aalpy.automata.Mdp
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import random from collections import defaultdict from aalpy.base import Automaton, AutomatonState class MdpState(AutomatonState): def __init__(self, state_id, output=None): super().__init__(state_id) self.output = output # each child is a tuple (Node(output), probability) self.transitions = defaultdict(list) class Mdp(Automaton): """Markov Decision Process.""" def __init__(self, initial_state: MdpState, states: list): super().__init__(initial_state, states) def reset_to_initial(self): self.current_state = self.initial_state def step(self, letter): """Next step is determined based on transition probabilities of the current state. Args: letter: input Returns: output of the current state """ if letter is None: return self.current_state.output prob = random.random() probability_distributions = [i[1] for i in self.current_state.transitions[letter]] states = [i[0] for i in self.current_state.transitions[letter]] new_state = random.choices(states, probability_distributions, k=1)[0] self.current_state = new_state return self.current_state.output def step_to(self, inp, out): """Performs a step on the automaton based on the input `inp` and output `out`. Args: inp: input out: output Returns: output of the reached state, None otherwise """ for new_state in self.current_state.transitions[inp]: if new_state[0].output == out: self.current_state = new_state[0] return out return None
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class MdpState(AutomatonState): def __init__(self, state_id, output=None): super().__init__(state_id) self.output = output # each child is a tuple (Node(output), probability) self.transitions = defaultdict(list)
Helper class that provides a standard way to create an ABC using inheritance.
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def __init__(self, state_id, output=None): super().__init__(state_id) self.output = output # each child is a tuple (Node(output), probability) self.transitions = defaultdict(list)
Single state of an automaton. Each state consists of a state id, a dictionary of transitions, where the keys are inputs and the values are the corresponding target states, and a prefix that leads to the state from the initial state.
Args:
state_id(Any): used for graphical representation of the state. A good practice is to keep it unique.
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class Mdp(Automaton): """Markov Decision Process.""" def __init__(self, initial_state: MdpState, states: list): super().__init__(initial_state, states) def reset_to_initial(self): self.current_state = self.initial_state def step(self, letter): """Next step is determined based on transition probabilities of the current state. Args: letter: input Returns: output of the current state """ if letter is None: return self.current_state.output prob = random.random() probability_distributions = [i[1] for i in self.current_state.transitions[letter]] states = [i[0] for i in self.current_state.transitions[letter]] new_state = random.choices(states, probability_distributions, k=1)[0] self.current_state = new_state return self.current_state.output def step_to(self, inp, out): """Performs a step on the automaton based on the input `inp` and output `out`. Args: inp: input out: output Returns: output of the reached state, None otherwise """ for new_state in self.current_state.transitions[inp]: if new_state[0].output == out: self.current_state = new_state[0] return out return None
Markov Decision Process.
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def __init__(self, initial_state: MdpState, states: list): super().__init__(initial_state, states)
Args:
initial_state (AutomatonState): initial state of the automaton
states (list) : list containing all states of the automaton
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def reset_to_initial(self): self.current_state = self.initial_state
Resets the current state of the automaton to the initial state
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def step(self, letter): """Next step is determined based on transition probabilities of the current state. Args: letter: input Returns: output of the current state """ if letter is None: return self.current_state.output prob = random.random() probability_distributions = [i[1] for i in self.current_state.transitions[letter]] states = [i[0] for i in self.current_state.transitions[letter]] new_state = random.choices(states, probability_distributions, k=1)[0] self.current_state = new_state return self.current_state.output
Next step is determined based on transition probabilities of the current state.
Args:
letter: input
Returns:
output of the current state
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def step_to(self, inp, out): """Performs a step on the automaton based on the input `inp` and output `out`. Args: inp: input out: output Returns: output of the reached state, None otherwise """ for new_state in self.current_state.transitions[inp]: if new_state[0].output == out: self.current_state = new_state[0] return out return None
Performs a step on the automaton based on the input inp
and output out
.
Args:
inp: input
out: output
Returns:
output of the reached state, None otherwise