Class: Lernen::Algorithm::KearnsVaziraniVPA::DiscriminationTreeVPA

Inherits:
Object
  • Object
show all
Defined in:
lib/lernen/algorithm/kearns_vazirani_vpa/discrimination_tree_vpa.rb

Overview

DiscriminationTreeVPA is a extended version of discrimination tree for VPA.

Constant Summary collapse

Node = 
Data.define(:access, :suffix, :branch)
Leaf = 
Data.define(:prefix)

Instance Method Summary collapse

Constructor Details

#initialize(alphabet, call_alphabet, return_alphabet, sul, cex:, cex_processing:) ⇒ DiscriminationTreeVPA

: (

  Array[In] alphabet,
  Array[Call] call_alphabet,
  Array[Return] return_alphabet,
  System::MooreLikeSUL[In | Call | Return, bool] sul,
  cex: Array[In],
  cex_processing: cex_processing_method
) -> void



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# File 'lib/lernen/algorithm/kearns_vazirani_vpa/discrimination_tree_vpa.rb', line 56

def initialize(alphabet, call_alphabet, return_alphabet, sul, cex:, cex_processing:)
  @alphabet = alphabet
  @call_alphabet = call_alphabet
  @return_alphabet = return_alphabet
  @sul = sul
  @cex_processing = cex_processing

  @path_hash = {}

  @root = Node[[], [], {}]

  empty_out = sul.query_empty
  @root.branch[empty_out] = Leaf[[]]
  @path_hash[[]] = [empty_out]

  cex_out = sul.query_last(cex)
  @root.branch[cex_out] = Leaf[cex] # steep:ignore
  @path_hash[cex] = [cex_out] # steep:ignore
end

Instance Method Details

#build_hypothesis ⇒ Object

Constructs a hypothesis automaton from this discrimination tree.

: () -> [Automaton::VPA[In, Call, Return], Hash[Integer, Array[In | Call | Return]]]



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# File 'lib/lernen/algorithm/kearns_vazirani_vpa/discrimination_tree_vpa.rb', line 79

def build_hypothesis
  transition_function = {}
  return_transition_function = {}

  queue = []
  prefix_to_state = {}
  state_to_prefix = {}

  queue << []
  prefix_to_state[[]] = prefix_to_state.size
  state_to_prefix[state_to_prefix.size] = []

  until queue.empty?
    prefix = queue.shift
    state = prefix_to_state[prefix]
    @alphabet.each do |input|
      word = prefix + [input]
      next_prefix = sift(word)

      unless prefix_to_state.include?(next_prefix)
        queue << next_prefix
        prefix_to_state[next_prefix] = prefix_to_state.size
        state_to_prefix[state_to_prefix.size] = next_prefix
      end

      next_state = prefix_to_state[next_prefix]
      transition_function[[state, input]] = next_state

      found_states = prefix_to_state.values

      return_transition_function.each do |(return_state, return_input), return_transition_guard|
        return_prefix = state_to_prefix[return_state]
        @call_alphabet.each do |call_input|
          word = prefix + [call_input] + return_prefix + [return_input]
          next_prefix = sift(word)

          unless prefix_to_state.include?(next_prefix)
            queue << next_prefix
            prefix_to_state[next_prefix] = prefix_to_state.size
            state_to_prefix[state_to_prefix.size] = next_prefix
          end

          next_state = prefix_to_state[next_prefix]
          return_transition_guard[[state, call_input]] = next_state
        end
      end

      @return_alphabet.each do |return_input|
        return_transition_guard = return_transition_function[[state, return_input]] = {}
        found_states.each do |call_state|
          call_prefix = state_to_prefix[call_state]
          @call_alphabet.each do |call_input|
            word = call_prefix + [call_input] + prefix + [return_input]
            next_prefix = sift(word)

            unless prefix_to_state.include?(next_prefix)
              queue << next_prefix
              prefix_to_state[next_prefix] = prefix_to_state.size
              state_to_prefix[state_to_prefix.size] = next_prefix
            end

            next_state = prefix_to_state[next_prefix]
            return_transition_guard[[call_state, call_input]] = next_state
          end
        end
      end
    end
  end

  accept_state_set =
    state_to_prefix.to_a.filter { |(_, prefix)| @path_hash[prefix][0] }.to_set { |(state, _)| state }
  automaton = Automaton::VPA.new(0, accept_state_set, transition_function, return_transition_function)

  [automaton, state_to_prefix]
end

#refine_hypothesis(cex, hypothesis, state_to_prefix) ⇒ Object

Update this classification tree by the given ‘cex`.

: (

  Array[In | Call | Return] cex,
  Automaton::VPA[In, Call, Return] hypothesis,
  Hash[Integer, Array[In | Call | Return]] state_to_prefix
) -> void



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# File 'lib/lernen/algorithm/kearns_vazirani_vpa/discrimination_tree_vpa.rb', line 162

def refine_hypothesis(cex, hypothesis, state_to_prefix)
  conf_to_prefix = ->(conf) do
    prefix = []

    conf.stack.each do |state, call_input|
      prefix.concat(state_to_prefix[state])
      prefix << call_input
    end
    prefix.concat(state_to_prefix[conf.state])

    prefix
  end

  acex = CexProcessor::PrefixTransformerAcex.new(cex, @sul, hypothesis, conf_to_prefix)
  n = CexProcessor.process(acex, cex_processing: @cex_processing)
  old_prefix = cex[0...n]
  new_input = cex[n]
  new_suffix = cex[n + 1...]

  _, old_conf = hypothesis.run(old_prefix) # steep:ignore
  _, replace_conf = hypothesis.step(old_conf, new_input)

  new_access_conf = Automaton::VPA::Conf[hypothesis.initial_state, replace_conf.stack] # steep:ignore
  new_access = conf_to_prefix.call(new_access_conf)

  old_state_prefix = state_to_prefix[old_conf.state] # steep:ignore
  if @alphabet.include?(new_input) # steep:ignore
    new_prefix = old_state_prefix + [new_input]
  else
    call_state, call_input = old_conf.stack.last # steep:ignore
    call_prefix = state_to_prefix[call_state]
    new_prefix = call_prefix + [call_input] + old_state_prefix + [new_input]
  end
  new_out = @sul.query_last(new_access + new_prefix + new_suffix) # steep:ignore

  replace_prefix = state_to_prefix[replace_conf.state] # steep:ignore
  replace_out = @sul.query_last(new_access + replace_prefix + new_suffix) # steep:ignore

  replace_node_path = @path_hash[replace_prefix]
  replace_node_parent = @root
  replace_node = @root.branch[replace_node_path.first] # steep:ignore
  replace_node_path[1..].each do |out| # steep:ignore
    replace_node_parent = replace_node
    replace_node = replace_node.branch[out] # steep:ignore
  end

  new_node = Node[new_access, new_suffix, {}] # steep:ignore
  replace_node_parent.branch[replace_node_path.last] = new_node # steep:ignore

  new_node.branch[new_out] = Leaf[new_prefix] # steep:ignore
  @path_hash[new_prefix] = replace_node_path + [new_out]

  new_node.branch[replace_out] = Leaf[replace_prefix] # steep:ignore
  @path_hash[replace_prefix] = replace_node_path + [replace_out]
end