but not limited to: `Invoke`, `AddTensors`) may invalidate the
  // pointer returned by this function.
  TfLiteTensor* tensor(int tensor_index) {
    if (tensor_index < 0 ||
        static_cast<size_t>(tensor_index) >= context_.tensors_size) {
      return nullptr;
    }
    return &context_.tensors[tensor_index];
  }

  // Get an immutable tensor data structure.
  //
  // Warning: No guarantee is given about address stability. Operations
  // (including but not limited to: `Invoke`, `AddTensors`) may invalidate the
  // pointer returned by this function.
  const TfLiteTensor* tensor(int tensor_index) const {
    if (tensor_index < 0 ||
        static_cast<size_t>(tensor_index) >= context_.tensors_size) {
      return nullptr;
    }
    return &context_.tensors[tensor_index];
  }

  // Read only access to list of inputs.
  std::vector<int>& inputs() { return inputs_; }

  // Read only access to list of inputs.
  const std::vector<int>& inputs() const { return inputs_; }

  // Read only access to list of outputs.
  std::vector<int>& outputs() { return outputs_; }

  // Read only access to list of outputs.
  const std::vector<int>& outputs() const { return outputs_; }

  // Read only access to list of variable tensors.
  std::vector<int>& variables() { return variables_; }

  // Read only access to list of variable tensors.
  const std::vector<int>& variables() const { return variables_; }

  // WARNING: Experimental interface, subject to change.
  // TODO(ycling): Move this function to an external context interface.
  resource::ResourceMap& resources() { return *resources_; }

  resource::ResourceMap* resources_ptr() { return resources_; }

  // WARNING: Experimental interface, subject to change.
  // TODO(b/149099381): Move this function to an external context interface.
  resource::ResourceIDMap& resource_ids() { return *resource_ids_; }

  // WARNING: Experimental interface, subject to change.
  // TODO(b/149099381): Move this function to an external context interface.
  resource::InitializationStatusMap& initialization_status_map() {
    return *initialization_status_map_;
  }

  size_t tensors_size() const { return tensors_.size(); }

  // Return the number of ops in the model.
  size_t nodes_size() const { return nodes_and_registration_.size(); }

  // Return vector of node indices in the order of execution.
  std::vector<int>& execution_plan() { return execution_plan_; }

  // Return read-only vector of node indices in the order of execution.
  const std::vector<int>& execution_plan() const { return execution_plan_; }

  // Return read-only vector of node indices in the order of execution before
  // any delegate was applied.
  //
  // Note: if no delegate is applied, this vector will be empty.
  const std::vector<int>& pre_delegation_execution_plan() const {
    return pre_delegation_execution_plan_;
  }

  const std::vector<std::pair<TfLiteNode, TfLiteRegistration>>&
  nodes_and_registration() const {
    return nodes_and_registration_;
  }

  // Get a pointer to an operation and registration data structure if in bounds.
  const std::pair<TfLiteNode, TfLiteRegistration>* node_and_registration(
      int node_index) const {
    if (node_index < 0 || static_cast<size_t>(node_index) >= nodes_size())
      return nullptr;
    return &nodes_and_registration_[node_index];
  }

  // Change the dimensionality of a given tensor.
  //
  // Note, this is only acceptable for tensor indices that are inputs.
  TfLiteStatus ResizeInputTensor(int tensor_index, const int* dims_data,
                                 int rank);

  // Change the dimensionality of a given tensor.
  //
  // Note, this is only acceptable for tensor indices that are inputs.
  TfLiteStatus ResizeInputTensor(int tensor_index,
                                 const std::vector<int>& dims);

  // WARNING: Experimental interface, subject to change
  // Change the dimensionality of a given tensor. This is only acceptable for
  // tensor indices that are inputs or variables. Only unknown dimensions can be
  // resized with this function. Unknown dimensions are indicated as `-1` in the
  // `dims_signature` attribute of a `TfLiteTensor`. Returns status of failure
  // or success.
  TfLiteStatus ResizeInputTensorStrict(int tensor_index,
                                       const std::vector<int>& dims);

  // This releases memory held by non-persistent tensors. It does NOT re-perform
  // memory planning.
  // AllocateTensors needs to be called before next invocation.
  TfLiteStatus ReleaseNonPersistentMemory();

  // WARNING: Experimental interface, subject to change
  // This API releases memory held by the given subgraph. This method is
  // designed to release memory of control flow subgraphs.
  // AllocateTensors needs to be called before next invocation.
  TfLiteStatus ReleaseMemory();

  // Update allocations for all tensors. This will redim dependent tensors using
  // the input tensor dimensionality as given. This is relatively expensive.
  // If you know that your sizes are not changing, you need not call this.
  // Returns status of success or failure.
  TfLiteStatus AllocateTensors();

  // Returns the number of times each tensor is consumed. Subgraph output
  // tensors are considered as consumed.
  std::vector<int> GetInputTensorsCount();

  // Invoke the subgraph (run the whole graph in dependency order).
  //
  // NOTE: It is possible that the interpreter is not in a ready state
  // to evaluate (i.e. if a ResizeTensor() has been performed without an
  // AllocateTensors().
  // Returns status of success or failure.
  TfLiteStatus Invoke();

  // Entry point for C node plugin API to report an error.
  void ReportError(const char* format, ...);

  // Return the subgraph specific context.
  TfLiteContext* context() { return &context_; }
  const TfLiteContext* context() const { return &context_; }

  // Set the value of an external context.
  void SetExternalContext(TfLiteExternalContextType type,
                          TfLiteExternalContext* ctx);
  // Get the half precision flag.
  // WARNING: This is an experimental API and subject to change.
  bool GetAllowFp16PrecisionForFp32() const {
    return context_.allow_fp32_relax_to_fp16;
  }

