Source code for ggsolver.logic.base

import itertools
import logging
import spot
from dd.autoref import BDD
from ggsolver.logic.formula import BaseFormula, ParsingError
from tqdm import tqdm

import ggsolver.util as util
import ggsolver.models as models

[docs]class PL(BaseFormula): """ PL formula is internally represented as spot.formula instance. """ def __init__(self, f_str, atoms=None): super(PL, self).__init__(f_str, atoms) self._repr = spot.formula(f_str) if not self._repr.is_boolean(): raise ParsingError(f"Given formula:{f_str} is not a PL formula.") self._atoms = self._collect_atoms() def __str__(self): return str(self.f_str) def __eq__(self, other: BaseFormula): try: return spot.are_equivalent(self.f_str, other.f_str) except Exception: return False def _collect_atoms(self): atoms = set() def traversal(node: spot.formula, atoms_): if node.is_literal(): if "!" not in node.to_str(): atoms_.add(node.to_str()) return True return False self._repr.traverse(traversal, atoms) return self._atoms | atoms # ================================================================== # IMPLEMENTATION OF ABSTRACT METHODS # ==================================================================
[docs] def translate(self): """ Translate a propositional logic formula to an automaton. :return: (:class:`SpotAutomaton`) SpotAutomaton representing the automaton for PL formula. """ return SpotAutomaton(formula=self.f_str, atoms=self.atoms())
def substitute(self, subs_map=None): raise NotImplementedError("To be implemented in future.")
[docs] def evaluate(self, true_atoms): """ Evaluates a propositional logic formula given the set of true atoms. :param true_atoms: (Iterable[str]) A propositional logic formula. :return: (bool) True if formula is true, otherwise False. """ # Define a transform to apply to AST of spot.formula. def transform(node: spot.formula): if node.is_literal(): if "!" not in node.to_str(): if node.to_str() in true_atoms: return else: return spot.formula.ff() return # Apply the transform and return the result. # Since every literal is replaced by true or false, # the transformed formula is guaranteed to be either true or false. return True if transform(self._repr).is_tt() else False
[docs] def atoms(self): """ Gets the list of atoms associated with PL formula. The list may contain atoms that do not appear in the formula, if the user has provided it. :return: (List[str]) List of atoms. """ return self._atoms
# ================================================================== # SPECIAL METHODS OF PL CLASS # ==================================================================
[docs] def simplify(self): """ Simplifies a propositional logic formula. We use the `boolean_to_isop=True` option for `spot.simplify`. See :return: (str) String representing simplified formula. """ return spot.simplify(self._repr, boolean_to_isop=True).to_str()
[docs] def allsat(self): """ Generates the set of all satisfying assignments to atoms of the given propositional logic formula. .. note:: Complexity: Exponential in the number of atoms. """ # Apply limitation on atoms we allow in ggsolver. Raises ValueError if |atoms| exceeds limit. util.apply_atoms_limit(self.atoms()) # For each assignment, check whether the formula evaluates to True. # If yes, include it in set of all satisfying assignments. sat_assignments = [] for assignment in util.powerset(self.atoms()): if self.evaluate(assignment): sat_assignments.append(assignment) return sat_assignments
[docs]class Automaton(models.GraphicalModel): """ Represents an Automaton. .. math:: \\mathcal{A} = (Q, \\Sigma := 2^{AP}, \\delta, q_0, F) In the `Automaton` class, each component is represented as a function. - The set of states :math:`Q` is represented by `Automaton.states` function, - The set of atomic propositions :math:`AP` is represented by `Automaton.atoms` function, - The set of symbols :math:`\\Sigma` is represented by `Automaton.sigma` function, - The transition function :math:`\\delta` is represented by `` function, - The initial state :math:`q_0` is represented by `Automaton.init_state` function. An automaton may have one of the following acceptance conditions: - (:class:`Automaton.ACC_REACH`, 0) - (:class:`Automaton.ACC_SAFETY`, 0) - (:class:`Automaton.ACC_BUCHI`, 0) - (:class:`Automaton.ACC_COBUCHI`, 0) - (:class:`Automaton.ACC_PARITY`, 0) - (:class:`Automaton.ACC_PREF_LAST`, None) - (:class:`Automaton.ACC_ACC_PREF_MP`, None) """ NODE_PROPERTY = models.GraphicalModel.NODE_PROPERTY.copy() EDGE_PROPERTY = models.GraphicalModel.EDGE_PROPERTY.copy() GRAPH_PROPERTY = models.GraphicalModel.GRAPH_PROPERTY.copy() ACC_REACH = "Reach" #: ACC_SAFETY = "Safety" #: ACC_BUCHI = "Buchi" #: ACC_COBUCHI = "co-Buchi" #: ACC_PARITY = "Parity Min Even" #: ACC_PREF_LAST = "Preference Last" #: ACC_PREF_MP = "Preference MostPreferred" #: ACC_UNDEFINED = "undefined" ACC_TYPES = [ ACC_UNDEFINED, ACC_REACH, ACC_SAFETY, ACC_BUCHI, ACC_COBUCHI, ACC_PARITY, ACC_PREF_LAST, ACC_PREF_MP ] #: Acceptance conditions supported by Automaton.
