Scikit-decide

# hub.solver.rtdp_bel.rtdp_bel

Domain specification

Domain

# RTDPBel

RTDP-Bel solver for Goal POMDPs.

From: Bonet & Geffner, "Solving POMDPs: RTDP-Bel vs. Point-based Algorithms", IJCAI 2009.

RTDP-Bel is RTDP applied to the belief MDP with discretized belief hashing. It performs trial-based search in belief space, where beliefs are probability distributions over physical states. Beliefs are discretized for hash table access using d(b(s)) = ceil(D * b(s)).

The default interface works with observations. The solver internally maintains and updates the current belief using Bayes rule from the observation history.

Uses cost minimization with goals over belief space.

# Constructor RTDPBel

RTDPBel(
  domain_factory: Callable[[], Domain],
  heuristic: Callable[[Domain, D.T_state], StrDict[Value[D.T_value]]] = <lambda function>,
  discretization: int = 10,
  time_budget: int = 3600000,
  rollout_budget: int = 100000,
  max_depth: int = 1000,
  epsilon: float = 0.001,
  discount: float = 1.0,
  parallel: bool = False,
  shared_memory_proxy = None,
  callback: Callable[[RTDPBel, Optional[int]], bool] = <lambda function>,
  verbose: bool = False
) -> None

Construct an RTDP-Bel solver instance.

# Parameters

  • domain_factory: Lambda function to create a domain instance.
  • heuristic: Function h(domain, state) -> Value returning the heuristic cost estimate for a physical state. The belief heuristic is computed as h(b) = sum_s b(s)*h(s). Defaults to Value(cost=0).
  • discretization: Discretization parameter D for belief hashing. d(b(s)) = ceil(D * b(s)). Higher D = finer discretization but more memory. Defaults to 10.
  • time_budget: Maximum solving time in milliseconds. Defaults to 3600000.
  • rollout_budget: Maximum number of trials. Defaults to 100000.
  • max_depth: Maximum depth of each trial. Defaults to 1000.
  • epsilon: Maximum Bellman residual for convergence. Defaults to 0.001.
  • discount: Value function's discount factor. Defaults to 1.0.
  • parallel: Parallelize trials. Defaults to False.
  • shared_memory_proxy: Optional shared memory proxy. Defaults to None.
  • callback: Function called at the end of each trial with (solver, thread_id). thread_id is None when running sequentially. Defaults to never stop. verbose: Whether to log verbose messages. Defaults to False.

# call_domain_method ParallelSolver

call_domain_method(
  self,
  name,
  *args
)

Calls a parallel domain's method. This is the only way to get a domain method for a parallel domain.

# check_domain Solver

check_domain(
  domain: Domain
) -> bool

Check whether a domain is compliant with this solver type.

By default, Solver.check_domain() provides some boilerplate code and internally calls Solver._check_domain_additional() (which returns True by default but can be overridden to define specific checks in addition to the "domain requirements"). The boilerplate code automatically checks whether all domain requirements are met.

# Parameters

  • domain: The domain to check.

# Returns

True if the domain is compliant with the solver type (False otherwise).

# close ParallelSolver

close(
  self
)

Joins the parallel domains' processes. Not calling this method (or not using the 'with' context statement) results in the solver forever waiting for the domain processes to exit.

# complete_with_default_hyperparameters Hyperparametrizable

complete_with_default_hyperparameters(
  kwargs: dict[str, Any],
  names: Optional[list[str]] = None
)

Add missing hyperparameters to kwargs by using default values

Args: kwargs: keyword arguments to complete (e.g. for __init__, init_model, or solve) names: names of the hyperparameters to add if missing. By default, all available hyperparameters.

Returns: a new dictionary, completion of kwargs

# copy_and_update_hyperparameters Hyperparametrizable

copy_and_update_hyperparameters(
  names: Optional[list[str]] = None,
  **kwargs_by_name: dict[str, Any]
) -> list[Hyperparameter]

Copy hyperparameters definition of this class and update them with specified kwargs.

This is useful to define hyperparameters for a child class for which only choices of the hyperparameter change for instance.