  // Sets the cancellation function pointer in order to cancel a request in the
  // middle of a call to Invoke(). The interpreter queries this function during
  // inference, between op invocations; when it returns true, the interpreter
  // will abort execution and return `kTfLiteError`. The `data` parameter
  // contains any data used by the cancellation function, and if non-null,
  // remains owned by the caller.
  // WARNING: This is an experimental API and subject to change.
  void SetCancellationFunction(void* data, bool (*check_cancelled_func)(void*));

  // Ensure the data in `tensor.data` is readable. In case delegate is used,
  // it might require to copy the data from delegate buffer to raw memory.
  // WARNING: This is an experimental API and subject to change.
  TfLiteStatus EnsureTensorDataIsReadable(int tensor_index);

  // The default capacity of `tensors_` vector.
  static constexpr int kTensorsReservedCapacity = 128;
  // The capacity headroom of `tensors_` vector before calling ops'
  // `prepare` and `invoke` function. In these functions, it's guaranteed
  // allocating up to `kTensorsCapacityHeadroom` more tensors won't invalidate
  // pointers to existing tensors.
  static constexpr int kTensorsCapacityHeadroom = 16;

  // Reset all variable tensors to the default value.
  // If a variable tensor doesn't have a buffer, reset it to zero.
  // TODO(b/115961645): Implement - If a variable tensor has a buffer, reset it
  // to the value of the buffer.
  // WARNING: This is an experimental API and subject to change.
  TfLiteStatus ResetVariableTensors();

  void SetProfiler(Profiler* profiler, int associated_subgraph_idx) {
    if (!profiler) {
      profiler_.reset(nullptr);
      context_.profiler = nullptr;
    } else {
      profiler_ = std::make_unique<SubgraphAwareProfiler>(
          profiler, associated_subgraph_idx);
      context_.profiler = profiler_.get();
    }
  }

  Profiler* GetProfiler() { return profiler_.get(); }

  // Returns a pointer to vector of subgraphs.
  // WARNING: This is an experimental API and subject to change.
  std::vector<std::unique_ptr<Subgraph>>* GetSubgraphs() const {
    return subgraphs_;
  }

  // Returns the location of this object within subgraphs_, or
  // kInvalidSubgraphIndex if subgraphs_ is nullptr or *this is not
  // represented *subgraphs_.
  // WARNING: This is an experimental API and subject to
  // change.
  static constexpr int kInvalidSubgraphIndex = -1;
  int GetSubgraphIndex() const { return subgraph_index_; }

  // Returns true if this subgraph is the primary subgraph.
  // Returns false otherwise, including the cases when GetSubgraphIndex()
  // returns kInvalidSubgraphIndex.
  // WARNING: This is an experimental API and subject to change.
  bool IsPrimarySubgraph() const { return GetSubgraphIndex() == 0; }

  // True if all tensors in the graph has static size after calling
  // `AllocateTensors` function.
  // Before `AllocateTensors` is called, this will always return true;
  bool HasDynamicTensors() { return has_dynamic_tensors_; }

  // Assigns (or reassigns) a custom memory allocation for the given tensor.
  // `flags` is a bitmask, see TfLiteCustomAllocationFlags.
  // The runtime does NOT take ownership of the underlying memory.
  //
  // NOTE: User needs to call AllocateTensors() after this.
  // Invalid/insufficient buffers will cause an error during AllocateTensors or
  // Invoke (in case of dynamic shapes in the graph).
  //
  // Parameters should satisfy the following conditions:
  // 1. tensor->allocation_type == kTfLiteArenaRw or kTfLiteArenaRwPersistent
  //    In general, this is true for I/O tensors & variable tensors.
  // 2. allocation->data has the appropriate permissions for runtime access
  //    (Read-only for inputs, Read-Write for others), and outlives Interpreter.
  // 3. allocation->bytes >= tensor->bytes.
  //    This condition is checked again if any tensors are resized.
  // 4. allocation->data should be aligned to kDefaultTensorAlignment
  //    defined in lite/util.h. (Currently 64 bytes)
  //    This check is skipped if kTfLiteCustomAllocationFlagsSkipAlignCheck is
  //    set through `flags`.
  // TODO(b/182215910): Expand on this documentation in a g3doc.
  //
  // WARNING: This is an experimental interface that is subject to change.
  TfLiteStatus SetCustomAllocationForTensor(
      int tensor_index, const TfLiteCustomAllocation& allocation,
      int64_t flags = kTfLiteCustomAllocationFlagsNone);

  void SetName(const char* name);
  const std::string& GetName() const;

  // WARNING: This is an experimental API and subject to change.
  // Dumps debugging info by the underlying memory planner.
  // Note: to have minimal binary increase caused by this debug info dump for
  // the TfLite library and allow users to plug-in their own memory planner
  // debugger, we have utilized weak symbols to meet these two requirements. By
  // default, there is no debugging info dumped. However, if the TfLite-provided
  // lite:simple_memory_arena_debug_dump (i.e. containing the strong definition)
  // is linked to the program, calling this function will output memory usage
  // information about tenosrs and ops.
  void DumpMemoryPlannerDebugInfo() const;

  typedef struct SubgraphAllocInfo {
    size_t arena_size;
    size_t arena_persist_size;
    size_t dynamic_size;
    size_t resource_size;
  } SubgraphAllocInfo;

  // WARNING: This is an experimental API and subject to change.
  // Returns memory allocation status.
  void GetMemoryAllocInfo(SubgraphAllocInfo* alloc_info) const;

  // WARNING: This is an experimental API and subject to change.
  // Set the given `InterpreterOptions` object.
  void SetOptions(InterpreterOptions* options) {
    options_ = options;
    if (options && options->GetDynamicAllocationForLargeTensors() > 0) {
      // Note: this operation cannot be reversed.
      OptimizeMemoryForLargeTensors(
          options->GetDynamicAllocationForLargeTensors());
    }
  }

  // WARNING: This is an experimental API and subject to change.
  const InterpreterOptions* GetOptions() const { return options_; }

