Module: Pione::PNML::OutputReduction

Defined in:
lib/pione/pnml/output-reduction.rb

Overview

OutputReduction is a net rewriting rule. This rule removes unnecessary output nodes of transitions. For example, the net likes the following

A --> empty place --> empty transition --> place -->  B

is rewritten as the following.

A -> place -> B

Class Method Summary collapse

Class Method Details

.find_subjects(net, env) ⇒ Array

Return subjects(source place, target transition, and the arc) if the net satisfies output reduction's condtions. The conditions are followings:

  • There is an empty source place. It is an output of named transition.
  • There is an empty target transition.
  • There is an arc that connects the source and the target.

Parameters:

Returns:

  • (Array) —

    source place, target transition, and the arc



26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
 
# File 'lib/pione/pnml/output-reduction.rb', line 26

def self.find_subjects(net, env)
  net.places.each do |place|
    # source place should be empty
    next unless Perspective.empty_place?(env, place)

    # source place should be an output of named transition
    next if net.find_all_transitions_by_target_id(place.id).map do |transition|
      not(Perspective.empty_transition?(env, transition))
    end.empty?

    transitions = net.find_all_transitions_by_source_id(place.id)

    # only one transition
    if transitions.size == 1
      transition = transitions.first

      # the transtion is connected to only one place at source side
      if net.find_all_places_by_target_id(transition.id).size == 1
        # target transition should be empty
        next unless Perspective.empty?(env, transition)

        return [place, transition, net.find_arc(place.id, transition.id)]
      end
    end
  end

  return nil
end

.rewrite(net, subjects, env) ⇒ void

This method returns an undefined value.

Rewrite the net with subjects by the following way.

  • Remove the subject place.
  • Remove the subject transition.
  • Remove the subject and related arcs.
  • Connect discontinuous nodes by new arcs.

Parameters:



69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
 
# File 'lib/pione/pnml/output-reduction.rb', line 69

def self.rewrite(net, subjects, env)
  place, transition, arc = subjects

  # remove subjects from the net
  net.places.delete(place)
  net.transitions.delete(transition)
  net.arcs.delete(arc)

  # remove related arcs
  input_arcs = net.find_all_arcs_by_target_id(place.id)
  input_arcs.each {|arc| net.arcs.delete(arc)}
  output_arcs = net.find_all_arcs_by_source_id(transition.id)
  output_arcs.each {|arc| net.arcs.delete(arc)}

  # append new arcs
  input_arcs.each do |input_arc|
    output_arcs.each do |output_arc|
      net.arcs << Arc.new(net, net.generate_id, input_arc.source_id, output_arc.target_id)
    end
  end
end