Autom Softw Eng DOI 10.1007/s10515-017-0213-6 Exact search-space size for the refactoring scheduling problem Rodrigo Morales 1 · Francisco Chicano 2 · Foutse Khomh 1 · Giuliano Antoniol 1 Received: 23 September 2016 / Accepted: 30 January 2017 © Springer Science+Business Media New York 2017 Abstract Ouni et al. “Maintainability defects detection and correction: a multi- objective approach” proposed a search-based approach for generating optimal refactoring sequences. They estimated the size of the search space for the refactoring scheduling problem using a formulation that is incorrect; the search space is estimated to be too much larger than it is. We provide in this paper the exact expression for com- puting the number of possible refactoring sequences of a software system. This could be useful for researchers and practitioners interested in developing new approaches to automate refactoring. Keywords Software maintenance · Search-based software engineering · Refactoring 1 Introduction Refactoring is a software maintenance activity that aims to improve code design, while preserving behavior (Opdyke 1992). In the last decade, many works have reported that B Rodrigo Morales rodrigomorales2@acm.org Francisco Chicano chicano@lcc.uma.es Foutse Khomh foutse.khomh@polymtl.ca Giuliano Antoniol antoniol@ieee.org 1 DGIGL, Polytechnique Montréal, Montreal, Canada 2 Dept. de Lenguajes y Ciencias de la Computación, Universidad de Málaga, Andalucía Tech, Málaga, Spain 123