# File lib/algorithms/simulated_annealing.rb, line 33
    def initialize ( opts )
      @support = opts[:support]
      @global_threshold = opts[:global_threshold] ||
         opts[:global_thresold] # :) backward compatibility
      @step_multiplicator = opts[:step_multiplicator]
      @temperature = opts[:initial_temperature]
      @cur_cost = opts[:initial_cost]
      @output = opts[:output] || STDOUT
      @iteration_modulus = opts[:iteration_modulus] || 1
      @step_modulus = opts[:step_modulus] || 1
      @generator = opts[:generator]
      @iteration_max = opts[:iteration_max] || (1.0 / 0.0) # Infinity
      @progression = ' '
      @diff_cost = 0
      @iteration = 0
      @probability_threshold = 0
      @argmin = @support.copy_of_the_current_solution
      @min = @cur_cost
    end

# File lib/algorithms/simulated_annealing.rb, line 138
    def choose_probability ( generator=nil )
      1.0.choose(generator)
    end

# File lib/algorithms/simulated_annealing.rb, line 111
    def disp ( output=@output )
      args = [ @up, @same, @down, @reject, @temperature,
               @proba_mean / @proba_mean_count,
               @threshold_mean / @threshold_mean_count, @cur_cost ]
      fmt = '- { "+%-5d|=%-5d|-%-5d|x%-5d", temp: %-4f, ' +
                'prob: %-7f, thres: %-7f, cost: %-5s }'
      output.puts fmt % args
      reset
    end

# File lib/algorithms/simulated_annealing.rb, line 132
    def progression ( x )
      @progression = x
      disp if (@iteration % @iteration_modulus).zero?
    end

# File lib/algorithms/simulated_annealing.rb, line 55
    def reset
      @up, @down, @same, @reject, @proba_mean, @proba_mean_count,
      @threshold_mean, @threshold_mean_count = @@zeros
    end

# File lib/algorithms/simulated_annealing.rb, line 61
    def run
      reset
      @output.puts '---'
      while @cur_cost > @global_threshold and @iteration < @iteration_max
        # puts "Iteration(#{it}) #{@cur_cost}"
        @transition = @support.choose_transition(@generator)
        @diff_cost = @support.transition_cost(@cur_cost, @transition)

        @iteration += 1
        if (@iteration % @step_modulus).zero?
          @temperature *= @step_multiplicator
        end

        if @diff_cost > 0
          @probability_threshold = Math.exp(- @diff_cost.to_f / @temperature)
          @proba = choose_probability(@generator)
          @proba_mean += @proba
          @proba_mean_count += 1
          @threshold_mean += @probability_threshold
          @threshold_mean_count += 1
          if @proba < @probability_threshold
            progression '+'
            @up += 1
          else
            progression ' '
            @reject += 1
            next
          end
        else
          @probability_threshold = 1
          @proba = 1
          if @diff_cost.zero?
            @same += 1
            progression '='
          else
            @down += 1
            progression '-'
          end
        end

        @support.apply_transition(@transition)
        @cur_cost += @diff_cost
        if @cur_cost < @min
          @min = @cur_cost
          @argmin = @support.copy_of_the_current_solution
        end
      end
    end

# File lib/algorithms/simulated_annealing.rb, line 122
    def summary
      @output.puts %Q[
        |---
        |Found a mininum: #@cur_cost
        |Temperature at the end: #@temperature
        |Nb iterations: #@iteration
      ].head_cut!
    end