# rlTRPOAgentOptions

## Description

Use an `rlTRPOAgentOptions`

object to specify options for trust
region policy optimization (TRPO) agents. To create a TRPO agent, use `rlTRPOAgent`

.

For more information on TRPO agents, see Trust Region Policy Optimization (TRPO) Agents.

For more information on the different types of reinforcement learning agents, see Reinforcement Learning Agents.

## Creation

### Description

creates an
`opt`

= rlTRPOAgentOptions`rlPPOAgentOptions`

object for use as an argument when creating a TRPO
agent using all default settings. You can modify the object properties using dot
notation.

sets option properties using
name-value arguments. For example,
`opt`

= rlTRPOAgentOptions(`Name,Value`

)`rlTRPOAgentOptions('DiscountFactor',0.95)`

creates an option set with
a discount factor of `0.95`

. You can specify multiple name-value
arguments. Enclose each property name in quotes.

## Properties

`ExperienceHorizon`

— Number of steps the agent interacts with the environment before learning

`512`

(default) | positive integer

Number of steps the agent interacts with the environment before learning from its
experience, specified as a positive integer. When the agent is trained in parallel,
`ExperienceHorizon`

is ignored, and the whole episode is used to
compute the gradients.

The `ExperienceHorizon`

value must be greater than or equal to
the `MiniBatchSize`

value.

`MiniBatchSize`

— Mini-batch size

`128`

(default) | positive integer

Mini-batch size used for each learning epoch, specified as a positive integer. When the agent uses a recurrent neural network, `MiniBatchSize`

is treated as the training trajectory length.

The `MiniBatchSize`

value must be less than or equal to the `ExperienceHorizon`

value.

`EntropyLossWeight`

— Entropy loss weight

`0.01`

(default) | scalar value between `0`

and `1`

Entropy loss weight, specified as a scalar value between `0`

and
`1`

. A higher entropy loss weight value promotes agent exploration by
applying a penalty for being too certain about which action to take. Doing so can help
the agent move out of local optima.

When gradients are computed during training, an additional gradient component is computed for minimizing the entropy loss. For more information, see Entropy Loss.

`NumEpoch`

— Number of epochs

`1`

(default) | positive integer

Number of epochs for which the actor and critic networks learn from the current experience set, specified as a positive integer.

`AdvantageEstimateMethod`

— Method for estimating advantage values

`"gae"`

(default) | `"finite-horizon"`

Method for estimating advantage values, specified as one of the following:

`"gae"`

— Generalized advantage estimator`"finite-horizon"`

— Finite horizon estimation

For more information on these methods, see the training algorithm information in Proximal Policy Optimization (PPO) Agents.

`GAEFactor`

— Smoothing factor for generalized advantage estimator

`0.95`

(default) | scalar value between `0`

and `1`

Smoothing factor for generalized advantage estimator, specified as a scalar value between `0`

and `1`

, inclusive. This option applies only when the `AdvantageEstimateMethod`

option is `"gae"`

`ConjugateGradientDamping`

— Conjugate gradient damping factor

`1e-4`

(default) | nonnegative scalar

Conjugate gradient damping factor for numerical stability, specified as a nonnegative scalar.

`KLDivergenceLimit`

— Upper limit for KL divergence

`0.01`

(default) | positive scalar

Upper limit for the Kullback-Leibler (KL) divergence between the old policy and the current policy, specified as a positive scalar.

`NumIterationsConjugateGradient`

— Maximum number of iterations for conjugate gradient decent

`10`

(default) | positive integer

Maximum number of iterations for conjugate gradient decent, specified as positive integer.

`NumIterationsLineSearch`

— Number of iterations for line search

`10`

(default) | positive integer

Number of iterations for line search, specified as a positive integer.

Typically, the default value works well for most cases.

`ConjugateGradientResidualTolerance`

— Conjugate gradient residual tolerance factor

`1e-8`

(default) | positive scalar

Conjugate gradient residual tolerance, specified as a positive scalar. Once the residual for the conjugate gradient algorithm is below this tolerance, the algorithm stops.

Typically, the default value works well for most cases.

`NormalizedAdvantageMethod`

— Method for normalizing advantage function

`"none"`

(default) | `"current`

| `"moving"`

Method for normalizing advantage function values, specified as one of the following:

`"none"`

— Do not normalize advantage values`"current"`

— Normalize the advantage function using the mean and standard deviation for the current mini-batch of experiences.`"moving"`

— Normalize the advantage function using the mean and standard deviation for a moving window of recent experiences. To specify the window size, set the`AdvantageNormalizingWindow`

option.

