RANGE = (0..1000)
array = RANGE.to_a
hash = RANGE.inject({}) { |h,i| h[i] = true; h }
def test_member?(data)
  RANGE.each { |i| data.member? i }
end
require 'benchmark'
Benchmark.bm(5) do |timer|
  timer.report('Array') { test_member?(array) }
  timer.report('Hash') { test_member?(hash) }
end

user     system      total        real
Array  0.260000   0.060000   0.320000 (  0.332583)
Hash   0.010000   0.000000   0.010000 (  0.001242)

user     system      total        real
Array  0.280000   0.050000   0.330000 (  0.318784)
Hash   0.000000   0.000000   0.000000 (  0.001216)

Benchmark.bm(5) do |timer|
  timer.report('Array') { 1000.times { RANGE.each { |i| array[i] } } }
  timer.report('Hash') { 1000.times { RANGE.each { |i| hash[i] } } }
end

user     system      total        real
Array  0.950000   0.210000   1.160000 (  1.175042)
Hash   1.010000   0.210000   1.220000 (  1.221090)

user     system      total        real
Array  1.000000   0.180000   1.180000 (  1.220659)
Hash   1.060000   0.170000   1.230000 (  1.252879)

def write_to_file
  File.open('out', 'w') { |f| f.write('a') }
end
puts Benchmark.measure { 10000.times { write_to_file } }

0.120000   0.360000   0.480000 (  0.500653)

0.130000   0.360000   0.490000 (  0.499884)