  // WARNING: This is an experimental API and subject to change.
  // True if all intermediates tensors should be preserved for debugging.
  bool ShouldPreserveAllTensors() const {
    return (options_ && options_->GetPreserveAllTensors());
  }

  // WARNING: This is an experimental API and subject to change.
  // True if all intermediate dynamic tensors should be released once they are
  // not used by the model.
  bool ShouldReleaseDynamicTensors() const {
    return (options_ && options_->GetEnsureDynamicTensorsAreReleased());
  }

  /// WARNING: This is an experimental API and subject to change.
  /// Use dynamic tensor allocation and deallocation method for large tensors
  /// instead of static memory planner. Dynamic tensors are allocated just
  /// before when they're needed and released when they're not needed anymore.
  /// It improves peak memory usage but there could be some latency impact. The
  /// parameter `large_tensors_thresholds_in_bytes` is used to determine large
  /// tensors. This API must be called before `AllocateTensors`.
  void OptimizeMemoryForLargeTensors(int large_tensors_thresholds_in_bytes);

  // WARNING: This is an experimental API and subject to change.
  // True if dynamic tensor allocation / deallocation method is enabled by
  // `OptimizeMemoryForLargeTensors` API.
  bool ShouldOptimizeMemoryForLargeTensors() {
    return (options_ && (options_->GetDynamicAllocationForLargeTensors() > 0));
  }

  // WARNING: This is an experimental API and subject to change.
  // Remove unused inputs of the subgraph. It checks usage of inputs and mark it
  // as kTfLiteOptionalTensor if the input is not used in graph execution.
  // Currently, it's used to remove unused inputs of WHILE cond subgraphs.
  TfLiteStatus RemoveUnusedInputs();

  // WARNING: This is an experimental API and subject to change.
  // If true, the graph-reordering optimization that finds a topological
  // reordering that keeps delegated nodes together will be disabled.
  bool DisableDelegateClustering() const {
    return (options_ && options_->GetDisableDelegateClustering());
  }

  // Retrieves the corresponding TfLiteContext of a subgraph given a subgraph
  // index and switches to the delegate context for this subgraph. If an invalid
  // subgraph index is given, returns kTfLiteError.
  // NOTE: This function is expected to be paired with ReleaseSubgraphContext()
  // once the delegate preparation is done and/or the delegate context functions
  // are no longer needed.
  TfLiteStatus AcquireSubgraphContext(int subgraph_index,
                                      TfLiteContext** acquired_context);
  // WARNING: This is an experimental interface that is subject to change.
  // Entry point for C node plugin API to acquire the subgraph context.
  static TfLiteStatus AcquireSubgraphContext(struct TfLiteContext* context,
                                             int subgraph_index,
                                             TfLiteContext** acquired_context);

  // Releases the subgraph context by switching back to the TFLite kernel
  // context for this specified subgraph.
  // NOTE: This function is expected to be used after AcquireSubgraphContext()
  // once the delegate preparation is done and/or the delegate context functions
  // are no longer needed.
  TfLiteStatus ReleaseSubgraphContext(int subgraph_index);
  // WARNING: This is an experimental interface that is subject to change.
  // Entry point for C node plugin API to release the subgraph context.
  static TfLiteStatus ReleaseSubgraphContext(struct TfLiteContext* context,
                                             int subgraph_index);

  // Marks the subgraph with the given index as "delegation-skippable". Returns
  // kTfLiteOk if the given subgraph index is valid and is successfully marked
  // as delegation-skippable, and an error status if the subgraph index is
  // invalid.
  // If a subgraph is delegation-skippable, then the subgraph will be handled by
  // a TfLiteDelegate (and that the delegate is supposed to be already aware of
  // this state), and therefore, TfLiteInterpreter can skip invoking
  // `ModifyGraphWithDelegate` on this subgraph.
  // NOTE: This function is expected to be called only when the subgraph that
  // `subgraph_index` is pointing to should be skipped by
  // interpreter::ModifyGraphWithDelegate (e.g. the subgraph is part of the list
  // of callee subgraphs of the same control flow node, and all of those callees
  // are supported by the same delegate at once).
  //
  // For example, this function can be used when the delegate is handling
  // control flow ops like while op. E.g. A while op has condition subgraph
  // indexed at `i` and body subgraph indexed at `j`. The op can be delegated
  // when the following condition satisfied:
  //   1. The delegate supports while op
  //   2. Both condition subgraph `i` and body subgraph `j` can be fully
  //      delegated by the delegate.
  // Then if the delegate decides to support the while node along with both body
  // and condition subgraphs, it should mark subgraphs `i` and `j` skippable so
  // those two subgraphs won't be delegated separately again after being
  // absorbed by the parent subgraph.
  // WARNING: It is the delegate's responsibility to define when to skip
  // subgraph->ModifyGraphWithDelegate, to check any edge cases (i.e. multiple
  // references to the subgraph that `subgraph_index` is pointing to), and to
  // mark that subgraph as skippable using this function.
  TfLiteStatus MarkSubgraphAsDelegationSkippable(int subgraph_index);

  // Returns whether this subgraph is delegation-skippable.
  // See the documentation on the private is_delegation_skippable_ field for
  // more details.
  bool IsDelegationSkippable() const { return is_delegation_skippable_; }

  // Marks this subgraph as delegation-skippable.
  // See the documentation on the private is_delegation_skippable_ field for
  // more details.
  // NOTE: This function is expected to be called only when this subgraph will
  // be skipped by the interpreter.
  void MarkAsDelegationSkippable() { is_delegation_skippable_ = true; }

