Comparing [].join to string interpolation, different ruby versions

benchmark.rb

require 'benchmark'

n = 1_000_000

def key_arr(prefix, id, *suffixes)
  [prefix, id, suffixes].flatten.compact.join ":"
end

def key_str1(prefix, id, *suffixes)
  "#{prefix}:#{id}:#{suffixes.flatten.compact.join(':')}"
end

def key_str2(prefix, id, *suffixes)
  s = suffixes.flatten.compact.join(':')
  "#{prefix}:#{id}:#{s}"
end

def key_str3(prefix, id, *suffixes)
  s = suffixes.join(':')
  "#{prefix}:#{id}:#{s}"
end

pre = 'scenario'
id = 100
suff = ['class', 11231]

Benchmark.bm do |b|
  b.report("array") do
    n.times { key_arr(pre, id, suff) }
  end

  b.report("str1") do
    n.times { key_str1(pre, id, suff) }
  end

  b.report("str2") do
    n.times { key_str2(pre, id, suff) }
  end

  b.report("str3") do
    n.times { key_str3(pre, id, suff) }
  end
end

results.txt

# 1.9.2-p0
      user     system      total        real
array 3.540000   0.010000   3.550000 (  3.535814)
str1  3.380000   0.000000   3.380000 (  3.384282)
str2  3.410000   0.000000   3.410000 (  3.408285)
str3  2.620000   0.000000   2.620000 (  2.620290)

# 1.9.2-p290
      user     system      total        real
array 3.310000   0.000000   3.310000 (  3.307196)
str1  3.090000   0.000000   3.090000 (  3.096069)
str2  3.120000   0.010000   3.130000 (  3.119694)
str3  2.400000   0.000000   2.400000 (  2.399246)

# 1.9.3-p125 vanilla
       user     system      total        real
array 3.410000   0.000000   3.410000 (  3.413593)
str1  3.210000   0.000000   3.210000 (  3.213534)
str2  3.180000   0.000000   3.180000 (  3.187071)
str3  2.370000   0.000000   2.370000 (  2.365893)

# 1.9.3-p125 falcon patch (https://gist.github.com/1688857)
      user     system      total        real
array 3.350000   0.000000   3.350000 (  3.357074)
str1  3.020000   0.000000   3.020000 (  3.016996)
str2  3.090000   0.000000   3.090000 (  3.097042)
str3  2.320000   0.000000   2.320000 (  2.315476)

# Rubinius head (March 2012)
          user     system      total        real
array 11.266902   0.020766  11.287668 ( 10.898232)
str1   8.546355   0.004628   8.550983 (  8.443997)
str2   8.049362   0.001775   8.051137 (  8.014934)
str3   5.590899   0.002207   5.593106 (  5.569655)