下面的代码在 Ruby 1.8/1.9 上通过了测试，但是当我在 Ruby 1.9.2 上运行这些测试时，我没有收到Array#sum. 例如，
NoMethodError: undefined method `sum' for [3.2, 3.0, 1.5, 0.73, 0.47, 0.23]:Array
我遇到了inject(:+)，但是当我尝试将其替换为 where sumis 时，它又产生了其他问题。有两种sum使用方法，time_required和balance_queues. 在第二种方法中，将其用于旧代码很复杂q1.sum - q2.sum。尽可能多的细节/解释会有所帮助。
class FairDistribution
def initialize(jobs, num_of_queues)
@queues = [ jobs.sort.reverse ]
(num_of_queues - 1).times { @queues << [] }
# Balance the queues until they are perfectly balanced
while !balance_all_queues do; end
end
# Time required for all queues processing
def time_required
@queues.map { |q| q.sum }.max #SUM
end
# The actual distribution of jobs across the queues
def distribution
@queues
end
private
# Runs through all queues and balances them against each other.
# Makes one pass only and returns FALSE if there was nothing changed
# during the pass.
def balance_all_queues
updated = false
@queues.each_with_index do |q1, qi1|
(qi1+1 ... @queues.size).each do |qi2|
res = balance_queues(q1, @queues[qi2])
updated ||= res
end
end
return !updated
end
# Balances the two queues between themselves by finding the best possible
# swap of jobs between them. If there's nothing to be improved, returns FALSE.
def balance_queues(q1, q2)
delta = q1.sum - q2.sum #SUM
return false if delta == 0
best_swap = nil
best_swap_delta = delta.abs
q1.each_combination do |c1|
best_swap, best_swap_delta = choose_better_swap(c1, [], delta, best_swap, best_swap_delta)
q2.each_combination do |c2|
best_swap, best_swap_delta = choose_better_swap(c1, c2, delta, best_swap, best_swap_delta)
end
end
best_swap.apply(q1, q2) unless best_swap.nil?
return !best_swap.nil?
end
# Sees if the swap we have at hand is better than our current best
# swap and replaces the latest if it is.
def choose_better_swap(c1, c2, delta, best_swap, best_swap_delta)
unless c1 == c2
s = Swap.new(c1, c2, delta)
best_swap, best_swap_delta = s, s.delta if s.delta < best_swap_delta
end
return best_swap, best_swap_delta
end
end