[docs] def __init__(self, **kwargs): """ Supported keyword arguments: :param states: (Iterable) An iterable over states in the automaton. :param atoms: (Iterable[str]) An iterable over atomic propositions in the automaton. :param trans_dict: (dict) A dictionary defining the (deterministic) transition function of automaton. Format of dictionary: {state: {logic.PLFormula: state}} :param init_state: (object) The initial state, a member of states iterable. :param final: (Iterable[states]) The set of final states, a subset of states iterable. :param acc_cond: (tuple) A tuple of automaton acceptance type and an acceptance set. For example, DFA has an acceptance condition of `(Automaton.ACC_REACH, 0)`. :param is_deterministic: (bool) Whether the Automaton is deterministic. """ kwargs["input_domain"] = "atoms" if "input_domain" not in kwargs else kwargs["input_domain"] super(Automaton, self).__init__(**kwargs) # Process keyword arguments if "states" in kwargs: def states_(): return list(kwargs["states"]) self.states = states_ if "atoms" in kwargs: def atoms_(): return list(kwargs["atoms"]) self.atoms = atoms_ if "trans_dict" in kwargs: def delta_(state, inp): next_states = set() for formula, n_state in kwargs["trans_dict"][state].items(): if PL(f_str=formula, atoms=self.atoms()).evaluate(inp): next_states.add(n_state) if self.is_deterministic(): if len(next_states) > 1: raise ValueError("Non-determinism detected in a deterministic automaton. " + f"delta({state}, {inp}) -> {next_states}.") return next(iter(next_states), None) if len(next_states) == 1 else None return next_states = delta_ if "init_state" in kwargs: self.initialize(kwargs["init_state"]) if "final" in kwargs: def final_(state): return [0] if state in kwargs["final"] else [-1] = final_ if "acc_cond" in kwargs: def acc_cond_(): return kwargs["acc_cond"] self.acc_cond = acc_cond_ if "is_deterministic" in kwargs: def is_deterministic_(): return kwargs["is_deterministic"] self.is_deterministic = is_deterministic_
# ========================================================================== # PRIVATE FUNCTIONS # ========================================================================== def _gen_underlying_graph_unpointed(self, graph): """ Programmer's notes: 1. Caches states (returned by `self.states()`) in self.__states variable. 2. Assumes all states to be hashable. 3. Parallel edges are merged using ORing of PL Formulas. """ # Get states states = getattr(self, "states") states = list(states()) # Add states to graph node_ids = list(graph.add_nodes(len(states))) # Cache states as a dictionary {state: uid} self.__states = dict(zip(states, node_ids)) # Node property: state np_state = graph.NodePropertyMap(graph=graph) np_state.update(dict(zip(node_ids, states))) graph["state"] = np_state # Logging and printing"[INFO] Processed node property: states. Added {len(node_ids)} states. [OK]")) # Get input function # Specialized for automaton class: we expect input function to be atoms. assert self._input_domain == "atoms", "For automaton class, we expect input domain to be `atoms`. " \ f"Currently it is set to '{self._input_domain}'." input_func = getattr(self, self._input_domain) atoms = input_func() inputs = util.powerset(atoms)"[INFO] Input domain function detected as '{self._input_domain}'. [OK]")) # Graph property: input domain (stores the name of edge property that represents inputs) graph["input_domain"] = self._input_domain"[INFO] Processed graph property: input_domain. [OK]")) # # Get input domain # inputs = input_func() # Edge properties: input, prob, ep_input = graph.EdgePropertyMap(graph=graph) ep_prob = graph.EdgePropertyMap(graph=graph, default=None) # Generate edges delta = getattr(self, "delta") edges = {uid: dict() for uid in node_ids} for state, inp in tqdm(itertools.product(self.__states.keys(), inputs), total=len(self.__states) * 2 ** len(atoms), desc="Specialized unpointed graphify adding edges for automaton "): new_edges = self._gen_edges(delta, state, inp) # Update graph edges uid = self.__states[state] for _, t, _, _ in new_edges: vid = self.