tf_agents.bandits.agents.exp3_agent.Exp3Agent

An agent implementing the EXP3 bandit algorithm.

Inherits From: TFAgent

tf_agents.bandits.agents.exp3_agent.Exp3Agent(
    time_step_spec: tf_agents.typing.types.TimeStep,
    action_spec: tf_agents.typing.types.BoundedTensorSpec,
    learning_rate: float,
    name: Optional[Text] = None
)

Implementation based on

"Bandit Algorithms" Lattimore and Szepesvari, 2019 https://tor-lattimore.com/downloads/book/book.pdf

Args
time_step_spec	A TimeStep spec describing the expected TimeSteps.
action_spec	A scalar BoundedTensorSpec with int32 or int64 dtype describing the number of actions for this agent.
learning_rate	A float valued scalar. A higher value will force the agent to converge on a single action more quickly. A lower value will encourage more exploration. This value corresponds to the inverse_temperature argument passed to CategoricalPolicy.
name	a name for this instance of Exp3Agent.

Attributes
action_spec	TensorSpec describing the action produced by the agent.
collect_data_context
collect_data_spec	Returns a Trajectory spec, as expected by the collect_policy.
collect_policy	Return a policy that can be used to collect data from the environment.
data_context
debug_summaries
learning_rate
num_actions
policy	Return the current policy held by the agent.
summaries_enabled
summarize_grads_and_vars
time_step_spec	Describes the TimeStep tensors expected by the agent.
train_sequence_length	The number of time steps needed in experience tensors passed to train. Train requires experience to be a Trajectory containing tensors shaped [B, T, ...]. This argument describes the value of T required. For example, for non-RNN DQN training, T=2 because DQN requires single transitions. If this value is None, then train can handle an unknown T (it can be determined at runtime from the data). Most RNN-based agents fall into this category.
train_step_counter
training_data_spec	Returns a trajectory spec, as expected by the train() function.
weights

Methods

initialize

View source

initialize() -> Optional[tf.Operation]

Initializes the agent.

Returns
An operation that can be used to initialize the agent.

Raises
RuntimeError	If the class was not initialized properly (super.__init__ was not called).

loss

View source

loss(
    experience: tf_agents.typing.types.NestedTensor,
    weights: Optional[types.Tensor] = None,
    training: bool = False,
    **kwargs
) -> tf_agents.agents.tf_agent.LossInfo

Gets loss from the agent.

If the user calls this from _train, it must be in a tf.GradientTape scope in order to apply gradients to trainable variables. If intermediate gradient steps are needed, _loss and _train will return different values since _loss only supports updating all gradients at once after all losses have been calculated.

Args
experience	A batch of experience data in the form of a Trajectory. The structure of experience must match that of self.training_data_spec. All tensors in experience must be shaped [batch, time, ...] where time must be equal to self.train_step_length if that property is not None.
weights	(optional). A Tensor, either 0-D or shaped [batch], containing weights to be used when calculating the total train loss. Weights are typically multiplied elementwise against the per-batch loss, but the implementation is up to the Agent.
training	Explicit argument to pass to loss. This typically affects network computation paths like dropout and batch normalization.
**kwargs	Any additional data as args to loss.

Returns
A LossInfo loss tuple containing loss and info tensors.

Raises
RuntimeError	If the class was not initialized properly (super.__init__ was not called).

post_process_policy

View source

post_process_policy() -> tf_agents.policies.TFPolicy

Post process policies after training.

The policies of some agents require expensive post processing after training before they can be used. e.g. A Recommender agent might require rebuilding an index of actions. For such agents, this method will return a post processed version of the policy. The post processing may either update the existing policies in place or create a new policy, depnding on the agent. The default implementation for agents that do not want to override this method is to return agent.policy.

Returns
The post processed policy.

preprocess_sequence

View source

preprocess_sequence(
    experience: tf_agents.typing.types.NestedTensor
) -> tf_agents.typing.types.NestedTensor

Defines preprocess_sequence function to be fed into replay buffers.

This defines how we preprocess the collected data before training. Defaults to pass through for most agents. Structure of experience must match that of self.collect_data_spec.

Args
experience	a Trajectory shaped [batch, time, ...] or [time, ...] which represents the collected experience data.

Returns
A post processed Trajectory with the same shape as the input.

train

View source

train(
    experience: tf_agents.typing.types.NestedTensor,
    weights: Optional[types.Tensor] = None,
    **kwargs
) -> tf_agents.agents.tf_agent.LossInfo

Trains the agent.

Args
experience	A batch of experience data in the form of a Trajectory. The structure of experience must match that of self.training_data_spec. All tensors in experience must be shaped [batch, time, ...] where time must be equal to self.train_step_length if that property is not None.
weights	(optional). A Tensor, either 0-D or shaped [batch], containing weights to be used when calculating the total train loss. Weights are typically multiplied elementwise against the per-batch loss, but the implementation is up to the Agent.
**kwargs	Any additional data to pass to the subclass.

Returns
A LossInfo loss tuple containing loss and info tensors. In eager mode, the loss values are first calculated, then a train step is performed before they are returned. In graph mode, executing any or all of the loss tensors will first calculate the loss value(s), then perform a train step, and return the pre-train-step LossInfo.

Raises
RuntimeError	If the class was not initialized properly (super.__init__ was not called).