Args: names: names of hyperparameters to copy. Default to all. **kwargs_by_name: for each hyperparameter specified by its name, the attributes to update. If a given hyperparameter name is not specified, the hyperparameter is copied without further update.

Returns:

# get_belief_policy RTDPBel

get_belief_policy(
  self
) -> dict[frozenset[tuple[D.T_state, float]], tuple[StrDict[list[D.T_event]], float]]

Get the full belief-space policy as a dictionary.

Keys are frozensets of (state, probability) tuples representing discretized beliefs. Values are (action, value) tuples.

# get_default_hyperparameters Hyperparametrizable

get_default_hyperparameters(
  names: Optional[list[str]] = None
) -> dict[str, Any]

Get hyperparameters default values.

Args: names: names of the hyperparameters to choose. By default, all available hyperparameters will be suggested.

Returns: a mapping between hyperparameter's name_in_kwargs and its default value (None if not specified)

# get_domain ParallelSolver

get_domain(
  self
)

Returns the domain, optionally creating a parallel domain if not already created.

# get_domain_requirements Solver

get_domain_requirements(
) -> list[type]

Get domain requirements for this solver class to be applicable.

Domain requirements are classes from the skdecide.builders.domain package that the domain needs to inherit from.

# Returns

A list of classes to inherit from.

# get_explored_beliefs RTDPBel

get_explored_beliefs(
  self
) -> list[Distribution[D.T_state]]

Get the set of all explored belief nodes, each as a distribution over states.

# get_hyperparameter Hyperparametrizable

get_hyperparameter(
  name: str
) -> Hyperparameter

Get hyperparameter from given name.

# get_hyperparameters_by_name Hyperparametrizable

get_hyperparameters_by_name(
) -> dict[str, Hyperparameter]

Mapping from name to corresponding hyperparameter.

# get_hyperparameters_names Hyperparametrizable

get_hyperparameters_names(
) -> list[str]

List of hyperparameters names.

# get_nb_explored_beliefs RTDPBel

get_nb_explored_beliefs(
  self
) -> int

Get the number of belief nodes in the search graph.

# get_nb_rollouts RTDPBel

get_nb_rollouts(
  self
) -> int

Get the number of trials performed.

# get_next_action DeterministicPolicies

get_next_action(
  self,
  observation: StrDict[D.T_observation],
  domain: Optional[Domain] = None
) -> StrDict[list[D.T_event]]

Get the next deterministic action (from the solver's current policy).

# Parameters

  • observation: The observation for which next action is requested.
  • domain: the domain source of the observation. Typically used to get current applicable actions or action mask. NB: Be careful that the domain has not been autocast, so may not respect the T_domain specs.

# Returns

The next deterministic action.

# get_next_action_distribution UncertainPolicies

get_next_action_distribution(
  self,
  observation: StrDict[D.T_observation],
  domain: Optional[Domain] = None
) -> Distribution[StrDict[list[D.T_event]]]

Get the probabilistic distribution of next action for the given observation (from the solver's current policy).

# Parameters

  • observation: The observation to consider.
  • domain: the domain source of the observation. Typically used to get current applicable actions or action mask.

# Returns

The probabilistic distribution of next action.

# get_solving_time RTDPBel

get_solving_time(
  self
) -> int

Get the solving time in milliseconds.

# get_utility Utilities

get_utility(
  self,
  observation: StrDict[D.T_observation]
) -> D.T_value

Get the estimated on-policy utility of the given observation.

In mathematical terms, for a fully observable domain, this function estimates:

where is the current policy, any represents a trajectory sampled from the policy, is the return (cumulative reward) and the initial state for the trajectories.

# Parameters

  • observation: The observation to consider.

# Returns

The estimated on-policy utility of the given observation.

# get_utility_from_belief RTDPBel

get_utility_from_belief(
  self,
  belief: Distribution[D.T_state]
) -> D.T_value

Get the best value for an explicit belief state.

# is_policy_defined_for Policies

is_policy_defined_for(
  self,
  observation: StrDict[D.T_observation]
) -> bool

Check whether the solver's current policy is defined for the given observation.

