// Copyright 2020 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 schema defines how to configure TFLite for delegation. These
// definitions can be used in multiple ways: as output of a compatibility list,
// in benchmarking tools and to decouple delegate instantiation from code.
//
// The schema is work-in-progress, covering the most broadly used delegates and
// options.

syntax = "proto2";

package tflite.proto;

// ExecutionPreference is used to match accelerators against the preferences of
// the current application or usecase. Some of the values here can appear both
// in the compatibility list and as input, some only as input.
//
// These are separate from NNAPIExecutionPreference - the compatibility list
// design doesn't assume a one-to-one mapping between which usecases
// compatibility list entries have been developed for and what settings are used
// for NNAPI.
enum ExecutionPreference {
  // Match any selected preference. Allowlist (semantically - value is same as
  // on input).
  ANY = 0;
  // Match low latency preference. Both compatibility list and input.
  LOW_LATENCY = 1;
  // Math low power preference. Both compatibility list and input.
  LOW_POWER = 2;
  // Never accelerate. Can be used for input to compatibility list or for
  // standalone Acceleration configuration.
  FORCE_CPU = 3;
}

// TFLite accelerator to use.
enum Delegate {
  NONE = 0;

  NNAPI = 1;
  GPU = 2;
  HEXAGON = 3;
  XNNPACK = 4;
  // The EdgeTpu in Pixel devices.
  EDGETPU = 5;
  // The Coral EdgeTpu Dev Board / USB accelerator.
  EDGETPU_CORAL = 6;
}

enum NNAPIExecutionPreference {
  // Undefined.
  UNDEFINED = 0;
  // Prefer executing in a way that minimizes battery drain.
  NNAPI_LOW_POWER = 1;
  // Prefer returning a single answer as fast as possible, even if this causes
  // more power consumption.
  NNAPI_FAST_SINGLE_ANSWER = 2;
  // Prefer maximizing the throughput of successive frames, for example when
  // processing successive frames coming from the camera.
  NNAPI_SUSTAINED_SPEED = 3;
}

enum NNAPIExecutionPriority {
  NNAPI_PRIORITY_UNDEFINED = 0;
  NNAPI_PRIORITY_LOW = 1;
  NNAPI_PRIORITY_MEDIUM = 2;
  NNAPI_PRIORITY_HIGH = 3;
}

// One possible acceleration configuration.
message ComputeSettings {
  // Which preference to use this accelerator for.
  optional ExecutionPreference preference = 1;
  // How to configure TFLite
  optional TFLiteSettings tflite_settings = 2;
  // Identifiers to use for instrumentation and telemetry.
  optional string model_namespace_for_statistics = 3;
  optional string model_identifier_for_statistics = 4;
}

// NNAPI delegate settings.
message NNAPISettings {
  // Which instance (NNAPI accelerator) to use. One driver may provide several
  // accelerators (though a driver may also hide several back-ends behind one
  // name, at the choice of the driver vendor).
  // Note that driver introspection is only available in Android Q and later.
  optional string accelerator_name = 1;

  // NNAPI model compilation caching settings to be passed to
  // tflite::StatefulNnApiDelegate
  optional string cache_directory = 2;
  optional string model_token = 3;

  // NNAPI execution preference to pass. See
  // https://developer.android.com/ndk/reference/group/neural-networks.html
  optional NNAPIExecutionPreference execution_preference = 4;

  // Number of instances to cache for the same model (for input size
  // changes). This is mandatory for getting reasonable performance in that
  // case.
  optional int32 no_of_nnapi_instances_to_cache = 5;

  // Deprecated; use the fallback_settings in TFLiteSettings.
  //
  // Whether to automatically fall back to TFLite CPU path.
  optional FallbackSettings fallback_settings = 6 [deprecated = true];

  // Whether to allow use of NNAPI CPU (nnapi-reference accelerator) on Android
  // 10+ when an accelerator name is not specified. The NNAPI CPU typically
  // performs less well than the TfLite built-in kernels; but allowing allows a
  // model to be partially accelerated which may be a win.
  optional bool allow_nnapi_cpu_on_android_10_plus = 7;

  optional NNAPIExecutionPriority execution_priority = 8;