__states[t] if vid not in edges[uid]: edges[uid][vid] = list() edges[uid][vid].append(inp) for uid in edges.keys(): for vid in edges[uid].keys(): key = graph.add_edge(uid, vid) ep_input[uid, vid, key] = sat2formula(atoms, edges[uid][vid]) ep_prob[uid, vid, key] = None # Add edge properties to graph graph["input"] = ep_input graph["prob"] = ep_prob"[INFO] Processed edge property: input. [OK]"))"[INFO] Processed graph property: prob. [OK]")) def _gen_underlying_graph_pointed(self, graph): raise NotImplementedError("Pointed graphify is not defined for automaton.") # ========================================================================== # FUNCTIONS TO BE IMPLEMENTED BY USER. # ==========================================================================
[docs] @models.register_property(GRAPH_PROPERTY) def atoms(self): """ Returns a list/tuple of atomic propositions. :return: (list of str) A list of atomic proposition. """ raise NotImplementedError(f"{self.__class__.__name__}.atoms() is not implemented.")
[docs] @models.register_property(NODE_PROPERTY) def final(self, state): """ Returns the acceptance set associated with the given state. :param state: (an element of `self.states()`) A valid state. :return: (int) Acceptance set associated with the given state. """ raise NotImplementedError(f"{self.__class__.__name__}.final() is not implemented.")
[docs] @models.register_property(GRAPH_PROPERTY) def acc_type(self): """ Acceptance type of the automaton. :return: A value from :class:`Automaton.ACC_TYPES`. """ return self.acc_cond()[0]
[docs] @models.register_property(GRAPH_PROPERTY) def acc_cond(self): """ Acceptance condition of the automaton. :return: (2-tuple) A value of type (acc_type, acc_set) where acc_type is from :class:`Automaton.ACC_TYPES` and acc_set is either an integer or a list of integer. """ return self.ACC_UNDEFINED, None
[docs] @models.register_property(GRAPH_PROPERTY) def num_acc_sets(self): """ Number of acceptance sets. """ raise NotImplementedError(f"{self.__class__.__name__}.num_acc_sets() is not implemented.")
[docs] @models.register_property(GRAPH_PROPERTY) def is_complete(self): """ Is the automaton complete? That is, is transition function well-defined at every state for any input symbol? """ raise NotImplementedError
# ========================================================================== # FUNCTIONS TO BE IMPLEMENTED BY USER. # ==========================================================================
[docs] def sigma(self): """ Returns the set of alphabet of automaton. It is the powerset of atoms(). """ return list(util.powerset(self.atoms()))
[docs] def from_automaton(self, aut: 'Automaton'): """ Constructs an Automaton from another Automaton instance. The input automaton's acceptance condition must match that of a current Automaton. """ assert aut.acc_cond() == self.acc_cond(), f"aut.acc_cond(): {aut.acc_cond()}, self.acc_cond(): {self.acc_cond()}" # Copy all functions from automaton. self.states = aut.states = self._input_domain = "atoms" for gp in aut.GRAPH_PROPERTY: setattr(self, gp, getattr(aut, gp)) for np in aut.NODE_PROPERTY: setattr(self, np, getattr(aut, np)) for ep in aut.EDGE_PROPERTY: setattr(self, ep, getattr(aut, ep))
[docs]class SpotAutomaton(Automaton): """ `SpotAutomaton` constructs an :class:`Automaton` from an LTL specification string using `spot` ( with customizations for `ggsolver`. **Customizations:** Since `ggsolver` contains several algorithms for reactive/controller synthesis, we prefer to construct deterministic automata. Given an LTL formula, `SpotAutomaton` automatically determines the best acceptance condition that would result in a deterministic automaton.. Programmer's note: The graphified version of automaton does not use PL formulas as edge labels. This is intentionally done to be able to run our codes on robots that may not have logic libraries installed. """ def __init__(self, formula=None, options=None, atoms=None): """ Given an LTL formula, SpotAutomaton determines the best options for spot.translate() function to generate a deterministic automaton in ggsolver.Automaton