如何WinRAR的执行COM pression比检查？ [英] How does WinRAR perform a compression ratio check?

问题描述

例如。怎么能告诉一个4GB的文本文件，可以是COM pressed，比方说，200MB？很显然，它不读取所有的2秒左右的内容...所以它使用什么样的predictive算法（S）？

E.g. how can it tell that a 4GB text file can be compressed to, say, 200MB? Obviously, it doesn't read all of the contents in 2 or so seconds... so what kind of predictive algorithm(s) does it use?

推荐答案

这需要平时-log（X）+日志（2）位COM preSS x比特。然而，这是一个高度的理论价值和它天上取决于你想要的数据，以COM preSS。为你的数据，你必须记录每一个字和频率公式中插入。例如只尝试3个字符的第一位。你想寻找香农 - code。

It takes usually -log(x) + log(2) bits to compress x bits. However this is a highly theoretical value and it depends heavenly on the data you want to compress. For your data you have to record each character and frequency and insert it in the formula. For example try only 3 character first. You want to look for shannon-code.

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