  // Loads metadata of a TF Lite node's custom initialization data.
  // Specifically:
  // * Loads into the supplied 'fd' the file descriptor of the file that stores
  //   the 'node's custom  initialization data.  This output parameter will be
  //   loaded if the TF Lite runtime has access to the file descriptor, though
  //   this is not always the case, e.g. if a client provides a tflite::Model
  //   directly to the TF Lite runtime.  If 'fd' can be loaded then 'kTfLiteOk'
  //   will be returned, otherwise 'kTfLiteError' is returned.
  // * Loads into the supplied 'custom_initial_data_offset_in_file' pointer the
  //   offset of the 'node's custom init data in the file associated with 'fd'.
  //   This output parameter will be set to -1 if the 'node' does not have
  //   custom init data set.
  // * Loads into the supplied 'custom_initial_data_size' the size of the
  //   custom initialization data.  This output parameter will be set to -1 if
  //   the 'node' does not have custom init data set.
  //
  // Returns 'kTfLiteOk' when 'fd' has been loaded successfully and
  // 'kTfLiteError' otherwise.  Note that this means that 'kTfLiteOk' can be
  // returned, even if the 'node' does not have custom init data set.
  TfLiteStatus GetNodeInitDataMmapInfo(
      const TfLiteNode* node, int* fd,
      int64_t* custom_initial_data_offset_in_file,
      int64_t* custom_initial_data_size) const;

  // Returns true if the subgraph has delegates applied.
  bool HasDelegates();

  // Returns true if the subgraph has been fully delegated.
  bool IsFullyDelegated() const;

  const std::unordered_map<size_t, size_t>& GetTensorBufferIdentifiers() const {
    return tensor_buffer_identifiers_;
  }

  const std::unordered_map<size_t, size_t>& GetExternalTensorBufferIdentifiers()
      const {
    return tensor_external_buffer_ids_;
  }

  // Replaces the node for the given execution index with the subgraph.
  //
  // - The node and subgraph tensor counts must match.
  // - The subgraph index must be valid for the current interpreter object.
  //
  // The `last_inserted_execution_index` is updated to be the execution index of
  // the last node inserted in the execution plan (i.e. execution_index +
  // subgraph_execution_plan_size - 1).
  TfLiteStatus ReplaceNodeWithSubgraph(int execution_index,
                                       const TfLiteNode& node,
                                       int subgraph_index,
                                       int& last_inserted_execution_index);

  // Inlines the composite nodes that have not been taken by a delegate.
  TfLiteStatus InlineCompositeNodes();

 private:
#ifndef DOXYGEN_SKIP
  friend class tflite::impl::InterpreterBuilder;
  friend class tflite::async::AsyncSubgraph;
  friend class TestDelegate;
#endif  // DOXYGEN_SKIP
  // SubgraphAwareProfiler wraps an actual TFLite profiler, such as a
  // BufferedProfiler instance, and takes care of event profiling/tracing in a
  // certain subgraph.
  class SubgraphAwareProfiler : public Profiler {
   public:
    // Constructor should be called with the non-nullptr profiler argument.
    SubgraphAwareProfiler(Profiler* profiler, int64_t subgraph_index)
        : profiler_(profiler), subgraph_index_(subgraph_index) {}
    ~SubgraphAwareProfiler() override {}

    uint32_t BeginEvent(const char* tag, EventType event_type,
                        int64_t event_metadata1,
                        int64_t event_metadata2) override {
      if (!profiler_) return 0;
      return profiler_->BeginEvent(tag, event_type, event_metadata1,
                                   subgraph_index_);
    }

    void EndEvent(uint32_t event_handle) override {
      if (!profiler_) return;
      profiler_->EndEvent(event_handle);
    }

    void EndEvent(uint32_t event_handle, int64_t event_metadata1,
                  int64_t event_metadata2) override {
      if (!profiler_) return;
      profiler_->EndEvent(event_handle, event_metadata1, event_metadata2);
    }

    void AddEvent(const char* tag, EventType event_type, uint64_t elapsed_time,
                  int64_t event_metadata1, int64_t event_metadata2) override {
      if (!profiler_) return;
      profiler_->AddEvent(tag, event_type, elapsed_time, event_metadata1,
                          subgraph_index_);
    }

    void AddEventWithData(const char* tag, EventType event_type,
                          const void* data) override {
      if (!profiler_) return;
      profiler_->AddEventWithData(tag, event_type, data);
    }

   private:
    // Not own the memory.
    Profiler* const profiler_;
    const int64_t subgraph_index_;
  };

  // Ensure the internal node storage memory allocates at least `count`
  // spots for node. NOTE, this doesn't actually add operators. This is an
  // efficiency optimization that is subject to change.
  // Note: Only used during initialization.
  void ReserveNodes(int count);

  // Overrides execution plan. This bounds checks indices sent in.
  // Note: Only used during initialization.
  TfLiteStatus SetExecutionPlan(const std::vector<int>& new_plan);

  // Prevent 'context_' from accessing functions that are only available to
  // delegated kernels. Returns kTfLiteError if the counter violation happens,
  // i.e. if trying to switch to kernel context when it's already at kernel
  // context.
  TfLiteStatus SwitchToKernelContext();

  // Add delegate-only functions to 'context_'. Also increment the
  // `delegate_context_switch_count_` for each call. Returns kTfLiteError if the
  // count violation happens, i.e. if the counter goes below 0. This is not
  // expected to happen unless another function arbitrarily modify the counter.
  TfLiteStatus SwitchToDelegateContext();

  // Give 'op_reg' a chance to initialize itself using the contents of
  // 'buffer'. If registration_external is valid, use the 'init' callback from
  // that.
  void* OpInit(const TfLiteRegistration& op_reg, const char* buffer,
               size_t length);

  // Let 'op_reg' release any memory it might have allocated via 'OpInit'.
  // If registration_external is valid, use the 'free' callback from that.
  void OpFree(const TfLiteRegistration& op_reg, void* buffer);

  // Prepare the given 'node' for execution.
  TfLiteStatus OpPrepare(const TfLiteRegistration& op_reg, TfLiteNode* node);

  // Invoke the operator represented by 'node'.
  TfLiteStatus OpInvoke(const TfLiteRegistration& op_reg, TfLiteNode* node);

