README.md

Benchmark.js in Elm

This repo provides a library for writing console-based Benchmark.js tests in Elm.

Getting Started

Before you begin, you must pull in both the node.js dependencies (jsdom and benchmark):

$ cabal install
$ npm install benchmark
$ npm install jsdom

(On Windows, jsdom is somewhat difficult to install. Refer to this blog post for detailed instructions)

Example

Each test must be an outgoing port of type () -> (). Define any number of these () -> () tests in a module named Benchmark. Here's an example:

-- Test.elm
module Benchmark where

discard : a -> ()
discard _ = ()

port testAdd10 : () -> ()
port testAdd10 = \_ -> discard <| n + 10

That's all the Elm you need. Compile and run it with:

$ elm-benchmark Test.elm test.js
Generating JavaScript ... Done
Making exe

$ node test.js
testAdd10 x 22,790,539 ops/sec ±0.31% (98 runs sampled)

And you can see the benchmark test results.

For more complicated functions, you can set them up as functions that take a dummy () and return a dummy (), as we don't care about the actual value. Elm is strictly evaluated, so even if we discard the result of a function call, it will still execute. Here's an example:

module Benchmark where

import Dict
import List

-- Helper function to discard results
discard : a -> ()
discard _ = ()

-- Test setup
list = List.zip [1..1000] [1..1000]

-- Benchmark tests:
port testDictFromList : () -> ()
port testDictFromList = \_ -> discard << Dict.fromList <| list

Again, compile and run it with:

$ elm-benchmark Test.elm test.js
Generating JavaScript ... Done
Making exe

$ node test.js
testDictFromList x 50.91 ops/sec ±0.37% (68 runs sampled)

Command Line Interface

The basic interface is elm-benchmark infile outfile, where infile is an Elm source file to compile and outfile is the resulting JavaScript file to be run with node. The infile module MUST be Benchmark, that is to say that the source file must have module Benchmark where as the first line. This restriction may be lifted in the future.