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"""Dataclasses for learning rate schedule config."""
from typing import List, Optional

import dataclasses
from official.modeling.hyperparams import base_config


@dataclasses.dataclass
class ConstantLrConfig(base_config.Config):
  """Configuration for constant learning rate.

  This class is a containers for the constant learning rate decay configs.

  Attributes:
    name: The name of the learning rate schedule. Defaults to Constant.
    learning_rate: A float. The learning rate. Defaults to 0.1.
  """
  name: str = 'Constant'
  learning_rate: float = 0.1


@dataclasses.dataclass
class StepwiseLrConfig(base_config.Config):
  """Configuration for stepwise learning rate decay.

  This class is a container for the piecewise constant learning rate scheduling
  configs. It will configure an instance of PiecewiseConstantDecay keras
  learning rate schedule.

  An example (from keras docs): use a learning rate that's 1.0 for the first
  100001 steps, 0.5 for the next 10000 steps, and 0.1 for any additional steps.
    ```python
    boundaries: [100000, 110000]
    values: [1.0, 0.5, 0.1]

  Attributes:
    name: The name of the learning rate schedule. Defaults to PiecewiseConstant.
    boundaries: A list of ints of strictly increasing entries. Defaults to None.
    values: A list of floats that specifies the values for the intervals defined
      by `boundaries`. It should have one more element than `boundaries`.
            The learning rate is computed as follows: [0, boundaries[0]] ->
              values[0] [boundaries[0], boundaries[1]]     -> values[1]
              [boundaries[n-1], boundaries[n]]   -> values[n] [boundaries[n],
              end]               -> values[n+1] Defaults to None.
  """
  name: str = 'PiecewiseConstantDecay'
  boundaries: Optional[List[int]] = None
  values: Optional[List[float]] = None


@dataclasses.dataclass
class ExponentialLrConfig(base_config.Config):
  """Configuration for exponential learning rate decay.

  This class is a containers for the exponential learning rate decay configs.

  Attributes:
    name: The name of the learning rate schedule. Defaults to ExponentialDecay.
    initial_learning_rate: A float. The initial learning rate. Defaults to None.
    decay_steps: A positive integer that is used for decay computation. Defaults
      to None.
    decay_rate: A float. Defaults to None.
    staircase: A boolean, if true, learning rate is decreased at discreate
      intervals. Defaults to False.
  """
  name: str = 'ExponentialDecay'
  initial_learning_rate: Optional[float] = None
  decay_steps: Optional[int] = None
  decay_rate: Optional[float] = None
  staircase: Optional[bool] = None


@dataclasses.dataclass
class PolynomialLrConfig(base_config.Config):
  """Configuration for polynomial learning rate decay.

  This class is a containers for the polynomial learning rate decay configs.

  Attributes:
    name: The name of the learning rate schedule. Defaults to PolynomialDecay.
    initial_learning_rate: A float. The initial learning rate. Defaults to None.
    decay_steps: A positive integer that is used for decay computation. Defaults
      to None.
    end_learning_rate: A float.  The minimal end learning rate.
    power: A float.  The power of the polynomial. Defaults to linear, 1.0.
    cycle: A boolean, whether or not it should cycle beyond decay_steps.
      Defaults to False.
  """
  name: str = 'PolynomialDecay'
  initial_learning_rate: Optional[float] = None
  decay_steps: Optional[int] = None
  end_learning_rate: float = 0.0001
  power: float = 1.0
  cycle: bool = False


@dataclasses.dataclass
class CosineLrConfig(base_config.Config):
  """Configuration for Cosine learning rate decay.

  This class is a containers for the cosine learning rate decay configs,
  tf.keras.experimental.CosineDecay.

  Attributes:
    name: The name of the learning rate schedule. Defaults to CosineDecay.
    initial_learning_rate: A float. The initial learning rate. Defaults to None.
    decay_steps: A positive integer that is used for decay computation. Defaults
      to None.
    alpha: A float.  Minimum learning rate value as a fraction of
      initial_learning_rate.
  """
  name: str = 'CosineDecay'
  initial_learning_rate: Optional[float] = None
  decay_steps: Optional[int] = None
  alpha: float = 0.0


@dataclasses.dataclass
class DirectPowerLrConfig(base_config.Config):
  """Configuration for DirectPower learning rate decay.