# Parameters

  • observation: The observation to consider.

# Returns

True if the policy is defined for the given observation memory (False otherwise).

# reset Solver

reset(
  self
) -> None

Reset whatever is needed on this solver before running a new episode.

This function does nothing by default but can be overridden if needed (e.g. to reset the hidden state of a LSTM policy network, which carries information about past observations seen in the previous episode).

# reset_belief RTDPBel

reset_belief(
  self
) -> None

Reset the tracked belief to the initial belief from solve().

# sample_action Policies

sample_action(
  self,
  observation: StrDict[D.T_observation],
  domain: Optional[Domain] = None
) -> StrDict[list[D.T_event]]

Sample an action for the given observation (from the solver's current policy).

# Parameters

  • observation: The observation for which an action must be sampled.
  • domain: the domain source of the observation. Typically used to get current applicable actions or action mask.

# Returns

The sampled action.

# solve FromInitialState

solve(
  self,
  from_memory: Optional[Memory[D.T_state]] = None
) -> None

Run the solving process.

# Parameters

  • from_memory: The source memory (state or history) from which we begin the solving process. If None, initial state is used if the domain is initializable, else a ValueError is raised.

TIP

The nature of the solutions produced here depends on other solver's characteristics like policy and assessibility.

# solve_from FromAnyState

solve_from(
  self,
  memory: Memory[D.T_state]
) -> None

Run the solving process from a given state.

# Parameters

  • memory: The source memory (state or history) of the transition.

TIP

The nature of the solutions produced here depends on other solver's characteristics like policy and assessibility.

# suggest_hyperparameter_with_optuna Hyperparametrizable

suggest_hyperparameter_with_optuna(
  trial: optuna.trial.Trial,
  name: str,
  prefix: str,
  **kwargs
) -> Any

Suggest hyperparameter value during an Optuna trial.

This can be used during Optuna hyperparameters tuning.

Args: trial: optuna trial during hyperparameters tuning name: name of the hyperparameter to choose prefix: prefix to add to optuna corresponding parameter name (useful for disambiguating hyperparameters from subsolvers in case of meta-solvers) **kwargs: options for optuna hyperparameter suggestions

Returns:

kwargs can be used to pass relevant arguments to

  • trial.suggest_float()
  • trial.suggest_int()
  • trial.suggest_categorical()

For instance it can

  • add a low/high value if not existing for the hyperparameter or override it to narrow the search. (for float or int hyperparameters)
  • add a step or log argument (for float or int hyperparameters, see optuna.trial.Trial.suggest_float())
  • override choices for categorical or enum parameters to narrow the search

# suggest_hyperparameters_with_optuna Hyperparametrizable

suggest_hyperparameters_with_optuna(
  trial: optuna.trial.Trial,
  names: Optional[list[str]] = None,
  kwargs_by_name: Optional[dict[str, dict[str, Any]]] = None,
  fixed_hyperparameters: Optional[dict[str, Any]] = None,
  prefix: str
) -> dict[str, Any]

Suggest hyperparameters values during an Optuna trial.

Args: trial: optuna trial during hyperparameters tuning names: names of the hyperparameters to choose. By default, all available hyperparameters will be suggested. If fixed_hyperparameters is provided, the corresponding names are removed from names. kwargs_by_name: options for optuna hyperparameter suggestions, by hyperparameter name fixed_hyperparameters: values of fixed hyperparameters, useful for suggesting subbrick hyperparameters, if the subbrick class is not suggested by this method, but already fixed. Will be added to the suggested hyperparameters. prefix: prefix to add to optuna corresponding parameters (useful for disambiguating hyperparameters from subsolvers in case of meta-solvers)

Returns: mapping between the hyperparameter name and its suggested value. If the hyperparameter has an attribute name_in_kwargs, this is used as the key in the mapping instead of the actual hyperparameter name. the mapping is updated with fixed_hyperparameters.

kwargs_by_name[some_name] will be passed as **kwargs to suggest_hyperparameter_with_optuna(name=some_name)

# _check_domain_additional Solver

_check_domain_additional(
  domain: Domain
) -> bool

Check whether the given domain is compliant with the specific requirements of this solver type (i.e. the ones in addition to "domain requirements").

