Ruby string formatting performance

ruby_string_perf.rb

require "benchmark/ips"

def with_interpolation(a = "a", b = "b")
  "#{a}--#{b}"
end

def with_cryptic_percentage(a = "a", b = "b")
  "%s--%s" % [a,b]
end

def with_kernel_format(a = "a", b = "b")
  format("%s--%s", a,b)
end

Benchmark.ips do |x|
  x.report("with_interpolation") { with_interpolation }
  x.report("with_cryptic_percentage") { with_cryptic_percentage } 
  x.report("with_kernel_format") { with_kernel_format }

  x.compare!
end

__END__

Calculating -------------------------------------
  with_interpolation    62.236k i/100ms
with_cryptic_percentage
                        41.634k i/100ms
  with_kernel_format    40.623k i/100ms
-------------------------------------------------
  with_interpolation      1.478M (± 8.9%) i/s -      7.344M
with_cryptic_percentage
                        721.723k (± 7.9%) i/s -      3.622M
  with_kernel_format    794.553k (± 8.0%) i/s -      3.981M

Comparison:
  with_interpolation:  1478331.6 i/s
  with_kernel_format:   794552.8 i/s - 1.86x slower
with_cryptic_percentage:   721723.3 i/s - 2.05x slower