Imperative code to investigate constraint satisfaction

lattice_enumerator.rb

@varnames = (0...9).collect {|i| "x#{i}".intern}

def manhattan_distance(p1,p2)
  (p1[0]-p2[0]).abs + (p1[1]-p2[1]).abs
end

def assignment_from_permutation(permutation,pos)
  h = Hash.new
  permutation.each_with_index do |i,idx|
    h[@varnames[i]] = pos[idx]
  end
  return h
end

def observed_distances(assignment)
  h = Hash.new
  assignment.keys.combination(2).each do |p1,p2|
    h[[p1,p2].sort] = manhattan_distance(assignment[p1],assignment[p2])
  end
  return h
end

def assignment_errors(assignment,target)
  observed = observed_distances(assignment)
  diff = Hash.new
  target.keys.each do |k|
    diff[k] = (observed[k] - target[k]).abs
  end
  return diff
end

def satisfy_constraints?(assignment,target)
  distances = observed_distances(assignment)
  target.keys.each do |k|
    return false if target[k] != distances[k]
  end
  return true
end

@positions = (0...3).to_a.repeated_permutation(2).to_a
@all_clues = observed_distances(
          assignment_from_permutation((0...9).to_a,@positions))

File.open("./many_counts.csv", "w+") do |f|
  f.sync = true
  1000.times do |trial|
    p trial
    cluefulness = rand(35) + 1
    some_clues = @all_clues.to_a.sample(cluefulness).to_h
    answers = 0
    (0...9).to_a.permutation(9).each_with_index do |perm,idx|
      assignment = assignment_from_permutation(perm,@positions)
      answers += 1 if satisfy_constraints?(assignment,some_clues)
    end
    f.write "#{cluefulness},#{answers},#{some_clues.inspect}\n"
    f.flush
  end
end