loop_vs_while.rb

def by_loop
  loop do
    break if yield
  end
end

def by_while
  while true
    break if yield
  end
end

require 'benchmark'
x = 10_000_000

Benchmark.bmbm(20) do |b|
  b.report('loop:  '){ n = 0; by_loop{ (n += 1) == x }}
  b.report('while: '){ n = 0; by_while{ (n += 1) == x }}
end

results.txt

ruby 1.8.7 (2008-08-11 patchlevel 72) [x86_64-linux]
Rehearsal -------------------------------------------------------
loop:                20.310000   0.120000  20.430000 ( 20.441405)
while:               14.490000   0.030000  14.520000 ( 14.524623)
--------------------------------------------- total: 34.950000sec

                          user     system      total        real
loop:                20.490000   0.110000  20.600000 ( 20.607152)
while:               15.020000   0.040000  15.060000 ( 15.054473)

ruby 1.9.2dev (2009-02-05 trunk 22073) [x86_64-linux]
Rehearsal -------------------------------------------------------
loop:                 4.680000   0.000000   4.680000 (  4.681246)
while:                2.830000   0.000000   2.830000 (  2.826771)
---------------------------------------------- total: 7.510000sec

                          user     system      total        real
loop:                 4.660000   0.000000   4.660000 (  4.660789)
while:                2.810000   0.010000   2.820000 (  2.816847)