  // Whether to allow dynamic dimension sizes without re-compilation.
  // A tensor of with dynamic dimension must have a valid dims_signature
  // defined.
  // Only supported in NNAPI 1.1 and newer versions.
  // WARNING: Setting this flag to true may result in model being rejected by
  // accelerator. This should only be enabled if the target device supports
  // dynamic dimensions of the model.
  // By default this is set to false.
  optional bool allow_dynamic_dimensions = 9;

  // Whether to allow the NNAPI accelerator to optionally use lower-precision
  // float16 (16-bit floating point) arithmetic when doing calculations on
  // float32 (32-bit floating point).
  optional bool allow_fp16_precision_for_fp32 = 10;
}

// Which GPU backend to select. Default behaviour on Android is to try OpenCL
// and if it's not available fall back to OpenGL.
enum GPUBackend {
  UNSET = 0;
  OPENCL = 1;
  OPENGL = 2;
  // Not yet supported.
  // VULKAN = 3;
  // METAL = 4;
}

// GPU Delegate settings.
//
// See
// https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/delegates/gpu/delegate.h
message GPUSettings {
  optional bool is_precision_loss_allowed = 1;
  optional bool enable_quantized_inference = 2 [default = true];
  optional GPUBackend force_backend = 3;
  // TODO(b/152019007): add remaining options.
}

// Hexagon Delegate settings.
//
// See
// https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/delegates/hexagon/hexagon_delegate.h
message HexagonSettings {
  optional int32 debug_level = 1;
  optional int32 powersave_level = 2;
  optional bool print_graph_profile = 3;
  optional bool print_graph_debug = 4;
}

// XNNPack Delegate settings.
//
// See
// https://github.com/tensorflow/tensorflow/blob/master/tensorflow/lite/delegates/xnnpack/xnnpack_delegate.h
message XNNPackSettings {
  optional int32 num_threads = 1;
}

// EdgeTPU device spec.
//
message EdgeTpuDeviceSpec {
  // EdgeTPU platform types.
  enum PlatformType {
    MMIO = 0;
    REFERENCE = 1;
    SIMULATOR = 2;
    REMOTE_SIMULATOR = 3;
  }

  // Execution platform for the EdgeTPU device.
  optional PlatformType platform_type = 1;

  // Number of chips to use for the EdgeTPU device.
  optional int32 num_chips = 2;

  // Paths to the EdgeTPU devices;
  repeated string device_paths = 3;

  // Chip family used by the EdgeTpu device.
  optional int32 chip_family = 4;
}

// Generic definitions of EdgeTPU power states.
enum EdgeTpuPowerState {
  // Undefined power state.
  UNDEFINED_POWERSTATE = 0;

  // TPU core is off but control cluster is on.
  TPU_CORE_OFF = 1;

  // A non-active low-power state that has much smaller transition time to
  // active compared to off.
  READY = 2;

  // Minimum power active state.
  ACTIVE_MIN_POWER = 3;

  // Very low performance, very low power.
  ACTIVE_VERY_LOW_POWER = 4;

  // Low performance, low power.
  ACTIVE_LOW_POWER = 5;

  // The normal performance and power. This setting usually provides the
  // optimal perf/power trade-off for the average use-case.
  ACTIVE = 6;

  // Maximum performance level. Potentially higher power and thermal. This
  // setting may not be allowed in production depending on the system.
  OVER_DRIVE = 7;
}

message EdgeTpuInactivePowerConfig {
  // Inactive power states between inferences.
  optional EdgeTpuPowerState inactive_power_state = 1;

  // Inactive timeout in microseconds between inferences.
  optional int64 inactive_timeout_us = 2;
}

// EdgeTPU Delegate settings.
//
message EdgeTpuSettings {
  // Target inference power state for running the model.
  optional EdgeTpuPowerState inference_power_state = 1;