format. :param formula: (str) LTL formula. :param options: (List/Tuple of str) Valid options for spot.translate() function. By default, the value is `None`, in which case, the options are determined automatically. See description below. **Default translation options:** While constructing an automaton using `spot`, we use the following options: `deterministic, high, complete, unambiguous, SBAcc`. If selected acceptance condition is parity, then we use `colored` option as well. The default options can be overriden. For quick reference, the following description is copied from `spot` documentation ( The optional arguments should be strings among the following: - at most one in 'GeneralizedBuchi', 'Buchi', or 'Monitor', 'generic', 'parity', 'parity min odd', 'parity min even', 'parity max odd', 'parity max even', 'coBuchi' (type of acceptance condition to build) - at most one in 'Small', 'Deterministic', 'Any' (preferred characteristics of the produced automaton) - at most one in 'Low', 'Medium', 'High' (optimization level) - any combination of 'Complete', 'Unambiguous', 'StateBasedAcceptance' (or 'SBAcc' for short), and 'Colored' (only for parity acceptance) """ # Construct the automaton super(SpotAutomaton, self).__init__(input_domain="atoms") # Instance variables self._formula = formula self._user_atoms = set(atoms) if atoms is not None else set() # If options are not given, determine the set of options to generate deterministic automaton with # state-based acceptance condition. if options is None: options = self._determine_options() print(f"[INFO] Translating {self._formula} with options={options}.") self.spot_aut = spot.translate(formula, *options) # Set the acceptance condition (in ggsolver terms) name = self.spot_aut.acc().name() if name == "Büchi" and spot.mp_class(formula).upper() in ["B", "S"]: self._acc_cond = (Automaton.ACC_SAFETY, 0) elif name == "Büchi" and spot.mp_class(formula).upper() in ["G"]: self._acc_cond = (Automaton.ACC_REACH, 0) elif name == "Büchi" and spot.mp_class(formula).upper() in ["O", "R"]: self._acc_cond = (Automaton.ACC_BUCHI, 0) elif name == "co-Büchi": self._acc_cond = (Automaton.ACC_COBUCHI, 0) elif name == "all": self._acc_cond = (Automaton.ACC_SAFETY, 0) else: # name contains "parity": self._acc_cond = (Automaton.ACC_PARITY, 0) def _determine_options(self): """ Determines the options based on where the given LTL formula lies in Manna-Pnueli hierarchy. """ mp_cls = spot.mp_class(self.formula()) if mp_cls.upper() == "B" or mp_cls.upper() == "S": return 'Monitor', "Deterministic", "High", "Complete", "Unambiguous", "SBAcc" elif mp_cls.upper() == "G" or mp_cls.upper() == "O" or mp_cls.upper() == "R": return 'Buchi', "Deterministic", "High", "Complete", "Unambiguous", "SBAcc" elif mp_cls.upper() == "P": return 'coBuchi', "Deterministic", "High", "Complete", "Unambiguous", "SBAcc" else: # cls.upper() == "T": return 'parity min even', "Deterministic", "High", "Complete", "Unambiguous", "SBAcc", "colored"
[docs] def states(self): """ States of automaton. """ return list(range(self.spot_aut.num_states()))
[docs] def atoms(self): """ Atomic propositions appearing in LTL formula. """ return list({str(ap) for ap in self.spot_aut.ap()} | self._user_atoms)
[docs] def delta(self, state, inp): """ Transition function of automaton. For a deterministic automaton, returns a single state. Otherwise, returns a list/tuple of states. :param state: (object) A valid state. :param inp: (list) List of atoms that are true (an element of sigma). """ # Preprocess inputs inp_dict = {p: True for p in inp} | {p: False for p in self.atoms() if p not in inp} # Initialize a BDD over set of atoms. bdd = BDD() bdd.declare(*self.atoms()) # Get spot BDD dict to extract formula bdd_dict = self.spot_aut.get_dict() # Get next states next_states = [] for t in self.spot_aut.out(state): label = spot.bdd_format_formula(bdd_dict, t.cond) label = spot.formula(label) if label.is_ff(): continue elif label.is_tt(): next_states.append(int(t.dst)) else: label = spot.formula(label).to_str('spin') v = bdd.add_expr(label) if bdd.let(inp_dict, v) == bdd.true: next_states.append(int(t.dst)) # Return based on whether automaton is deterministic or non-deterministic. # If automaton is deterministic but len(next_states) = 0, then automaton is incomplete, return None. if self.is_deterministic() and len(next_states) > 0: return next_states[0] if not self.is_deterministic(): return next_states
