enumerator_bench.rb

require 'benchmark'
require 'tsort'

def TSort.tsort_each_enum(each_node, each_child) # :yields: node
  return to_enum(__method__, each_node, each_child) unless block_given?

  TSort.each_strongly_connected_component(each_node, each_child) {|component|
    if component.size == 1
      yield component.first
    else
      raise Cyclic.new("topological sort failed: #{component.inspect}")
    end
  }
end

n = 1_000

g = {1=>[2, 3], 2=>[4], 3=>[2, 4], 4=>[]}
each_node = lambda {|&b| g.each_key(&b) }
each_child = lambda {|n, &b| g[n].each(&b) }

Benchmark.bmbm do |x|
  x.report('each array') {
    n.times do
      r = []
      TSort.tsort_each(each_node, each_child) {|n| r << n }
      r
    end
  }

  x.report('to_a') {
    n.times do
      TSort.tsort_each_enum(each_node, each_child).to_a
    end
  }
end

results.txt

~/t/ruby-perf ❯❯❯ ruby -v
ruby 2.1.3p242 (2014-09-19 revision 47630) [x86_64-darwin14.0]
~/t/ruby-perf ❯❯❯ ruby enum_tsort.rb
Rehearsal ----------------------------------------------
each array   0.780000   0.020000   0.800000 (  0.802514)
to_a         0.390000   0.020000   0.410000 (  0.408910)
------------------------------------- total: 1.210000sec

                 user     system      total        real
each array   0.820000   0.010000   0.830000 (  0.831467)
to_a         0.380000   0.010000   0.390000 (  0.393889)