  // Inactive power states between inferences.
  repeated EdgeTpuInactivePowerConfig inactive_power_configs = 2;

  // Priority for the inference request.
  optional int32 inference_priority = 3 [default = -1];

  // Device spec for creating the EdgeTpu device.
  optional EdgeTpuDeviceSpec edgetpu_device_spec = 4;

  // A unique identifier of the input TfLite model.
  optional string model_token = 5;
}

// Coral Dev Board / USB accelerator delegate settings.
//
// See
// https://github.com/google-coral/edgetpu/blob/master/libedgetpu/edgetpu_c.h
message CoralSettings {
  enum Performance {
    UNDEFINED = 0;
    MAXIMUM = 1;
    HIGH = 2;
    MEDIUM = 3;
    LOW = 4;
  }

  // The Edge Tpu device to be used. See
  // https://github.com/google-coral/libcoral/blob/982426546dfa10128376d0c24fd8a8b161daac97/coral/tflite_utils.h#L131-L137
  optional string device = 1;
  // The desired performance level. This setting adjusts the internal clock
  // rate to achieve different performance / power balance. Higher performance
  // values improve speed, but increase power usage.
  optional Performance performance = 2 [default = MAXIMUM];
  // If true, always perform device firmware update (DFU) after reset. DFU is
  // usually only necessary after power cycle.
  optional bool usb_always_dfu = 3;
  // The maximum bulk in queue length. Larger queue length may improve USB
  // performance on the direction from device to host. When not specified (or
  // zero), `usb_max_bulk_in_queue_length` will default to 32 according to the
  // current EdgeTpu Coral implementation.
  optional int32 usb_max_bulk_in_queue_length = 4;
}

message CPUSettings {
  optional int32 num_threads = 1;
}

// How to configure TFLite.
message TFLiteSettings {
  // Which delegate to use.
  optional Delegate delegate = 1;

  // How to configure the chosen delegate.
  // (In principle we would like to use 'oneof', but flatc turns that into an
  // nested anonymous table rather than a union. See
  // https://github.com/google/flatbuffers/issues/4628).
  optional NNAPISettings nnapi_settings = 2;
  optional GPUSettings gpu_settings = 3;
  optional HexagonSettings hexagon_settings = 4;
  optional XNNPackSettings xnnpack_settings = 5;

  // How to configure CPU execution.
  optional CPUSettings cpu_settings = 6;

  // Shared delegation settings.
  optional int32 max_delegated_partitions = 7;

  // For configuring the EdgeTpuDelegate.
  optional EdgeTpuSettings edgetpu_settings = 8;

  // For configuring the Coral EdgeTpu Delegate.
  optional CoralSettings coral_settings = 10;

  // Whether to automatically fall back to TFLite CPU path.
  optional FallbackSettings fallback_settings = 9;
}

// Whether to automatically fallback to TFLite CPU path on delegation errors.
//
// Typically fallback is enabled in production use but disabled in tests and
// benchmarks to ensure they test the intended path.
message FallbackSettings {
  // Whether to allow automatically falling back to TfLite CPU path on
  // compilation failure. Default is not allowing automatic fallback.
  //
  // This is useful in naive production usecases where the caller would prefer
  // for the model to run even if it's not accelerated. More advanced users will
  // implement fallback themselves; e.g., by using a different model on CPU.
  //
  // Note that compilation errors may occur either at initial
  // ModifyGraphWithDelegate() time, or when calling AllocateTensors() after
  // resizing.
  optional bool allow_automatic_fallback_on_compilation_error = 7;
  // Whether to allow automatically falling back to TfLite CPU path on
  // execution error. Default is not allowing automatic fallback.
  //
  // Experimental, use with care (only when you have complete control over the
  // client code).
  //
  // The caveat above for compilation error holds.  Additionally, execution-time
  // errors are harder to handle automatically as they require invalidating the
  // TfLite interpreter which most client code has not been designed to deal
  // with.
  optional bool allow_automatic_fallback_on_execution_error = 8;
}

// On-device mini-benchmark result storage. The following definitions are used
// to keep an append-only log of benchmark results on-device. (Hence there is
// single top-level event that is used for all data).
//
// These definitions don't need a proto-to-flatbuffer conversion, since they are
// not used for specifying configuration in the Tasks library.

