Abstract
Kolmogorov complexity measures the amount of information in a string as the size of the shortest program that computes the string. The Kolmogorov structure function divides the smallest program producing a string in two parts: the useful information present in the string, called sophistication if based on total functions, and the remaining accidental information. We formalize a connection between sophistication (due to Koppel) and a variation of computational depth (intuitively the useful or nonrandom information in a string), prove the existence of strings with maximum sophistication and show that they are the deepest of all strings.
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Preliminary version of this paper appeared in the Proceedings of the 30th ICALP Conference (Lecture Notes in Computer Science, vol. 2719, pp. 267–277. Springer, Berlin, 2003). Much of the research for this paper occurred at the NEC Research Institute. Luís Antunes is partially supported by KCrypt (POSC/EIA/60819/2004) and funds granted to LIACC through the Programa de Financiamento Plurianual, Fundação para a Ciência e Tecnologia and Programa POSI.
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Antunes, L., Fortnow, L. Sophistication Revisited. Theory Comput Syst 45, 150–161 (2009). https://doi.org/10.1007/s00224-007-9095-5
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DOI: https://doi.org/10.1007/s00224-007-9095-5