bench_file.rb

require 'benchmark/ips'
require "tempfile"

def Warning.warn(*); end

data = Tempfile.new

100_000.times { |i| data.write "#{i} #{[*?a..?z].sample(7).join}\n" }

Benchmark.ips do |x|
  x.report("lines")       { data.lines.map{ |line| line.split }.map{ |pid, prog| [pid.to_i, prog] } }
  x.report("each_slice")  { data.to_s.split.each_slice(2).map { |pid, prog| [pid.to_i, prog] } }
  x.report("with_object") { data.to_s.split.each_slice(2).with_object([]) { |(pid, prog), container| container << [pid.to_i, prog] } }
  x.report("each_line")   { data.each_line.map { |line| line.split.yield_self {|pid, prog| [pid.to_i, prog] } } }
  x.compare!
end

data.close
data.unlink

__END__

Warming up --------------------------------------
               lines    11.178k i/100ms
          each_slice    13.943k i/100ms
         with_object    17.839k i/100ms
           each_line    22.733k i/100ms
Calculating -------------------------------------
               lines    140.668k (±12.9%) i/s -    693.036k in   5.041439s
          each_slice    192.749k (± 7.5%) i/s -    962.067k in   5.022303s
         with_object    182.791k (±17.8%) i/s -    874.111k in   5.024672s
           each_line    239.246k (±16.3%) i/s -      1.159M in   5.087971s

Comparison:
           each_line:   239245.5 i/s
          each_slice:   192749.2 i/s - same-ish: difference falls within error
         with_object:   182791.0 i/s - same-ish: difference falls within error
               lines:   140667.7 i/s - 1.70x  slower