Mathematics & Physics 2015, 8(4), 497–501 УДК 519.686 Simple Essential Improvements to the ROUGE-W Algorithm Sergej V. Znamenskij∗ Ailamazyan Program Systems Institute of RAS Peter the First Street, 4, Veskovo village Pereslavl area, Yaroslavl region, 152021 Russia Received 10.10.2015, received in revised form 01.11.2015, accepted 16.11.2015 The ROUGE-W algorithm to calculate the similarity of texts is referred in more than 500 scientific publications since 2004. <...> The power of the algorithm depends on the weight function choice. <...> An optimal selection of the weight function is studied. <...> Simple changes are described to ensure the expected result. <...> Keywords: sequence alignment, longest common subsequence, ROUGE-W, edit distance, string similarity, optimization, complexity bounds. <...> String is the finite sequence of letters X = (x1, . . . ,xn) that can be considered as a function X: 1,n→Σ returning a letter located at the given position. <...> The well known sequence alignment problem is to find the most valuable common subsequence for any given strings. <...> A common subsequence P became the Longest Common Subsequence (LCS) if "the most valuable" means "with the maximal possible length k". <...> Since 70th it is well known that such meaning does not meet practical needs [1]: when alignment intended to identify common part and difference in computer logs, LCS often finds unnaturally fragmented common part bearing a lot of frequently used letters being sporadically aligned. <...> For example, the option pbe a refversenced being revfersenced has the common sequence of the length equal to 11 against of only 10 symbols observed for be a reversed preference being reversed that is much better for text editing. <...> A lot of other applications (partially mentioned in [2]) make reason to consider a long string or a chain of close longer strings to be preferably found in a common part than just a long list of very short senseless matches as in this example of edit distance for texts. <...> Comparison of string (A) to strings (B) and (C) shown below (A) preference being reversed, ∗svz@latex.pereslavl.ru ⃝ Siberian Federal University. <...> All rights reserved c – 497 – Sergej V. Znamenskij (B) be a reversed <...>