This is a helper function called by default from Solver.check_domain(). It focuses on specific checks, as opposed to taking also into account the domain requirements for the latter.

# Parameters

  • domain: The domain to check.

# Returns

True if the domain is compliant with the specific requirements of this solver type (False otherwise).

# _get_next_action DeterministicPolicies

_get_next_action(
  self,
  observation: StrDict[D.T_observation],
  domain: Optional[Domain] = None
) -> StrDict[list[D.T_event]]

Get the best action given an observation.

The solver internally maintains and updates the current belief using the last action returned and the new observation via Bayes rule. On the first call after solve(), the initial belief is used.

# _get_next_action_distribution UncertainPolicies

_get_next_action_distribution(
  self,
  observation: StrDict[D.T_observation],
  domain: Optional[Domain] = None
) -> Distribution[StrDict[list[D.T_event]]]

Get the probabilistic distribution of next action for the given observation (from the solver's current policy).

# Parameters

  • observation: The observation to consider.
  • domain: the domain source of the observation. Typically used to get current applicable actions or action mask. NB: Be careful that the domain has not been autocast, so may not respect the T_domain specs.

# Returns

The probabilistic distribution of next action.

# _get_next_action_from_belief RTDPBel

_get_next_action_from_belief(
  self,
  belief: Distribution[D.T_state]
) -> StrDict[list[D.T_event]]

Get the best action for an explicit belief state.

# _get_utility Utilities

_get_utility(
  self,
  observation: StrDict[D.T_observation]
) -> D.T_value

Get the estimated on-policy utility of the given observation.

In mathematical terms, for a fully observable domain, this function estimates:

where is the current policy, any represents a trajectory sampled from the policy, is the return (cumulative reward) and the initial state for the trajectories.

# Parameters

  • observation: The observation to consider.

# Returns

The estimated on-policy utility of the given observation.

# _initialize Solver

_initialize(
  self
)

Launches the parallel domains. This method requires to have previously recorded the self._domain_factory, the set of lambda functions passed to the solver's constructor (e.g. heuristic lambda for heuristic-based solvers), and whether the parallel domain jobs should notify their status via the IPC protocol (required when interacting with other programming languages like C++)

# _is_policy_defined_for Policies

_is_policy_defined_for(
  self,
  observation: StrDict[D.T_observation]
) -> bool

Check whether the solver's current policy is defined for the given observation.

# Parameters

  • observation: The observation to consider.

# Returns

True if the policy is defined for the given observation memory (False otherwise).

# _is_solution_defined_for_from_belief RTDPBel

_is_solution_defined_for_from_belief(
  self,
  belief: Distribution[D.T_state]
) -> bool

Check if a solution is defined for an explicit belief state.

# _reset Solver

_reset(
  self
) -> None

Reset whatever is needed on this solver before running a new episode.

This function does nothing by default but can be overridden if needed (e.g. to reset the hidden state of a LSTM policy network, which carries information about past observations seen in the previous episode).

# _sample_action Policies

_sample_action(
  self,
  observation: StrDict[D.T_observation],
  domain: Optional[Domain] = None
) -> StrDict[list[D.T_event]]

Sample an action for the given observation (from the solver's current policy).

# Parameters

  • observation: The observation for which an action must be sampled.
  • domain: the domain source of the observation. Typically used to get current applicable actions or action mask. NB: Be careful that the domain has not been autocast, so may not respect the T_domain specs.

# Returns

The sampled action.

# _solve FromInitialState

_solve(
  self,
  from_memory = None
) -> None

Run the solving process.

TIP

The nature of the solutions produced here depends on other solver's characteristics like policy and assessibility.

# _solve_from FromAnyState

_solve_from(
  self,
  initial_belief: Distribution[D.T_state]
) -> None

Run the solving process from a given state.

# Parameters

  • memory: The source memory (state or history) of the transition.

TIP

The nature of the solutions produced here depends on other solver's characteristics like policy and assessibility.