README.md - external/github.com/WebKit/Speedometer - Git at Google

 # What is Speedometer?

 Speedometer is a benchmark for web browsers that measures Web application responsiveness
 by timing simulated user interactions on various workloads. Our primary goal is to make it
 reflect the real-world Web as much as possible. When a browser improves its score on the
 benchmark, actual users should benefit. In order to achieve this, it should:

 -   Test end-to-end user journeys instead of testing specific features in a tight loop. Each
     test should exercise the full set of what’s needed from the engine in order for a user to
     accomplish a task.
 -   Evolve over time, adapting to the present Web on a regular basis. This should be informed
     by current usage data, and by consensus about features which are important for engines to
     optimize to provide a consistent experience for users and site authors.
 -   Be accessible to the public and useful to browser engineers. It should run in every modern
     browser by visiting a normal web page. It should run relatively quickly, while providing
     enough test coverage to be reflective of the real-world Web.

 # Score and Test Measurement

 Each test can contain several steps who contributed to the test duration. Note that the prepare step of a test is _unmeasured_ and thus does not contribute to the score. All following test
 steps are **measured** and summed up in the test step time.

 <img  src="./resources/measurement-timeline.svg" />

 Each step consists of the following phases:

 <dl>
     <dt>Sync:</dt>
     <dd>Time spent in synchronous JS execution.</dd>
     <dt>Async:</dt>
     <dd>Time spent in asynchronous JS like Promise or setTimeout tasks scheduled by the sync-step.</dd>
 </dl>

 ## Score

 The final benchmark score is calculated based of the inverse of [geomean](https://en.wikipedia.org/wiki/Geometric_mean) of all tests. We average the score over multiple iterations with the [arithmetic mean](https://en.wikipedia.org/wiki/Arithmetic_mean). By using the geomean to combine the test durations we maintain the invariant that relative improvements are favoured equally amongst all tests, even though they can have vastly different durations.

 <img  src="./resources/score.svg" />
	# What is Speedometer?

	Speedometer is a benchmark for web browsers that measures Web application responsiveness
	by timing simulated user interactions on various workloads. Our primary goal is to make it
	reflect the real-world Web as much as possible. When a browser improves its score on the
	benchmark, actual users should benefit. In order to achieve this, it should:

	- Test end-to-end user journeys instead of testing specific features in a tight loop. Each
	test should exercise the full set of what’s needed from the engine in order for a user to
	accomplish a task.
	- Evolve over time, adapting to the present Web on a regular basis. This should be informed
	by current usage data, and by consensus about features which are important for engines to
	optimize to provide a consistent experience for users and site authors.
	- Be accessible to the public and useful to browser engineers. It should run in every modern
	browser by visiting a normal web page. It should run relatively quickly, while providing
	enough test coverage to be reflective of the real-world Web.

	# Score and Test Measurement

	Each test can contain several steps who contributed to the test duration. Note that the prepare step of a test is _unmeasured_ and thus does not contribute to the score. All following test
	steps are measured and summed up in the test step time.

	<img src="./resources/measurement-timeline.svg" />

	Each step consists of the following phases:

	<dl>
	<dt>Sync:</dt>
	<dd>Time spent in synchronous JS execution.</dd>
	<dt>Async:</dt>
	<dd>Time spent in asynchronous JS like Promise or setTimeout tasks scheduled by the sync-step.</dd>
	</dl>

	## Score

	The final benchmark score is calculated based of the inverse of [geomean](https://en.wikipedia.org/wiki/Geometric_mean) of all tests. We average the score over multiple iterations with the [arithmetic mean](https://en.wikipedia.org/wiki/Arithmetic_mean). By using the geomean to combine the test durations we maintain the invariant that relative improvements are favoured equally amongst all tests, even though they can have vastly different durations.

	<img src="./resources/score.svg" />