  // Call OpPrepare() for as many ops as possible, allocating memory for their
  // tensors. If an op containing dynamic tensors is found, preparation will be
  // postponed until this function is called again. This allows the interpreter
  // to wait until Invoke() to resolve the sizes of dynamic tensors.
  TfLiteStatus PrepareOpsAndTensors();

  // Call OpPrepare() for all ops starting at 'first_node'. Stop when a
  // dynamic tensors is found or all ops have been prepared. Fill
  // 'last_node_prepared' with the id of the op containing dynamic tensors, or
  // the last in the graph.
  TfLiteStatus PrepareOpsStartingAt(int first_execution_plan_index,
                                    const std::vector<int>& execution_plan,
                                    int* last_execution_plan_index_prepared);

  // Tensors needed by the interpreter. Use `AddTensors` to add more blank
  // tensor entries. Note, `tensors_.data()` needs to be synchronized to the
  // `context_` whenever this std::vector is reallocated. Currently this
  // only happens in `AddTensors()`.
  std::vector<TfLiteTensor> tensors_;

  // Check if an array of tensor indices are valid with respect to the Tensor
  // array.
  // NOTE: this changes consistent_ to be false if indices are out of bounds.
  TfLiteStatus CheckTensorIndices(const char* label, const int* indices,
                                  int length);

  // Check that the input indices and the output indices don't overlap.
  // This is needed because same tensor must not be used both as input and
  // output for an operator.
  // NOTE: this changes consistent_ to be false if indices are out of bounds.
  TfLiteStatus CheckInputAndOutputForOverlap(const int* input_indices,
                                             int num_inputs,
                                             const int* output_indices,
                                             int num_outputs);

  // Invoke the subgraph (run the whole graph in dependency order).
  // Does not report invoke status through profiler.
  TfLiteStatus InvokeImpl();

  // Allow a delegate to look at the graph and modify the graph to handle
  // parts of the graph themselves. After this is called, the graph may
  // contain new nodes that replace 1 more nodes.
  // Does not report invoke status through profiler.
  TfLiteStatus ModifyGraphWithDelegateImpl(TfLiteDelegate* delegate);

  // Request an tensor be resized implementation. If the given tensor is of
  // type kTfLiteDynamic it will also be allocated new memory.
  TfLiteStatus ResizeTensorImpl(TfLiteTensor* tensor, TfLiteIntArray* new_size);

  // Report a detailed error string (will be printed to stderr).
  void ReportErrorImpl(const char* format, va_list args);

  // Entry point for C node plugin API to request an tensor be resized.
  static TfLiteStatus ResizeTensor(TfLiteContext* context, TfLiteTensor* tensor,
                                   TfLiteIntArray* new_size);
  // Entry point for C node plugin API to report an error.
  static void ReportErrorC(TfLiteContext* context, const char* format, ...);

  // Entry point for C node plugin API to add new tensors.
  static TfLiteStatus AddTensors(TfLiteContext* context, int tensors_to_add,
                                 int* first_new_tensor_index);

  // WARNING: This is an experimental API and subject to change.
  // Entry point for C API ReplaceNodeSubsetsWithDelegateKernels
  // If the delegate has the 'opaque_delegate_builder' field set,
  // then the 'registration.registration_external' must be non-null,
  // and the subgraph takes ownership of the registration_external.
  // Ownership of 'nodes_to_replace' and 'delegate' remains with the caller.
  static TfLiteStatus ReplaceNodeSubsetsWithDelegateKernels(
      TfLiteContext* context, TfLiteRegistration registration,
      const TfLiteIntArray* nodes_to_replace, TfLiteDelegate* delegate);

  // Update the execution graph to replace some of the nodes with stub
  // nodes. Specifically any node index that has `nodes[index]==1` will be
  // slated for replacement with a delegate kernel specified by registration.
  // If the delegate has the 'opaque_delegate_builder' field set,
  // then the 'registration.registration_external' must be non-null,
  // and the subgraph takes ownership of the registration_external.
  // Ownership of 'nodes_to_replace' and 'delegate' remains with the caller.
  // WARNING: This is an experimental interface that is subject to change.
  TfLiteStatus ReplaceNodeSubsetsWithDelegateKernels(
      TfLiteRegistration registration, const TfLiteIntArray* nodes_to_replace,
      TfLiteDelegate* delegate);

  // Helper method for PreviewDelegatePartitioning and
  // ReplaceNodeSubsetsWithDelegateKernels. Creates node subsets whose members
  // are either all present in or all absent from *nodes_to_replace.  The
  // NodeSubsets and their members are in schedulable order, where
  // schedulability considers data dependencies and, if present, *control_edges_
  // between nodes.
  // If control_edges_ == nullptr, PartitionGraph will preserve the original
  // execuion order of nodes with OpMightHaveSideEffect() when finding
  // schedulable orderings.
  TfLiteStatus PartitionGraph(const TfLiteIntArray* nodes_to_replace,
                              std::vector<NodeSubset>* node_subsets);

  // WARNING: This is an experimental interface that is subject to change.
  // Gets the internal pointer to a TensorFlow lite node by node_index.
  TfLiteStatus GetNodeAndRegistration(int node_index, TfLiteNode** node,
                                      TfLiteRegistration** registration);

  // WARNING: This is an experimental interface that is subject to change.
  // Entry point for C node plugin API to get a node by index.
  static TfLiteStatus GetNodeAndRegistration(struct TfLiteContext*,
                                             int node_index, TfLiteNode** node,
                                             TfLiteRegistration** registration);

  // WARNING: This is an experimental interface that is subject to change.
  // Gets an TfLiteIntArray* representing the execution plan. The interpreter
  // owns this memory and it is only guaranteed to exist during the invocation
  // of the delegate prepare.
  TfLiteStatus GetExecutionPlan(TfLiteIntArray** execution_plan);