  This class configures a schedule following follows lr * (step)^power.

  Attributes:
    name: The name of the learning rate schedule. Defaults to DirectPowerDecay.
    initial_learning_rate: A float. The initial learning rate. Defaults to None.
    power: A float. Defaults to -0.5, for sqrt decay.
  """
  name: str = 'DirectPowerDecay'
  initial_learning_rate: Optional[float] = None
  power: float = -0.5


@dataclasses.dataclass
class PowerAndLinearDecayLrConfig(base_config.Config):
  """Configuration for DirectPower learning rate decay.

  The schedule has the following behavoir.
  Let offset_step = step - offset.
  1) offset_step < 0, the actual learning rate equals initial_learning_rate.
  2) offset_step <= total_decay_steps * (1 - linear_decay_fraction), the
  actual learning rate equals lr * offset_step^power.
  3) total_decay_steps * (1 - linear_decay_fraction) <= offset_step <
  total_decay_steps, the actual learning rate equals lr * offset_step^power *
  (total_decay_steps - offset_step) / (total_decay_steps *
  linear_decay_fraction).
  4) offset_step >= total_decay_steps, the actual learning rate equals zero.

  Attributes:
    name: The name of the learning rate schedule. Defaults to
      PowerAndLinearDecay.
    initial_learning_rate: A float. The initial learning rate. Defaults to None.
    total_decay_steps: An int. The total number of steps for power + linear
      decay. Defaults to None.
    power: A float. The order of the polynomial. Defaults to -0.5, for sqrt
      decay.
    linear_decay_fraction: A float. In the last `linear_decay_fraction` steps,
      the learning rate will be multiplied by a linear decay. Defaults to 0.1.
    offset: An int. The offset applied to steps. Defaults to 0.
  """
  name: str = 'PowerAndLinearDecay'
  initial_learning_rate: Optional[float] = None
  total_decay_steps: Optional[int] = None
  power: float = -0.5
  linear_decay_fraction: float = 0.1
  offset: int = 0


@dataclasses.dataclass
class PowerDecayWithOffsetLrConfig(base_config.Config):
  """Configuration for power learning rate decay with step offset.

  Learning rate equals to `pre_offset_learning_rate` if `step` < `offset`.
  Otherwise, learning rate equals to lr * (step - offset)^power.

  Attributes:
    name: The name of the learning rate schedule. Defaults to
      PowerDecayWithOffset.
    initial_learning_rate: A float. The initial learning rate. Defaults to None.
    power: A float. Defaults to -0.5, for sqrt decay.
    offset: An integer. Power decay happens after `offset` steps.
    pre_offset_learning_rate: A float. The constant learning rate before
      `offset` steps.
  """
  name: str = 'PowerDecayWithOffset'
  initial_learning_rate: Optional[float] = None
  power: float = -0.5
  offset: int = 0
  pre_offset_learning_rate: float = 1.0e6


@dataclasses.dataclass
class LinearWarmupConfig(base_config.Config):
  """Configuration for linear warmup schedule config.

  This class is a container for the linear warmup schedule configs.
  Warmup_learning_rate is the initial learning rate, the final learning rate of
  the warmup period is the learning_rate of the optimizer in use. The learning
  rate at each step linearly increased according to the following formula:
    warmup_learning_rate = warmup_learning_rate +
    step / warmup_steps * (final_learning_rate - warmup_learning_rate).
  Using warmup overrides the learning rate schedule by the number of warmup
  steps.

  Attributes:
    name: The name of warmup schedule. Defaults to linear.
    warmup_learning_rate: Initial learning rate for the warmup. Defaults to 0.
    warmup_steps: Warmup steps. Defaults to None.
  """
  name: str = 'linear'
  warmup_learning_rate: float = 0
  warmup_steps: Optional[int] = None


@dataclasses.dataclass
class PolynomialWarmupConfig(base_config.Config):
  """Configuration for linear warmup schedule config.

  This class is a container for the polynomial warmup schedule configs.

  Attributes:
    name: The name of warmup schedule. Defaults to Polynomial.
    power: Polynomial power. Defaults to 1.
    warmup_steps: Warmup steps. Defaults to None.
  """
  name: str = 'polynomial'
  power: float = 1
  warmup_steps: Optional[int] = None
