dup_bench.exs

Benchfella.start duration: 1.0#, format: :machine

defmodule StringDuplicateBench do
  use Benchfella

  @iterations [100, 1000, 10000, 100000]
  Enum.each(@iterations, fn n ->
    @str "1234567890"
    @n n

    bench "binary copy #{n}" do
      :binary.copy(@str, @n)
    end

    bench "strdup #{n}" do
      strdup(@str, @n)
    end

    bench "List.duplicate #{n}" do
      List.duplicate(@str, @n)
    end

    bench "iodata #{n}" do
      iodatadup(@str, @n)
    end

    bench "iodata square #{n}" do
      iodatasquaredup(@str, @n)
    end

    bench "iodata to binary #{n}" do
      IO.iodata_to_binary(iodatadup(@str, @n))
    end

    bench "iodata square to binary #{n}" do
      IO.iodata_to_binary(iodatasquaredup(@str, @n))
    end
  end)

  def iodatadup(_, 0), do: []
  def iodatadup(str, n), do: [str|iodatadup(str, n-1)]

  # The same idea as in fast exponentiation by squaring is used here
  
  def iodatasquaredup(_, 0), do: []
  def iodatasquaredup(str, 1), do: [str]

  def iodatasquaredup(str, n) when rem(n, 2) == 0 do
    tmp = iodatasquaredup(str, div(n, 2))
    [tmp|tmp]
  end

  def iodatasquaredup(str, n) do
    [str|iodatasquaredup(str, n-1)]
  end


  def strdup(_, 0), do: ""
  def strdup(str, 1), do: str

  def strdup(str, n) when rem(n, 2) == 0 do
    tmp = strdup(str, div(n, 2))
    tmp <> tmp
  end

  def strdup(str, n) do
    str <> strdup(str, n-1)
  end
end

results

StringDuplicateBench.iodata square 100:                10000000   0.29 µs/op
StringDuplicateBench.binary copy 100:                  10000000   0.40 µs/op
StringDuplicateBench.iodata square 1000:               10000000   0.50 µs/op
StringDuplicateBench.iodata square 10000:              10000000   0.62 µs/op
StringDuplicateBench.iodata square 100000:             10000000   0.80 µs/op
StringDuplicateBench.List.duplicate 100:               10000000   0.96 µs/op
StringDuplicateBench.strdup 100:                        1000000   1.11 µs/op
StringDuplicateBench.iodata square to binary 100:       1000000   1.32 µs/op
StringDuplicateBench.iodata 100:                        1000000   1.47 µs/op
StringDuplicateBench.iodata to binary 100:              1000000   2.18 µs/op
StringDuplicateBench.strdup 1000:                       1000000   2.20 µs/op
StringDuplicateBench.binary copy 1000:                   500000   2.92 µs/op
StringDuplicateBench.List.duplicate 1000:                500000   7.39 µs/op
StringDuplicateBench.strdup 10000:                       200000   7.66 µs/op
StringDuplicateBench.iodata square to binary 1000:       100000   10.61 µs/op
StringDuplicateBench.iodata 1000:                        100000   13.06 µs/op
StringDuplicateBench.iodata to binary 1000:              100000   18.74 µs/op
StringDuplicateBench.binary copy 10000:                  100000   29.19 µs/op
StringDuplicateBench.strdup 100000:                       50000   65.22 µs/op
StringDuplicateBench.List.duplicate 10000:                20000   88.81 µs/op
StringDuplicateBench.iodata square to binary 10000:       10000   108.81 µs/op
StringDuplicateBench.iodata 10000:                        10000   129.40 µs/op
StringDuplicateBench.iodata to binary 10000:              10000   188.71 µs/op
StringDuplicateBench.binary copy 100000:                  10000   284.83 µs/op
StringDuplicateBench.List.duplicate 100000:                2000   811.83 µs/op
StringDuplicateBench.iodata square to binary 100000:       2000   970.95 µs/op
StringDuplicateBench.iodata 100000:                        1000   1406.83 µs/op
StringDuplicateBench.iodata to binary 100000:               500   3579.47 µs/op