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Hello guys

I need an explanation of how adaptive methods work. especially this. word: abrakadabra compress : abr[3,1]k[2,1]d[7,4] Why is this so?

12th Apr 2023, 5:41 PM
Matej
+ 4
Adaptive methods, in the context of data compression, refer to algorithms that dynamically adjust their encoding strategy based on the specific characteristics of the input data. These methods often use statistical models of the input data to predict the probability of the next symbol in the input stream and use that prediction to select an appropriate code for that symbol. In the example you provided, the input word "abrakadabra" has been compressed using a specific adaptive compression method that uses a technique called run-length encoding. The compressed representation consists of a sequence of pairs, where each pair represents a run of identical symbols in the input. Specifically, the first element in each pair represents the length of the run, and the second element represents the index of the first occurrence of the symbol in the run.
13th Apr 2023, 7:35 AM
+ 4
To illustrate this, let's consider the first run in the input, which consists of three consecutive 'a' characters. The compressed representation for this run is [3,1], which indicates that there are three 'a' characters starting at index 1 in the input string. The next run is a single 'b' character at index 4, which is encoded as [1,4]. The third run is a single 'r' character at index 5, which is encoded as [1,5]. The fourth run consists of two 'a' characters at indices 6 and 8, which is encoded as [2,6]. Finally, the fifth run consists of a single 'k' character at index 7, which is encoded as [1,7], and the last run consists of four 'd' characters starting at index 9, which is encoded as [4,9].
13th Apr 2023, 7:36 AM
+ 4
Overall, the compressed representation [3,1]k[2,1]d[7,4] represents the original input word "abrakadabra" using fewer symbols by exploiting the repeated patterns in the input. This compression technique is effective for data with long runs of identical symbols, but may not be optimal for other types of input data
13th Apr 2023, 7:36 AM