Update: Over the course of the evening, ROM Manager was updated yet again, to version 5.5.2.0 - this time adding support for the TWRP recovery, which is undoubtedly a feature many users have been wanting for some time. Just update ROM Manager in the Play Store and you'll have it.

ROM Manager, one of the most useful and versatile tools available for a consummate ROM-flasher, got an update today, bringing the app up to version 5.5.1.9. The update brings just two changes – a bug fix, and something much more significant: support for delta downloads.

For those who are unfamiliar with the term, "delta downloads" are like the Play Store's smart updates, CyanogenMod's built-in update system, or the files users can download with CyanDelta – bite-size update files that only pack the things that have changed since your ROM's last build. Using delta updates decreases download times, data usage, and hassle in keeping your ROM on the bleeding edge.

deltaprocessing delta

Images: Koushik Dutta

Want to know how it works? In a post to Google+, ROM Manager's developer Koushik Dutta explains all. Essentially, when the user chooses to download a delta update, a list of other zip files downloaded by ROM Manager is sent to a delta server. The server then creates an "edge frequency graph" to determine what exactly has changed between the zip files. Then, "the edges (deltas) with the highest frequency are prioritized for delta creation on the server." Sound complicated? Luckily, you won't have to think about any of this, as the whole process executes pretty smoothly. If the delta update fails, ROM Manager will fall back to the latest full zip file.

Koush warns that this (awesome) functionality is "probably super buggy and beta," but promises plenty of work on bugs, and further streamlining of the process once the feature is "fully baked." To grab the update, just hit the widget below. For more info, check out Koush's post on Google+.

Source: Google+