rlDeterministicActorRepresentation

R2026b

(Not recommended) Deterministic actor representation for reinforcement learning agents

rlDeterministicActorRepresentation is not recommended. Use rlContinuousDeterministicActor instead. For more information, see rlDeterministicActorRepresentation is not recommended.

Description

This object implements a function approximator to be used as a deterministic actor within a reinforcement learning agent with a continuous action space. A deterministic actor takes observations as inputs and returns as outputs the action that maximizes the expected cumulative long-term reward, thereby implementing a deterministic policy. After you create an rlDeterministicActorRepresentation object, use it to create a suitable agent, such as an rlDDPGAgent agent. For more information on creating representations, see Create Actors, Critics, and Policy Objects.

Creation

Syntax

actor = rlDeterministicActorRepresentation(net,observationInfo,actionInfo,'Observation',obsName,'Action',actName)

actor = rlDeterministicActorRepresentation({basisFcn,W0},observationInfo,actionInfo)

actor = rlDeterministicActorRepresentation(___,options)

Description

actor = rlDeterministicActorRepresentation(net,observationInfo,actionInfo,'Observation',obsName,'Action',actName) creates a deterministic actor using the deep neural network net as approximator. actionInfo must specify a continuous action space, discrete action spaces are not supported. obsName must contain the names of the input layers of net that are associated with the observation specifications. The action names actName must be the names of the output layers of net that are associated with the action specifications.

actor = rlDeterministicActorRepresentation({basisFcn,W0},observationInfo,actionInfo) creates a deterministic actor using a custom basis function as underlying approximator. The first input argument is a two-elements cell in which the first element contains the handle basisFcn to a custom basis function, and the second element contains the initial weight matrix W0.

actor = rlDeterministicActorRepresentation(___,options) creates a deterministic actor using the additional options set options, which is an rlRepresentationOptions object. You can use this syntax with any of the previous input-argument combinations.

Input Arguments

net — Deep neural network

array of Layer objects | layerGraph object | DAGNetwork object | SeriesNetwork object | dlNetwork object

Deep neural network used as the underlying approximator within the actor, specified as one of the following:

• Array of Layer objects

• layerGraph object

• DAGNetwork object

• SeriesNetwork object

• dlnetwork object

The network input layers must be in the same order and with the same data type and dimensions as the signals defined in ObservationInfo. Also, the names of these input layers must match the observation names listed in obsName.

The network output layer must have the same data type and dimension as the signal defined in ActionInfo. Its name must be the action name specified in actName.

rlDeterministicActorRepresentation objects support recurrent deep neural networks.

For a list of deep neural network layers, see List of Deep Learning Layers. For more information on creating deep neural networks for reinforcement learning, see Create Actors, Critics, and Policy Objects.

obsName — Observation names

string | character vector | cell array of character vectors

Observation names, specified as a cell array of strings or character vectors. The observation names must be the names of the input layers in net.

Example: {'my_obs'}

actName — Action name

string | character vector | single-element cell array containing a character vector

Action name, specified as a single-element cell array that contains a character vector. It must be the name of the output layer of net.

Example: {'my_act'}

basisFcn — Custom basis function

function handle

Custom basis function, specified as a function handle to a user-defined MATLAB function. The user defined function can either be an anonymous function or a function on the MATLAB path. The action to be taken based on the current observation, which is the output of the actor, is the vector a = W'*B, where W is a weight matrix containing the learnable parameters and B is the column vector returned by the custom basis function.

When creating a deterministic actor representation, your basis function must have the following signature.

B = myBasisFunction(obs1,obs2, ...,obsN)

Here obs1 to obsN are observations in the same order and with the same data type and dimensions as the signals defined in observationInfo

Here, obs1 to obsN are inputs in the same order and with the same data type and initial dimensions as the environment observation channels defined in observationInfo. Since the training algorithm normally executes on batches of observations and actions at the same time, these inputs must also have an additional (last) batch dimension.

Example: @(obs1,obs2,obs3) [obs3(2,1,:)*obs1(1,1,:)^2; abs(obs2(5,1,:)+obs3(1,1:))]

W0 — Initial value of the basis function weights

column vector

Initial value of the basis function weights, W, specified as a matrix having as many rows as the length of the vector returned by the basis function and as many columns as the dimension of the action space.

