Performance test script

perf.rb

list = [
  { :path => 'path_C', :name => 'vm_x' },
  { :path => 'path_a', :name => 'vm_y' },
  { :path => 'path_b', :name => 'vm_z' },
  { :path => 'path_d', :name => 'vm_b' },
  { :path => 'path_D', :name => 'vm_a' },
]

def build_output_michal(list)
  result_map = {}
  list.each do |vm|
    full_path = "#{vm[:path]}/#{vm[:name]}"
    result_map[full_path] = "#{full_path}\n" <<
      "  powerstate: #{vm[:power_state]}\n" <<
      "  name:       #{vm[:name]}\n" <<
      "  hostname:   #{vm[:hostname] || '--------'}\n" <<
      "  instanceid: #{vm[:instance_uuid]}\n" <<
      "  ipaddress:  #{vm[:ipaddress] || '---.---.---.---'}\n" <<
      "  template:   #{vm[:is_a_template]}\n"
  end
  result_map.keys.sort { |l, r| l.downcase <=> r.downcase }.map { |k| result_map[k] }.join("\n")
end

def build_output_michal_optimized(list)
  result_map = {}
  list.each do |vm|
    result_map["#{vm[:path]}/#{vm[:name]}"] = vm
  end
  memo = ''
  result_map.keys.sort { |l, r| l.downcase <=> r.downcase }.each do |full_path|
    vm = result_map[full_path]

    # Add a blank line if this isn't the first record
    memo << "\n" unless memo.empty?

    # Store the next record string and return the memo value
    memo << full_path << "\n" <<
      "  powerstate: #{vm[:power_state]}\n" <<
      "  name:       #{vm[:name]}\n" <<
      "  hostname:   #{vm[:hostname] || '--------'}\n" <<
      "  instanceid: #{vm[:instance_uuid]}\n" <<
      "  ipaddress:  #{vm[:ipaddress] || '---.---.---.---'}\n" <<
      "  template:   #{vm[:is_a_template]}\n"
  end
  memo
end

def build_output_michal_new(list)
  list = list.map do |vm|
    full_path = "#{vm[:path]}/#{vm[:name]}"
    {
      :full_path => full_path,
      :sort_key => full_path.downcase,
      :vm => vm,
    }
  end

  memo = ''
  list.sort { |l, r| l[:sort_key] <=> r[:sort_key] }.each do |m|
    vm = m[:vm]

    # Add a blank line if this isn't the first record
    memo << "\n" unless memo.empty?

    # Store the next record string and return the memo value
    memo <<
      "#{m[:full_path]}\n" <<
      "  powerstate: #{vm[:power_state]}\n" <<
      "  name:       #{vm[:name]}\n" <<
      "  hostname:   #{vm[:hostname] || '--------'}\n" <<
      "  instanceid: #{vm[:instance_uuid]}\n" <<
      "  ipaddress:  #{vm[:ipaddress] || '---.---.---.---'}\n" <<
      "  template:   #{vm[:is_a_template]}\n"
  end
  memo
end

def build_output_jill(list)
  list.sort { |l, r|

    # Sort by the full path + name in alphabetical order
    "#{l[:path]}/#{l[:name]}".downcase <=> "#{r[:path]}/#{r[:name]}".downcase
  }.inject(String.new) { |memo, vm|

    # Add a blank line if this isn't the first record
    memo << "\n" if memo == ""

    # Store the next record string and return the memo value
    memo <<
      "#{vm[:path]}/#{vm[:name]}\n" <<
      "  powerstate: #{vm[:power_state]}\n" <<
      "  name:       #{vm[:name]}\n" <<
      "  hostname:   #{vm[:hostname] || '--------'}\n" <<
      "  instanceid: #{vm[:instance_uuid]}\n" <<
      "  ipaddress:  #{vm[:ipaddress] || '---.---.---.---'}\n" <<
      "  template:   #{vm[:is_a_template]}\n"
  }
end

test_proc = method("build_output_#{ARGV[0]}".to_sym)

puts test_proc.call(list)

for i in 1 .. 1000000
  test_proc.call(list)
end

use the script like this:
ruby perf.rb michal_optimized
ruby perf.rb jill
etc.