Comparing each, Hash[] and inject performance

each_hash_inject.rb

require 'benchmark'

runs = 1000

original_data = {}
1000.times do |t| # 1000 depts with 100 guys each
  original_data["dept_#{t}"] = (1..100).to_a
end

def employee_name(id)
  id.to_s
end

Benchmark.bm do|b|
  b.report("each") do
    runs.times do
      new_data = {}
      original_data.each { |dept, employee_ids| new_data[dept] = employee_ids.collect{ |id| employee_name(id) } }
    end
  end

  b.report("Hash[]") do
    runs.times do
      new_data = Hash[ original_data.collect{ |dept, employee_ids| [dept, employee_ids.collect{ |id| employee_name(id) }] } ]  
    end
  end

  b.report("inject") do
    runs.times do
      new_data = original_data.inject({}) { |new_hash, dept_and_ids| new_hash[dept_and_ids[0]] = dept_and_ids[1].collect{ |id| employee_name(id) }; new_hash; }
    end
  end
end