  // WARNING: This is an experimental interface that is subject to change.
  // Entry point for C node plugin API to get the execution plan.
  static TfLiteStatus GetExecutionPlan(struct TfLiteContext* context,
                                       TfLiteIntArray** execution_plan);

  // WARNING: This is an experimental interface that is subject to change.
  // Provides a preview of post-delegation partitioning. Each
  // TfLiteDelegateParams in the referenced array corresponds to one instance of
  // the delegate kernel.
  // nodes_to_replace should point to a valid array. partition_params_array &
  // num_partitions should be non-null.
  // Memory allocated by this method is automatically released with another call
  // to PreviewDelegateParitioning, or after TfLiteDelegate::Prepare is done.
  TfLiteStatus PreviewDelegatePartitioning(
      const TfLiteIntArray* nodes_to_replace,
      TfLiteDelegateParams** partition_params_array, int* num_partitions);

  // WARNING: This is an experimental interface that is subject to change.
  // Entry point for C node plugin API to preview delegation partitioning.
  static TfLiteStatus PreviewDelegatePartitioning(
      struct TfLiteContext* context, const TfLiteIntArray* nodes_to_replace,
      TfLiteDelegateParams** partition_params_array, int* num_partitions);

  // Retrieves named metadata from the TFLite model. Returns kTfLiteOk if
  // metadata is successfully obtained.
  // See the Metadata table in TFLite schema.
  TfLiteStatus GetModelMetadata(const char* name, const char** ptr,
                                size_t* bytes);

  // Entry point for C node plugin API to get model metadata based on name.
  static TfLiteStatus GetModelMetadata(const struct TfLiteContext* context,
                                       const char* name, const char** ptr,
                                       size_t* bytes);

  // Used to clear partitioning_preview_cache_, in case
  // PreviewDelegatePartitioning was called.
  void FreeDelegatePartitioningData();

  // Retrieve an existing external context by type.
  TfLiteExternalContext* GetExternalContext(TfLiteExternalContextType type);
  static TfLiteExternalContext* GetExternalContext(
      struct TfLiteContext* context, TfLiteExternalContextType type);

  // Set the value of an external context.
  static void SetExternalContext(struct TfLiteContext* context,
                                 TfLiteExternalContextType type,
                                 TfLiteExternalContext* ctx);

  // WARNING: This is an experimental API and subject to change.
  // Allow a delegate to look at the graph and modify the graph to handle
  // parts of the graph themselves. After this is called, the graph may
  // contain new nodes that replace 1 more nodes.
  // NOTE: If tensors were allocated prior to delegate application, they will
  // be reallocated if the graph was modified (i.e., the caller does *not* need
  // to explicitly call |AllocateTensors()| again). If tensors were unallocated,
  // they will remain unallocated after delegate application.
  // Returns one of the following status codes:
  // 1. kTfLiteOk: Delegation succeeded
  // 2. kTfLiteDelegateError: Delegation failed due to an error *in the
  // delegate*, or the delegate parameter was null. The Subgraph has been
  // restored to its pre-delegation state.
  // NOTE: This reverts all delegates previously applied to the Subgraph.
  // 3. kTfLiteApplicationError : Delegation failed to be applied due to the
  // incompatibility with the TF Lite runtime, e.g., the model graph is already
  // immutable when applying the delegate. However, the Subgraph is still in a
  // invokable state.
  // 4. kTfLiteUnresolvedOps: Delegation failed because the model has an
  // operator that cannot be resolved. This can happen when the op is not
  // registered or built with the TF Lite framework.
  // 5. kTfLiteError: Unexpected/runtime failure.
  TfLiteStatus ModifyGraphWithDelegate(TfLiteDelegate* delegate);

  // This un-applies all delegates that have been applied till now, but retains
  // pointers to them.
  // The old execution plan and nodes are restored.
  TfLiteStatus UndoAllDelegates();

  // This re-applies all delegates that were undone.
  // Does nothing if UndoAllDelegates wasn't previously called.
  TfLiteStatus RedoAllDelegates();

  // This removes all delegates.
  // The old execution plan and nodes are restored. The graph is invokable
  // afterwards.
  TfLiteStatus RemoveAllDelegates();

  // Cleanups up data reserved for the given node. Does not remove the {node,
  // registration} pair from nodes_and_registrations_.
  void CleanupNode(int node_index);

  // Ensures that `tensors_` has at least `kTensorsCapacityHeadroom` extra
  // capacity. Calling this function may invalidate existing pointers to
  // tensors. After calling this function, adding `kTensorsCapacityHeadroom`
  // more tensors won't invalidate the pointer to existing tensors.
  void EnsureTensorsVectorCapacity();

  // Ensures the memory required is planned and allocated.
  TfLiteStatus EnsureMemoryAllocations();

  enum class InliningStrategy { kNoAutoInline, kAutoInline };
  // Private version of AllocateTensors that allows disabling auto-inlining of
  // subgraphs.
  TfLiteStatus AllocateTensors(InliningStrategy auto_inline);

  // Enables cancellation of in flight invocation with `Cancel` call.
  // Should only be called by the interpreter when building the subgraph.
  // `flag` should be nullptr otherwise cancellation is disabled.
  TfLiteStatus EnableCancellation(std::atomic_flag* flag);

  // Attempts to cancel in flight invocation if any.
  // This will not affect `Invoke`s that happen after the cancellation.
  // Non blocking. Thread safe.
  // Returns kTfLiteError if cancellation is not enabled, otherwise returns
  // kTfLiteOk.
  TfLiteStatus Cancel();

  // Returns true if cancellation function returns true.
  bool IsCancelled();

  // Returns true if 'node' could have side effect (e.g. stateful op).
  // Note that any node that might update other tensors beside op's output
  // are considered to have side effect.
  // So control flow ops like 'If' and 'While' are considered to have
  // side effect because they can have ops that have side effect in the
  // condition and body subgraphs.
  bool OpMightHaveSideEffect(const TfLiteNode* node,
                             const TfLiteRegistration* registration) const;