Example: rand(2,1)

observationInfo — Observation specifications

rlFiniteSetSpec object | rlNumericSpec object | array

Observation specifications, specified as an rlFiniteSetSpec or rlNumericSpec object or an array containing any combination of such objects.

This argument sets the ObservationInfo property.

Example: rlNumericSpec([4 1])

actionInfo — Action specifications

rlNumericSpec object

Action specifications for a continuous action space, specified as an rlNumericSpec object.

This argument sets the ActionInfo property.

Example: rlNumericSpec([2 1])

options — Representation options

rlRepresentationOptions object

Representation options, specified as an rlRepresentationOptions object.

This argument sets the Options property.

Example: rlRepresentationOptions(LearnRate=1e-3)

Properties

Options — Representation options

rlRepresentationOptions object

Representation options, specified as an rlRepresentationOptions object. Available options include the optimizer used for training and the learning rate.

ObservationInfo — Observation specifications

rlFiniteSetSpec object | rlNumericSpec object | array

Observation specifications, specified as an rlFiniteSetSpec or rlNumericSpec object or an array of such objects. These objects define properties such as the dimensions, data types, and names of the observation signals.

rlDeterministicActorRepresentation sets the ObservationInfo property of actor to the input observationInfo.

You can extract ObservationInfo from an existing environment or agent using getObservationInfo. You can also construct the specifications manually.

ActionInfo — Action specifications

rlNumericSpec object

Action specifications for a continuous action space, specified as an rlNumericSpec object defining properties such as dimensions, data type and name of the action signals. The deterministic actor representation does not support discrete actions.

rlDeterministicActorRepresentation sets the ActionInfo property of actor to the input observationInfo.

You can extract ActionInfo from an existing environment or agent using getActionInfo. You can also construct the specification manually.

For custom basis function representations, the action signal must be a scalar, a column vector, or a discrete action.

Object Functions

rlDDPGAgent	Deep deterministic policy gradient (DDPG) reinforcement learning agent
rlTD3Agent	Twin-delayed deep deterministic (TD3) policy gradient reinforcement learning agent
getAction	Obtain action from agent, actor, or policy object given environment observations

Examples

Create Deterministic Actor from Deep Neural Network

Create an observation specification object (or alternatively use getObservationInfo to extract the specification object from an environment). For this example, define the observation space as a continuous four-dimensional space, so that a single observation is a column vector containing four doubles.

obsInfo = rlNumericSpec([4 1]);

Create an action specification object (or alternatively use getActionInfo to extract the specification object from an environment). For this example, define the action space as a continuous two-dimensional space, so that a single action is a column vector containing two doubles.

actInfo = rlNumericSpec([2 1]);

Create a deep neural network approximator for the actor. The input of the network (here called myobs) must accept a four-element vector (the observation vector just defined by obsInfo), and its output must be the action (here called myact) and be a two-element vector, as defined by actInfo.

net = [featureInputLayer(4,'Normalization','none','Name','myobs') 
    fullyConnectedLayer(2,'Name','myact')];

Create the critic with rlQValueRepresentation, using the network, the observations and action specification objects, as well as the names of the network input and output layers.

actor = rlDeterministicActorRepresentation(net,obsInfo,actInfo, ...
    'Observation',{'myobs'},'Action',{'myact'})

actor = 
  rlDeterministicActorRepresentation with properties:

         ActionInfo: [1x1 rl.util.rlNumericSpec]
    ObservationInfo: [1x1 rl.util.rlNumericSpec]
            Options: [1x1 rl.option.rlRepresentationOptions]

To check your actor, use getAction to return the action from a random observation, using the current network weights.

act = getAction(actor,{rand(4,1)}); act{1}

ans = 2x1 single column vector

   -0.5054
    1.5390

You can now use the actor to create a suitable agent (such as an rlACAgent, rlPGAgent, or rlDDPGAgent agent).

