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Why we don’t control screen brightness during CrXPRT 2 battery life tests

Recently, we had a discussion with a community member about why we no longer recommend specific screen brightness settings during CrXPRT 2 battery life tests. In the CrXPRT 2015 user manual, we recommended setting the test system’s screen brightness to 200 nits. Because the amount of power that a system directs to screen brightness can have a significant impact on battery life, we believed that pegging screen brightness to a common standard for all test systems would yield apple-to-apples comparisons.

After extensive experience with CrXPRT 2015 testing, we decided to not recommend a standard screen brightness with CrXPRT 2, for the following reasons:

  • A significant number of Chromebooks cannot produce a screen brightness of 200 nits. A few higher-end models can do so, but they are not representative of most Chromebooks. Some Chromebooks, especially those that many school districts and corporations purchase in bulk, cannot produce a brightness of even 100 nits.
  • Because of the point above, adjusting screen brightness would not represent real-life conditions for most Chromebooks, and the battery life results could mislead consumers who want to know the battery life they can expect with default out-of-box settings.
  • Most testers, and even some labs, do not have light meters, and the simple brightness percentages that the operating system reports produce different degrees of brightness on different systems. For testers without light meters, a standardized screen brightness recommendation could discourage them from running the test.
  • The brightness controls for some low-end Chromebooks lack the fine-tuning capability that is necessary to standardize brightness between systems. In those cases, an increase or decrease of one notch can swing brightness by 20 to 30 nits in either direction. This could also discourage testing by leading people to believe that they lack the capability to correctly run the test.

In situations where testers want to compare battery life using standardized screen brightness, we recommend using light meters to set the brightness levels as closely as possible. If the brightness levels between systems vary by more than few nits, and if the levels vary significantly from out-of-box settings, the publication of any resulting battery life results should include a full disclosure and explanation of test conditions.

For the majority of testers without light meters, running the CrXPRT 2 battery life test with default screen brightness settings on each system provides a reliable and accurate estimate of the type of real-world, out-of-box battery life consumers can expect.

If you have any questions or comments about the CrXPRT 2 battery life test, please feel free to contact us!

Justin

The CrXPRT 2 battery life test is back!

Last month, we discussed a potential fix for the error that was preventing CrXPRT 2 testers from successfully completing battery life tests on systems running Chrome v89.x and later. Since then, we’ve been testing an updated, unpublished version of the app package across several Chromebook models to ensure that the new build is stable and produces consistent results. We’re happy to report that our testing was successful, and we’ve published the new CrXPRT build (v1.2.0.0) in the Chrome Web Store and it is live as of 12:45 PM EDT today.

Note that it might take some time for the update to appear on your Chromebook and, once it does, you might have to manually approve the update notice.

Neither the tests nor the method of calculating the overall score and battery-life score in this new build have changed, so results are comparable with previous CrXPRT 2 results.

We appreciate everyone’s patience while we found a solution to the error. If you have any questions or comments about the CrXPRT 2 battery life test, please feel free to contact us!

Justin

A potential fix for the CrXPRT 2 battery life test error

For the past few months, we’ve been recommending that CrXPRT 2 testers not use the battery life test until we find a solution to a recurring error on Chrome v89.x and later. The error prevents the test from completing and producing a battery life estimate. Sometimes, the CrXPRT battery life test stops running after only a few workload iterations, while at other times, it almost reaches completion before producing the error.

We are cautiously optimistic that we’ve identified both the problem and a potential fix. We believe the problem stems from fluctuations in the time it takes the benchmark to communicate with Chrome to collect and store battery life information. While we haven’t identified the root cause of the fluctuations, adjusting the CrXPRT code to make it less sensitive to the fluctuations appears to be an effective fix. We have incorporated those adjustments into an updated, unpublished version of the app package, and we can now complete CrXPRT 2 battery life tests on Chrome v89.x and later with no failures.

We are calling this a potential fix because we’re still testing across several different Chromebook models to ensure consistency. In some testing, the variance in estimated battery life results has been a little higher than we like, so we’re taking time to determine whether that variance is present across all systems or on only specific hardware.

We’d like to apologize once again for the inconvenience that this error is causing CrXPRT 2 testers. As soon as we better understand the viability of the current fix as a long-term update, we’ll let you know!

Justin

Persistent CrXPRT 2 battery life test error on Chrome v89 and later

A few weeks ago, we discussed an error that we’d recently started encountering during the CrXPRT 2 battery life test on systems running Chrome OS v89.x and later. The error prevents the test from completing and producing a battery life estimate. CrXPRT stops running its normal workload cycle and produces a “Test Error” page. The timing of the error can vary from run to run. Sometimes, CrXPRT stops running after only a few workload iterations, while other times, the battery life test almost reaches completion before producing the error.

