Class: ActiveFacts::DependencyAnalyser

Inherits:
Object
  • Object
show all
Defined in:
lib/activefacts/dependency_analyser.rb

Instance Method Summary collapse

Constructor Details

#initialize(enumerable, &block) ⇒ DependencyAnalyser

Returns a new instance of DependencyAnalyser.



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# File 'lib/activefacts/dependency_analyser.rb', line 3

def initialize enumerable, &block
  @enumerable = enumerable
  analyse_precursors &block
end

Instance Method Details

#analyse_chasers ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 40

def analyse_chasers
  analyse_precursors_transitive unless @precursors_transitive
  analyse_followers unless @followers

  # A follower is an object with us as a precursor, that has no new precursors of its own
  @chasers = {}
  @enumerable.each do |item|
	@chasers[item] =
	  @enumerable.select do |follower|
 @precursors[follower].include?(item) and
 (@precursors_transitive[follower] - @precursors_transitive[item] - [item]).size == 0
	  end
  end
end

#analyse_followers ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 31

def analyse_followers
  @followers = Hash.new{|h, k| h[k] = [] }
  @enumerable.each do |item|
	@precursors[item].each do |precursor|
	  @followers[precursor] << item
	end
  end
end

#analyse_precursors(&block) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 8

def analyse_precursors &block
  @precursors = {}
  @enumerable.each do |item|
	@precursors[item] = block.call(item)
  end
end

#analyse_precursors_transitive ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 15

def analyse_precursors_transitive
  all_precursors = proc do |item|
	  p = @precursors[item]
	  all =
 p + p.map do |precursor|
   p.include?(precursor) ? [] : all_precursors.call(precursor)
 end.flatten
	  all.uniq
	end

  @precursors_transitive = {}
  @enumerable.each do |item|
	@precursors_transitive[item] = all_precursors.call(item)
  end
end

#chasers(item, &b) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 135

def chasers item, &b
  analyse_chasers unless @chasers
  if item
	if block_given?
	  Array(@chasers[item]).each { |follower| yield follower, item }
	else
	  Array(@chasers[item])
	end
  else
	@enumerable.each do |item|
	  follower(item, &b)
	end
  end
end

#each(&b) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 82

def each &b
  if block_given?
	@enumerable.each { |item| yield item}
  else
	@enumerable
  end
end

#followers(item = nil, &b) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 120

def followers item = nil, &b
  analyse_followers unless @followers
  if item
	if block_given?
	  Array(@followers[item]).each { |follower| yield follower, item }
	else
	  Array(@followers[item])
	end
  else
	@enumerable.each do |item|
	  followers(item, &b)
	end
  end
end

#page_rank(damping = 0.85, &weight) ⇒ Object

Compute the page rank of the objects If used, the block shold return the starting weight



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# File 'lib/activefacts/dependency_analyser.rb', line 152

def page_rank damping = 0.85, &weight
  weight ||= proc {|item| 1.0}

  @total = 0
  @rank = {}
  @enumerable.each do |item|
	@total += 
	  (@rank[item] = weight.call(item) * 1.0)
  end
  # Normalize:
  @enumerable.each do |item|
	@rank[item] /= @total
  end

  50.times do |iteration|
	@enumerable.each do |item|
	  links = (precursors(item) + followers(item)).uniq
	  linked_rank = links.map do |l|
   onward_links = (precursors(l) + followers(l)).uniq || @enumerable.size
   @rank[l] / onward_links.size
 end.inject(&:+) || 0
	  @rank[item] = (1.0-damping) + damping*linked_rank
	end
  end

  @rank
end

#precursors(item = nil, &b) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 90

def precursors item = nil, &b
  analyse_precursors unless @precursors
  if item
	if block_given?
	  Array(@precursors[item]).each { |precursor| yield precursor, item }
	else
	  Array(@precursors[item])
	end
  else
	@enumerable.each do |item|
	  precursors(item, &b)
	end
  end
end

#precursors_transitive(item, &b) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 105

def precursors_transitive item, &b
  analyse_precursors_transitive unless @precursors_transitive
  if item
	if block_given?
	  Array(@precursors_transitive[item]).each { |precursor| yield precursor, item }
	else
	  Array(@precursors_transitive[item])
	end
  else
	@enumerable.each do |item|
	  precursors_transitive(item, &b)
	end
  end
end

#tsort(&block) ⇒ Object 



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# File 'lib/activefacts/dependency_analyser.rb', line 55

def tsort &block
  analyse_precursors unless @precursors
  emitted = {}
  pass = 0
  until emitted.size == @enumerable.size
	next_items = []
	blocked =
	  @enumerable.inject({}) do |hash, item|
 next hash if emitted[item]
 blockers = item.precursors.select{|precursor| !emitted[precursor]}
 if blockers.size > 0
   hash[item] = blockers
 else
   next_items << item
 end
 hash
	  end
	return blocked if next_items.size == 0	# Cannot make progress
	# puts "PASS #{pass += 1}"
	next_items.each do |item|
	  block.call(item)
	  emitted[item] = true
	end
  end
  nil
end