Proving Divide and Conquer Complexities in Isabelle/HOL
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- Eberl, M. J Autom Reasoning (2017) 58: 483. doi:10.1007/s10817-016-9378-0
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The Akra–Bazzi method (Akra and Bazzi in Comput Optim Appl 10(2):195–210, 1998. doi:10.1023/A:1018373005182), a generalisation of the well-known Master Theorem, is a useful tool for analysing the complexity of Divide and Conquer algorithms. This work describes a formalisation of the Akra–Bazzi method (as generalised by Leighton in Notes on better Master theorems for divide-and-conquer recurrences, 1996. http://courses.csail.mit.edu/6.046/spring04/handouts/akrabazzi.pdf) in the interactive theorem prover Isabelle/HOL and the derivation of a generalised version of the Master Theorem from it. We also provide some automated proof methods that facilitate the application of this Master Theorem and allow mostly automatic verification of \(\varTheta \)-bounds for these Divide and Conquer recurrences. To our knowledge, this is the first formalisation of theorems for the analysis of such recurrences.