// Which stage of benchmarking the event is for.
// There might be multiple events with the same type, if a benchmark is run
// multiple times.
enum BenchmarkEventType {
  UNDEFINED_BENCHMARK_EVENT_TYPE = 0;
  // Benchmark start. A start without an end can be interpreted as a test that
  // has crashed or hung.
  START = 1;
  // Benchmarking completion. A model was successfully loaded, acceleration
  // configured and inference run without errors. There may still be an issue
  // with correctness of results, or with performance.
  END = 2;
  // Benchmark was not completed due to an error. The error may be a handled
  // error (e.g., failure in a delegate), or a crash.
  ERROR = 3;
  // Benchmark data has been sent for logging.
  LOGGED = 4;
}

// A correctness metric from a benchmark, for example KL-divergence between
// known-good CPU output and on-device output. These are primarily used for
// telemetry and monitored server-side.
message BenchmarkMetric {
  optional string name = 1;
  repeated float values = 2 [packed = true];
}

// Outcome of a successfully complete benchmark run. This information is
// intended to both be used on-device to select best compute configuration as
// well as sent to server for monitoring.
//
// Used with event type END.
message BenchmarkResult {
  // Time to load model and apply acceleration. Initialization may get run
  // multiple times to get information on variance.
  repeated int64 initialization_time_us = 1 [packed = true];
  // Time to run inference (call Invoke()). Inference may get run multiple times
  // to get information on variance.
  repeated int64 inference_time_us = 2 [packed = true];
  // Maximum memory used. Measures size of application heap (does not
  // necessarily take into account driver-side allocation.
  optional int32 max_memory_kb = 3;
  // Whether the inference produced correct results (validation graph output
  // 'ok' for all test inputs). Used on-device to disallow configurations that
  // produce incorrect results (e.g., due to OpenCL driver bugs).
  optional bool ok = 4;
  // Metrics that were used to determine the 'ok' status.
  repeated BenchmarkMetric metrics = 5;
}

// A handled error.
message ErrorCode {
  // Which delegate the error comes from (or NONE, if it comes from the tflite
  // framework).
  optional Delegate source = 1;
  // What the tflite level error is.
  optional int32 tflite_error = 2;
  // What the underlying error is (e.g., NNAPI or OpenGL error).
  optional int64 underlying_api_error = 3;
}

// When during benchmark execution an error occurred.
enum BenchmarkStage {
  UNKNOWN = 0;
  // During model loading or delegation.
  INITIALIZATION = 1;
  // During inference.
  INFERENCE = 2;
}

// An error that occurred during benchmarking.
//
// Used with event type ERROR.
message BenchmarkError {
  // How far benchmarking got.
  optional BenchmarkStage stage = 1;
  // Process exit code.
  optional int32 exit_code = 2;
  // Signal the process received.
  optional int32 signal = 3;
  // Handled error.
  repeated ErrorCode error_code = 4;
}

// Top-level benchmarking event stored on-device. All events for a model are
// parsed to detect the status.
message BenchmarkEvent {
  // Which settings were used for benchmarking.
  optional TFLiteSettings tflite_settings = 1;
  // Type of the event.
  optional BenchmarkEventType event_type = 2;
  // Result of benchmark, used when type is END.
  optional BenchmarkResult result = 3;
  // Error during benchmark, used when type is ERROR.
  optional BenchmarkError error = 4;
  // Start timestamps. These are used for
  // 1. Checking whether a test was started but not completed within a given
  // deadline.
  // 2. Optionally, telemetry timestamps.
  optional int64 boottime_us = 5;
  optional int64 wallclock_us = 6;
}
