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Facebook engineer says iOS battery drain was caused by two faults in the application's code Reuters

The Facebook app for iPhone was draining your battery because it was asking, like a small child in a car: 'Are we there yet?' and endlessly playing silent audio when the app was supposed to be closed. These are the excuses Facebook itself has given for the flawed app.

In some cases, the app had been responsible for hogging more than 80% of an iPhone's battery power, while other apps sipped less than 10%. Facebook engineering manager Ari Grant explained his team had discovered two things causing the dramatic battery drain.

"The first issue we found was a 'CPU spin' in our network code. A CPU spin is like a child in a car asking: 'Are we there yet? Are we there yet? Are we there yet?' with the question not resulting in any progress to reaching the destination." This repeated process caused the iOS app to eat up more battery power than intended, and a new version, number 42, helps reduce this cycle of endless questions.

The sound of silence

Grant went on: "The second issue is with how we manage audio sessions. If you leave the Facebook app after watching a video, the audio session sometimes stays open as if the app was playing audio silently." This is like when you close a music app to do something else, but intend for the music to keep playing, only in this case the app was playing silence."

In fairness, Facebook's recognition that users may sometimes, just every-so-often, want to leave the app is surely welcome news to us all.

"Our fixes will solve this audio issue and remove background audio completely," Grant added, meaning that, for now, you won't be able to leave audio playing from the Facebook app in the background while you look at something else. Given Facebook isn't really a platform for listening to music, we can't see this being a problem for many.

Quashing rumours that the app was draining battery life because of constant recording of where users are, Grant said: "The issues we have found are not caused by the optional Location History features in the Facebook app or anything related to location." The engineer added that, if users have not opted into the features by switching Location Access to 'always', then Facebook is not checking your location when the app is not running.

Grant ends his post by saying the company is "sorry for any inconvenience this has caused. We are committed to continuing to improve the battery usage of our app and you should see improvements in the version released today [22 October]."