do-not-pass-kw-unless-needed.rb

require "benchmark/ips"

def foo(seq, kw)
end

def fast
  kw = { a: 1, b: 2, c: 3 }

  foo(1, kw)
end

def slow
  kw = { a: 1, b: 2, c: 3 }

  foo(1, **kw)
end

Benchmark.ips do |x|
  x.report("fast code description") { fast }
  x.report("slow code description") { slow }
  x.compare!
end

__END__

Warming up --------------------------------------
fast code description
                       108.311k i/100ms
slow code description
                        50.038k i/100ms
Calculating -------------------------------------
fast code description
                          1.596M (± 3.7%) i/s -      8.015M in   5.028700s
slow code description
                        576.682k (± 3.4%) i/s -      2.902M in   5.038684s

Comparison:
fast code description:  1596244.7 i/s
slow code description:   576682.4 i/s - 2.77x  slower