In some environments, you can improve agent performance by normalizing the advantage function during training. The agent normalizes the advantage function by subtracting the mean advantage value and scaling by the standard deviation.

`AdvantageNormalizingWindow`

— Window size for normalizing advantage function

`1e6`

(default) | positive integer

Window size for normalizing advantage function values, specified as a positive integer. Use this option when the `NormalizedAdvantageMethod`

option is `"moving"`

.

`CriticOptimizerOptions`

— Critic optimizer options

`rlOptimizerOptions`

object

Critic optimizer options, specified as an `rlOptimizerOptions`

object. It allows you to specify training parameters of
the critic approximator such as learning rate, gradient threshold, as well as the
optimizer algorithm and its parameters. For more information, see `rlOptimizerOptions`

and `rlOptimizer`

.

`SampleTime`

— Sample time of agent

`1`

(default) | positive scalar | `-1`

Sample time of agent, specified as a positive scalar or as `-1`

. Setting this
parameter to `-1`

allows for event-based simulations.

Within a Simulink^{®} environment, the RL Agent block
in which the agent is specified to execute every `SampleTime`

seconds
of simulation time. If `SampleTime`

is `-1`

, the
block inherits the sample time from its parent subsystem.

Within a MATLAB^{®} environment, the agent is executed every time the environment advances. In
this case, `SampleTime`

is the time interval between consecutive
elements in the output experience returned by `sim`

or
`train`

. If
`SampleTime`

is `-1`

, the time interval between
consecutive elements in the returned output experience reflects the timing of the event
that triggers the agent execution.

`DiscountFactor`

— Discount factor

`0.99`

(default) | positive scalar less than or equal to 1

Discount factor applied to future rewards during training, specified as a positive scalar less than or equal to 1.

## Object Functions

`rlTRPOAgent` | Trust region policy optimization (TRPO) reinforcement learning agent |

## Examples

### Create TRPO Agent Options Object

Create a TRPO agent options object, specifying the discount factor.

opt = rlTRPOAgentOptions(DiscountFactor=0.9)

opt = rlTRPOAgentOptions with properties: ExperienceHorizon: 512 MiniBatchSize: 128 EntropyLossWeight: 0.0100 NumEpoch: 3 AdvantageEstimateMethod: "gae" GAEFactor: 0.9500 ConjugateGradientDamping: 0.1000 KLDivergenceLimit: 0.0100 NumIterationsConjugateGradient: 10 NumIterationsLineSearch: 10 ConjugateGradientResidualTolerance: 1.0000e-08 NormalizedAdvantageMethod: "none" AdvantageNormalizingWindow: 1000000 CriticOptimizerOptions: [1x1 rl.option.rlOptimizerOptions] SampleTime: 1 DiscountFactor: 0.9000 InfoToSave: [1x1 struct]

You can modify options using dot notation. For example, set the agent sample time to `0.1`

.

opt.SampleTime = 0.1;

## Version History

**Introduced in R2021b**

### R2022a: Simulation and deployment: `UseDeterministicExploitation`

will be removed

The property `UseDeterministicExploitation`

of the
`rlTRPOAgentOptions`

object will be removed in a future release. Use the
`UseExplorationPolicy`

property of `rlTRPOAgent`

instead.

Previously, you set `UseDeterministicExploitation`

as follows.

Force the agent to always select the action with maximum likelihood, thereby using a greedy deterministic policy for simulation and deployment.

agent.AgentOptions.UseDeterministicExploitation = true;

Allow the agent to select its action by sampling its probability distribution for simulation and policy deployment, thereby using a stochastic policy that explores the observation space.

agent.AgentOptions.UseDeterministicExploitation = false;

Starting in R2022a, set `UseExplorationPolicy`

as follows.

Force the agent to always select the action with maximum likelihood, thereby using a greedy deterministic policy for simulation and deployment.

agent.UseExplorationPolicy = false;

Allow the agent to select its action by sampling its probability distribution for simulation and policy deployment, thereby using a stochastic policy that explores the observation space.

agent.UseExplorationPolicy = true;

Similarly to `UseDeterministicExploitation`

,
`UseExplorationPolicy`

affects only simulation and deployment; it does
not affect training.

## See Also

### Objects

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