  // Returns new GraphInfo object based on the current Subgraph.
  std::unique_ptr<GraphInfo> CreateGraphInfo();

  // Store a ptr to the model metadata owned by the Interpreter.
  // Since the lifetime of the Interpreter exceeds the Subgraph, metadata
  // remains valid for the latter's lifetime.
  // Also sets relevant fields on context_ based on known metadata.
  TfLiteStatus SetMetadata(const std::map<std::string, std::string>* metadata,
                           const ControlEdges* control_edges = nullptr);

  // Initializes the mapping between tensor index to the index of the
  // last operation that uses the tensor as input.
  void InitializeTensorReleaseMap();

  // May allocate dynamic tensor memory of node outputs. It's used when
  // `EnsureDynamicTensorsAreReleased` or`UseDynamicAllocationForLargeTensors`
  // API is used.
  TfLiteStatus MayAllocateOpOutput(TfLiteNode* node);

  // Checks the options for releasing dynamic tensors and release dynamic
  // tensors if configured.
  void MaybeReleaseDynamicTensors(const TfLiteNode& node, size_t node_index);

  // Set the buffer handle to a tensor.
  // The method is used to implement Interpreter::SetBufferHandle and
  // SignatureRunner::SetInputBufferHandle/SetOutputBufferHandle APIs.
  // `release_existing_buffer_handle`: If true, the existing buffer handle
  // will be released by TfLiteDelegate::FreeBufferHandle.
  static TfLiteStatus SetBufferHandleImpl(
      TfLiteContext* context, TfLiteTensor* tensor,
      TfLiteBufferHandle buffer_handle, TfLiteDelegate* delegate,
      bool release_existing_buffer_handle = true);

  // SetBufferHandleImpl with tensor index.
  TfLiteStatus SetBufferHandle(int tensor_index,
                               TfLiteBufferHandle buffer_handle,
                               TfLiteDelegate* delegate,
                               bool release_existing_buffer_handle = true) {
    return SetBufferHandleImpl(&context_, tensor(tensor_index), buffer_handle,
                               delegate, release_existing_buffer_handle);
  }

  // The state of the Subgraph.
  enum State {
    // The Subgraph isn't ready to be invoked.
    // `AllocateTensor` need to be called to enter an invokable state.
    kStateUninvokable = 0,
    // The Subgraph is ready to be invoked.
    kStateInvokable,
    // The Subgraph is ready to be invoked, and graph can't be further
    // modified. The Subgraph will enter this state when calling
    // `ModifyGraphWithDelegate` and the delegate doesn't support dynamic
    // tensors.
    kStateInvokableAndImmutable,
  };

  State state_ = kStateUninvokable;

  // A pure C data structure used to communicate with the pure C plugin
  // interface. To avoid copying tensor metadata, this is also the definitive
  // structure to store tensors.
  TfLiteContext context_ = {};

  // A pointer to the external contexts (kTfLiteMaxExternalContexts) array that
  // sits inside the associated TFLite interpreter instance.
  TfLiteExternalContext** external_contexts_;

  // A set of 'TfLiteOperator' pointers that are owned by the
  // subgraph.  The objects pointed to by the 'TfLiteOperator'
  // pointers are deleted in the 'Subgraph' destructor.
  //
  // The intended usage of this container is to provide (friend) classes
  // the option to dynamically allocate 'TfLiteOperator' objects
  // and then tie the lifetime of these objects to a subgraph.
  //
  // WARNING: This field needs to precede 'nodes_and_registration_', to ensure
  // that it outlives that field, since that field might contain references to
  // the TfLiteOperator objects contained in this fielld.
  //
  // LINT.IfChange
  // The definition of OperatorsCache implicitly assumes that
  // TfLiteOperatorDelete is the same as the standard C++ delete operator.
  // TODO(b/238435088): in op_resolver, include operator.h and use
  // 'TfLiteOperatorDelete' as the deleter, then we can eliminate
  // the IfChange...ThenChange directive below.
  std::shared_ptr<::tflite::internal::OperatorsCache> registration_externals_;
  // LINT.ThenChange(//tensorflow/lite/core/c/c_api.cc)

  // Node inputs/outputs are stored in TfLiteNode and TfLiteRegistration stores
  // function pointers to actual implementation.
  // Nodes should appear in the order in which they are instantiated at runtime.
  // Delegated nodes are appended after all the original ones.
  std::vector<std::pair<TfLiteNode, TfLiteRegistration>>
      nodes_and_registration_;

  // Whether the model is consistent. That is to say if the inputs and outputs
  // of every node and the global inputs and outputs are valid indexes into
  // the tensor array.
  bool consistent_ = true;

  // Array of indices representing the tensors that are inputs to the
  // interpreter.
  std::vector<int> inputs_;

  // Array of indices representing the tensors that are outputs to the
  // interpreter.
  std::vector<int> outputs_;

  // Array of indices representing the tensors that are variable tensors.
  std::vector<int> variables_;

  // The error reporter delegate that tflite will forward queries errors to.
  ErrorReporter* error_reporter_;

  // Index of the next node to prepare.
  // During Invoke(), Interpreter will allocate input tensors first, which are
  // known to be fixed size. Then it will allocate outputs from nodes as many
  // as possible. When there is a node that produces dynamic sized tensor.
  // Interpreter will stop allocating tensors, set the value of next allocate
  // node id, and execute the node to generate the output tensor before continue
  // to allocate successors. This process repeats until all nodes are executed.
  // NOTE: this relies on the order of nodes that is in topological order.
  int next_execution_plan_index_to_prepare_;

  // Only used in cases where a delegate supporting dynamic tensors is applied.
  // This helps prepare the original execution before the post-delegation one,
  // so that tensor shapes propagate.
  int next_original_execution_plan_index_to_prepare_;