We have seen the error on across multiple brands of Chromebooks running Chrome OS v89.x and later. To our knowledge, Chromebooks running Chrome OS v88.x and earlier versions complete the battery life test without issues. We are unaware of any problems with the CrXPRT 2 performance test.

We’re continuing to investigate this problem. Unfortunately, we have not yet identified the root cause. Without a solution, we are recommending that for now, testers not use the CrXPRT 2 battery life test. We will post this recommendation on CrXPRT.com.

We apologize for the inconvenience that this error is causing CrXPRT 2 testers. As soon as we identify a possible solution, we will share that information here in the blog. If you have any insight into recent Chrome OS changes or flag settings that could be causing this problem, please let us know!

Justin

CrXPRT 2 battery life error on Chrome 89 and 90

In recent lab tests, we’ve encountered an error during the CrXPRT 2 battery life test that prevents the test from completing and producing a battery life estimate. As the screenshot below shows, when the error occurs, CrXPRT stops running its normal workload cycle and produces a “Test Error” page. We have seen this behavior on systems running Chrome OS v89.x and v90.x, across multiple vendor platforms. In our testing, Chromebooks running  Chrome OS v88.x and earlier versions continue to complete the battery life test without any issues.

The error occurs consistently on every Chromebook running v89.x or v90.x that we’ve tested so far. However, the timing of the error varies from run to run on the same system. Sometimes, CrXPRT stops running after only a few workload iterations, while at other times, the battery life test runs almost to completion before producing the error.

We’re actively investigating this problem, but have not yet identified the root cause. We apologize for the inconvenience that this error may be causing CrXPRT 2 testers. As soon as we identify the root cause of the problem and have ideas about possible solutions, we will share that information here in the blog. If you have any insight into recent Chrome OS changes or flag settings that could be causing this problem, please let us know!

Justin

Considering a battery life test for WebXPRT 4

A few weeks ago, we discussed the beginnings of a WebXPRT 4 development plan, and asked for reader feedback about potential workload changes. So far, the two most common feedback topics have been the possible addition of a WebAssembly workload, and the feasibility of including a browser-based battery life test. Today, we discuss what a WebXPRT 4 battery life test would look like, and some of the challenges we’d have to overcome to make it a reality.

Battery life tests fall into two primary categories: simple rundown tests and performance-weighted tests. Simple rundown tests measure battery life during extreme idle periods and loops of movie playbacks, etc., but do not reflect the wide-ranging mix of activities that characterize a typical day for most users. While they can be useful for performing very specific apple-to-apples comparisons, these tests have limited value when it comes to giving consumers a realistic estimation of the battery life they would experience during everyday use.

In contrast, performance-weighted battery life tests, such as the one in CrXPRT 2, attempt to reflect real-world usage. The CrXPRT battery life test simulates common daily usage patterns for Chromebooks by including all the productivity workloads from the performance test, plus video playback, audio playback, and gaming scenarios. It also includes periods of wait/idle time. We believe this mixture of diverse activity and idle time better represents typical real-life behavior patterns. This makes the resulting estimated battery life much more helpful for consumers who are trying to match a device’s capabilities with their real-world needs.

From a technical standpoint, WebXPRT’s cross-platform nature presents us with several challenges that we did not face while developing the CrXPRT battery life test for Chrome OS. While the WebXPRT performance tests run in almost any browser, cross-browser differences in battery life reporting may restrict the battery life test to a single browser. For instance, Mozilla has deprecated the battery status API for Firefox, and we’re not yet sure if there’s another approach that would work. If a WebXPRT 4 battery life test supported only a single browser, such as Chrome or Safari, would you still be interested in using it? Please let us know.

A browser-based battery life workflow also presents other challenges that we do not face in native client applications such as CrXPRT:

  • A browser-based battery life test would require the user to check the starting and ending battery capacities, with no way for the app to independently verify data accuracy.
  • The battery life test could require more babysitting in the event of network issues. We can catch network failures and try to handle them by reporting periods of network disconnection, but those interruptions could influence the battery life duration.
  • The factors above could make it difficult to achieve repeatability. One way to address that problem would be to run the test in a standardized lab environment lab with a steady internet connection, but a long list of standardized environmental requirements would make the battery life test less attractive and less accessible to many testers.

Our intention with today’s blog is not to make a WebXPRT 4 battery life test seem like an impossibility. Rather, we want to share our perspective on what the test might look like, and describe some of the challenges and considerations in play. If you have thoughts about battery life testing, or experience with battery life APIs in one or more of the major browsers, we’d love to hear from you!

Justin

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