Figure 9

Compression efficiency (data size). We calculate the compression efficiency of 7z when the size of the original data \(S_o\) gradually increases. Here, \(r_c\) of 7z is 0.34 when a text file in size of 500 MB is compressed. Given that \(S_T\) of 7z is 201 KB, we have the results as shown in (a) where \(e_c\)s are calculated for the data storage method in ideal case by \(e_c =1-r_c= 0.66\) and in the self-containment case by \(e_c = 1 - (r_c \times S_o + 201K)/S_o\). To validate the results, we further pack a set of test data files with different types (e.g., txt, jpg, exe, mp3) in a single compressed package and compare their actual values of \(e_c\) with a fixed \(r_c=0.34\) as shown in (b). The results are roughly consistent with those in calculation as shown in (a).