[docs] def init_state(self): """ Initial state of automaton. """ return int(self.spot_aut.get_init_state_number())
[docs] def final(self, state): """ Maps every state to its acceptance set. """ if not self.is_state_based_acc(): raise NotImplementedError return list(self.spot_aut.state_acc_sets(state).sets())
[docs] def acc_cond(self): """ Returns acceptance condition according to ggsolver definitions: See `ACC_REACH, ...` variables in Automaton class. See :meth:`SpotAutomaton.spot_acc_cond` for acceptance condition in spot's nomenclature. """ return self._acc_cond
[docs] def num_acc_sets(self): """ Number of acceptance sets. """ return self.spot_aut.num_sets()
[docs] def is_deterministic(self): """ Is the automaton deterministic? """ return bool(self.spot_aut.prop_universal() and self.spot_aut.is_existential())
[docs] def is_unambiguous(self): """ There is at most one run accepting a word (but it might be recognized several time). See """ return bool(self.spot_aut.prop_unambiguous())
[docs] def is_terminal(self): """ Automaton is weak, accepting SCCs are complete, accepting edges may not go to rejecting SCCs. An automaton is weak if the transitions of an SCC all belong to the same acceptance sets. See """ return bool(self.spot_aut.prop_terminal())
[docs] def is_stutter_invariant(self): """ The property recognized by the automaton is stutter-invariant (see """ return bool(self.spot_aut.prop_stutter_invariant())
[docs] def is_complete(self): """ Is the automaton complete? """ return bool(spot.is_complete(self.spot_aut))
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def is_semi_deterministic(self): """ Is the automaton semi-deterministic? See """ return bool(spot.is_semi_deterministic(self.spot_aut))
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def acc_name(self): """ Name of acceptance condition as per spot's nomenclature. """ return self.spot_aut.acc().name()
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def spot_acc_cond(self): """ Acceptance condition in spot's nomenclature. """ return str(self.spot_aut.get_acceptance())
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def formula(self): """ The LTL Formula. """ return self._formula
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def is_state_based_acc(self): """ Is the acceptance condition state-based? """ return bool(self.spot_aut.prop_state_acc())
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def is_weak(self): """ Are transitions of an SCC all belong to the same acceptance sets? """ return bool(self.spot_aut.prop_weak())
[docs] @models.register_property(Automaton.GRAPH_PROPERTY) def is_inherently_weak(self): """ Is it the case that accepting and rejecting cycles cannot be mixed in the same SCC? """ return bool(self.spot_aut.prop_inherently_weak())
def sat2formula(atoms, sat_assignments): """ Given a subset of elements from powerset(atoms), generates a propositional logic formula that accepts exactly those elements. :param atoms: (Iterable[str]) The set of atoms. :param sat_assignments: (Iterable[powerset(atoms)]) A subset of powerset(atoms) representing satisfiable assignments of the formula to be generated. :return: (str) String representing PL formula that accepts exactly the satisfying assignments. """ # Generate all clauses formula = [] for assignment in sat_assignments: # Each clause includes an ANDing of atoms in assignment and ANDing of negation of atoms not in assignment complete_acc = [p if p in assignment else f"!{p}" for p in atoms] formula.append(f"({' & '.join(complete_acc)})") # Construct DNF formula by joining all clauses using disjunction formula = " | ".join(formula) formula = PL(f_str=formula, atoms=atoms).simplify() # Simplify the formula return PL(f_str=formula, atoms=atoms)