Create Deterministic Actor from Custom Basis Function

Create an observation specification object (or alternatively use getObservationInfo to extract the specification object from an environment). For this example, define the observation space as a continuous four-dimensional space, so that a single observation is a column vector containing 3 doubles.

obsInfo = rlNumericSpec([3 1]);

The deterministic actor does not support discrete action spaces. Therefore, create a continuous action space specification object (or alternatively use getActionInfo to extract the specification object from an environment). For this example, define the action space as a continuous two-dimensional space, so that a single action is a column vector containing 2 doubles.

actInfo = rlNumericSpec([2 1]);

Create a custom basis function. Each element is a function of the observations defined by obsInfo.

myBasisFcn = @(myobs) [myobs(2)^2; myobs(1); 2*myobs(2)+myobs(1); -myobs(3)]

myBasisFcn = function_handle with value:
    @(myobs)[myobs(2)^2;myobs(1);2*myobs(2)+myobs(1);-myobs(3)]

The output of the actor is the vector W'*myBasisFcn(myobs), which is the action taken as a result of the given observation. The weight matrix W contains the learnable parameters and must have as many rows as the length of the basis function output and as many columns as the dimension of the action space.

Define an initial parameter matrix.

W0 = rand(4,2);

Create the actor. The first argument is a two-element cell containing both the handle to the custom function and the initial weight matrix. The second and third arguments are, respectively, the observation and action specification objects.

actor = rlDeterministicActorRepresentation({myBasisFcn,W0},obsInfo,actInfo)

actor = 
  rlDeterministicActorRepresentation with properties:

         ActionInfo: [1x1 rl.util.rlNumericSpec]
    ObservationInfo: [1x1 rl.util.rlNumericSpec]
            Options: [1x1 rl.option.rlRepresentationOptions]

To check your actor, use the getAction function to return the action from a given observation, using the current parameter matrix.

a = getAction(actor,{[1 2 3]'});
a{1}

ans = 
  2x1 dlarray

    2.0595
    2.3788

You can now use the actor (along with a critic) to create a suitable continuous action space agent.

Create Deterministic Actor from Recurrent Neural Network

Create observation and action information. You can also obtain these specifications from an environment.

obsinfo = rlNumericSpec([4 1]);
actinfo = rlNumericSpec([2 1]);
numObs = obsinfo.Dimension(1);
numAct = actinfo.Dimension(1);

Create a recurrent deep neural network for the actor. To create a recurrent neural network, use a sequenceInputLayer as the input layer and include at least one lstmLayer.

net = [sequenceInputLayer(numObs,'Normalization','none','Name','state')
            fullyConnectedLayer(10,'Name','fc1')
            reluLayer('Name','relu1')
            lstmLayer(8,'OutputMode','sequence','Name','ActorLSTM')
            fullyConnectedLayer(20,'Name','CriticStateFC2')
            fullyConnectedLayer(numAct,'Name','action')
            tanhLayer('Name','tanh1')];

Create a deterministic actor representation for the network.

actorOptions = rlRepresentationOptions('LearnRate',1e-3,'GradientThreshold',1);
actor = rlDeterministicActorRepresentation(net,obsinfo,actinfo, ...
    'Observation',{'state'},'Action',{'tanh1'});

Version History

Introduced in R2020a

R2022a: rlDeterministicActorRepresentation is not recommended

rlDeterministicActorRepresentation is not recommended. Use rlContinuousDeterministicActor instead.

The following table shows some typical uses of rlDeterministicActorRepresentation, and how to update your code with rlContinuousDeterministicActor instead. The first table entry uses a neural network, the second one uses a basis function.

rlDeterministicActorRepresentation: Not Recommended	rlContinuousDeterministicActor: Recommended
myActor = rlDeterministicActorRepresentation(net,obsInfo,actInfo,'Observation',obsNames,'Action',actNames) with actInfo defining a continuous action space and net having observations as inputs and a single output layer with as many elements as the number of dimensions of the continuous action space.	myActor = rlContinuousDeterministicActor(net,obsInfo,actInfo,'ObservationInputNames',obsNames). Use this syntax to create a deterministic actor object with a continuous action space.
rep = rlDeterministicActorRepresentation({basisFcn,W0},obsInfo,actInfo), where the basis function has observations as inputs and actions as outputs, W0 is a matrix with as many columns as the number of possible actions, and actInfo defines a continuous action space.	rep = rlContinuousDeterministicActor({basisFcn,W0},obsInfo,actInfo). Use this syntax to create a deterministic actor object with a continuous action space.