超级包装。推进压缩的极限

Managing app size at Facebook is a unique challenge: Every day, developers check in large volumes of code, and each line of code translates into additional bits in the apps that people ultimately download onto their phones. Left unchecked, this added code would make the app bigger and bigger until eventually the time it takes to download would become unacceptable. Compression is one of the methods we use to keep app size minimal. These compressed files take up less space, which means smaller apps that download faster and use less bandwidth for billions of users around the world. Such savings are especially important in regions where mobile bandwidth is limited, making it costly to download large apps. But compression alone isn’t enough to keep pace with all the updates we make and features we add to our apps. So we developed a technique called Superpack, which combines compiler analysis with data compression to uncover size optimizations beyond the capability of traditional compression tools. Superpack pushes the limits of compression to achieve significantly better compression ratios than existing compression tools.

在Facebook管理应用程序的大小是一个独特的挑战：每天，开发人员检查大量的代码，每一行代码都转化为人们最终下载到手机上的应用程序中的额外位。如果不加以控制，这些增加的代码会使应用程序越来越大，直到最后它的下载时间变得不可接受。压缩是我们用来保持应用程序最小尺寸的方法之一。这些压缩文件占用更少的空间，这意味着更小的应用程序可以更快地下载，并为世界各地的数十亿用户使用更少的带宽。在移动带宽有限的地区，这种节约尤其重要，因为下载大型应用的成本很高。但是，仅靠压缩并不足以跟上我们对应用程序进行的所有更新和添加的功能。因此，我们开发了一种名为Superpack的技术，它将编译器分析与数据压缩相结合，以发现超出传统压缩工具能力的尺寸优化。Superpack挑战了压缩的极限，实现了比现有压缩工具更好的压缩率。

Over the past two years, Superpack has been able to check developer-induced app size growth and keep our Android apps small. Superpack’s compression has helped reduce the size of our fleet of Android apps, which are substantially smaller in comparison to regular Android APK compression, with average savings of over 20 percent compared with Android’s default Zip compression. Some apps that use Superpack include Facebook, Instagram, WhatsApp, and Messenger. The reduction in the size of these apps thanks to Superpack is illustrated in the table below.

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