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sort_by_v_shuffle.rb
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sort_by_v_shuffle.rb
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require "benchmark"
# This benchmark demonstrates the speed of Array#shuffle versus sorting by
# random numbers. This is in reference to ordering examples using the
# --order=rand command line flag. Array#shuffle also respects seeded random via
# Kernel.srand.
LIST = (1..1_000).to_a.freeze
Benchmark.bmbm do |x|
x.report("sort_by") do
1_000.times do
LIST.sort_by { Kernel.rand(LIST.size) }
end
end
x.report("shuffle") do
1_000.times do
LIST.shuffle
end
end
# http://en.wikipedia.org/wiki/Fisher-Yates_shuffle
#
# We use this algorithm as an alternative to `shuffle` on
# rubies (< 1.9.3) for which Array#shuffle does not accept
# a `:random` option. We do this to avoid affecting ruby's
# global randomization.
x.report('fisher-yates') do
1_000.times do
rng = Random.new
list = LIST.dup
LIST.size.times do |i|
j = i + rng.rand(LIST.size - i)
next if i == j
list[i], list[j] = list[j], list[i]
end
end
end
end
=begin
Ruby 2.0.0:
Rehearsal ------------------------------------------------
sort_by 0.570000 0.010000 0.580000 ( 0.581875)
shuffle 0.020000 0.000000 0.020000 ( 0.021524)
fisher-yates 0.370000 0.020000 0.390000 ( 0.387855)
--------------------------------------- total: 0.990000sec
user system total real
sort_by 0.560000 0.000000 0.560000 ( 0.561014)
shuffle 0.010000 0.000000 0.010000 ( 0.019814)
fisher-yates 0.350000 0.010000 0.360000 ( 0.358932)
Ruby 1.9.3:
Rehearsal ------------------------------------------------
sort_by 0.690000 0.010000 0.700000 ( 0.701035)
shuffle 0.020000 0.000000 0.020000 ( 0.017603)
fisher-yates 0.440000 0.020000 0.460000 ( 0.464778)
--------------------------------------- total: 1.180000sec
user system total real
sort_by 0.690000 0.000000 0.690000 ( 0.697824)
shuffle 0.020000 0.000000 0.020000 ( 0.018622)
fisher-yates 0.440000 0.010000 0.450000 ( 0.452260)
JRuby:
Rehearsal ------------------------------------------------
sort_by 2.550000 0.050000 2.600000 ( 1.325000)
shuffle 0.090000 0.000000 0.090000 ( 0.057000)
fisher-yates 0.770000 0.010000 0.780000 ( 0.477000)
--------------------------------------- total: 3.470000sec
user system total real
sort_by 0.470000 0.010000 0.480000 ( 0.442000)
shuffle 0.040000 0.000000 0.040000 ( 0.042000)
fisher-yates 0.300000 0.010000 0.310000 ( 0.283000)
=end