  // This is similar to `next_execution_plan_index_to_prepare_`, but it tracks
  // which nodes' allocation is planned with the arena planner.
  //
  // This is a workaround for b/127354079. It shouldn't be necessary if
  // ArenaPlanner can "rewind" to a specific point.
  // TODO(b/127354079): Improve ArenaPlanner and remove this mechanism.
  int next_execution_plan_index_to_plan_allocation_;

  // WARNING: This is an experimental interface that is subject to change.
  // This is a list of node indices (to index into nodes_and_registration).
  // This represents a valid topological sort (dependency ordered) execution
  // plan. In particular, it is valid for this ordering to contain only a
  // subset of the node indices.
  std::vector<int> execution_plan_;

  // This is a copy of the first execution_plan_ before any delegates were
  // applied. It is empty if no delegates were applied to this Subgraph.
  std::vector<int> pre_delegation_execution_plan_;

  // Contains a list of delegates applied by the user so far, in order.
  std::vector<TfLiteDelegate*> delegates_applied_;

  // Set to true if UndoAllDelegates was called, and to false during
  // RedoAllDelegates.
  bool delegates_undone_ = false;

  // In the future, we'd like a TfLiteIntArray compatible representation.
  // TODO(aselle): replace execution_plan_ with this.
  IntArrayUniquePtr plan_cache_;

  // Used by PreviewDelegateParitioning.
  std::vector<TfLiteDelegateParams> partitioning_preview_cache_;

  std::unique_ptr<MemoryPlanner> memory_planner_;

  // Maps tensor index to custom allocation for all applicable tensors.
  std::map<int, TfLiteCustomAllocation> custom_allocations_;

  // Tracking bit for whether a tensor was resized in the course of an op
  // invocation. This is a useful hint to ensure that dynamic tensor outputs
  // trigger downstream reallocation after op invocation.
  bool tensor_resized_since_op_invoke_ = false;

  // Profiler for this interpreter instance.
  std::unique_ptr<SubgraphAwareProfiler> profiler_;

  // A pointer to vector of subgraphs. The vector is owned by the interpreter.
  std::vector<std::unique_ptr<Subgraph>>* subgraphs_ = nullptr;

  // Location of the pointer to *this in *subgraphs_, or kInvalidSubgraphIndex.
  const int subgraph_index_;

  // True if not all tensors in the graph has static size after calling
  // `PrepareOpsStartingAt` function (which is called by the `AllocateTensors`
  // public function).
  // The value is invalid before `PrepareOpStartingAt` is called.
  bool has_dynamic_tensors_ = true;

  // WARNING: This is an experimental interface that is subject to change.
  // This is the index of dynamic tensor which was checked at
  // PrepareOpsStartingAt() when `has_dynamic_tensors_` is set. This information
  // is kept only for user error message.
  int dynamic_tensor_index_ = -1;

  // Reference to cancellation function that can cancel a request in the middle
  // of a call to Invoke(). When this function returns True, a kTfLiteError is
  // thrown by Invoke().
  bool (*check_cancelled_func_)(void*) = nullptr;

  // Pointer to the cancellation flag owned by the interpreter.
  // If null, it means cancellation is not enabled.
  // If not null, in flight invocation will be cancelled if the flag is false.
  // The flag will be reset to true in the beginning of every `Invoke` call
  // so cancellation hapens before will not cancel subsequent invocations.
  std::atomic_flag* continue_invocation_ = nullptr;

  // Reference to data used by the cancellation function in
  // `check_cancelled_func_`.
  void* cancellation_data_ = nullptr;

  // A map of resources. Owned by interpreter and shared by multiple subgraphs.
  resource::ResourceMap* resources_ = nullptr;

  // A map of resources IDs. Owned by interpreter and shared by multiple
  // subgraphs.
  resource::ResourceIDMap* resource_ids_ = nullptr;

  // A map of initialization statuses, that indicate whether the intialization
  // subgraph invocation is done or not.
  resource::InitializationStatusMap* initialization_status_map_;

  // Name of the subgraph (analogous to function name).
  std::string name_;

  // Model-metadata owned by the Interpreter.
  const std::map<std::string, std::string>* metadata_ = nullptr;

  // Mapping between tensor index to the last index of the execution plan that
  // uses this tensor.
  std::map<int, int> tensor_to_last_op_index_;

  // `InterpreterOptions` object which is being used and owned by Interpreter.
  InterpreterOptions* options_;

  // Control edges (i.e., dependencies between nodes in addition to their data
  // dependencies); can be nullptr. Will be initialized from metadata associated
  // with the owning interpreter; the pointee is owned by the owning
  // interpreter. The owning interpreter will keep this consistent with
  // metadata_ by appropriately parametrized SetMetadata method calls.
  const ControlEdges* control_edges_ = nullptr;

  // Whether this subgraph is "delegation skippable". If a subgraph is
  // delegation-skippable, then the subgraph will be handled by a TfLiteDelegate
  // (and that the delegate is supposed to be already aware of this state), and
  // therefore, TfLiteInterpreter can skip invoking `ModifyGraphWithDelegate` on
  // this subgraph.
  bool is_delegation_skippable_ = false;

  // Count how many times the context has been switched to the delegate context.
  // Incremented during Acquire(), and decremented during Release().
  // Initialized to 1 initially because SwitchToKernelContext() is called once
  // during the Subgraph initialization.
  int delegate_context_switch_count_ = 1;

  /// The allocator used for holding memory of the model. Note that this will
  /// be null if the client provides a tflite::Model directly.
  const Allocation* allocation_ = nullptr;

  // Maps tensor constant buffers used in the subgraph to a model-wide
  // identifiers.
  std::unordered_map<size_t, size_t> tensor_buffer_identifiers_;

  // Maps tensor external buffer ids used in the subgraph to a model-wide
  // identifiers.
  std::unordered_map<size_t, size_t> tensor_external_buffer_ids_;
};

}  // namespace tflite
#endif  // TENSORFLOW_LITE_CORE_SUBGRAPH_H_
