How can we easily time function calls in elixir?

Question

How can we easily time function calls in Elixir?

Is there any hidden switch in IEx to enable this?

I don't think there's an option to do that. Probably the easier and quickest way to do that is Erlang's timer:tc/1-2-3. — whatyouhide
@whatyouhide not sure what i'm doing wrong iex(54)> :timer.tc(Demo.sum 1000) ** (BadFunctionError) expected a function, got: 500500 (stdlib) timer.erl:165: :timer.tc/1 — Charles Okwuagwu
as you can see in the documentation for timer:tc/1 I linked in the previous comment, if you're only passing one argument to timer:tc it has to be a function. Your example would be :timer.tc(fn -> Demo.sum(1000) end). If you want to pass a module+function+arguments triplet, just go with :timer.tc(Demo, :sum, [1000]). — whatyouhide

Overbryd Overbryd · Accepted Answer · 2015-04-16T12:24:36

You can write a module¹ that can measure a given function. The following function returns the runtime of a given function in seconds:

defmodule Benchmark do
  def measure(function) do
    function
    |> :timer.tc
    |> elem(0)
    |> Kernel./(1_000_000)
  end
end

Use it like this:

iex> Benchmark.measure(fn -> 123456*654321 end)
9.0e-6

If you want to use that for Benchmarking, then there is another answer.

A better approach than measuring single run execution time is to measure operations per timeframe. This takes the code under test and executes it repeatingly within a given timeframe. This methodology yields more accurate results.

There is a library called Benchwarmer you can use for that:

Add Benchwarmer to your mix.exs

def deps do
  [ { :benchwarmer, "~> 0.0.2" } ]
end

Simply pass an inline function:

iex> Benchwarmer.benchmark fn -> 123456*654321 end
*** #Function<20.90072148/0 in :erl_eval.expr/5> ***
1.2 sec     2M iterations   0.61 μs/op

[%Benchwarmer.Results{...}]

[1]: Code taken from http://www.littlelines.com/blog/2014/06/27/elixir-vs-ruby-showdown-part-one/
Benchee https://github.com/bencheeorg/benchee

How can we easily time function calls in elixir?

1 Answers